SB555 Development Kit Hardware Integration Guide Proprietary and Confidential 2130075 Rev 1.
Preface Important Notice Safety and Hazards Because of the nature of wireless communications, transmission and reception of data can never be guaranteed. Data may be delayed, corrupted (i.e., have errors) or be totally lost.
SB555 Hardware Integration Guide The driver or operator of any vehicle should not operate the Sierra Wireless modem while in control of a vehicle. Doing so will detract from the driver or operator's control and operation of that vehicle. In some states and provinces, operating such communications devices while in control of a vehicle is an offence. Note: Some airlines may permit the use of cellular phones while the aircraft is on the ground and the door is open.
Preface Patents Portions of this product are covered by some or all of the following US patents: 5,515,013 5,617,106 5,629,960 5,682,602 5,748,449 5,845,216 5,847,553 5,878,234 5,890,057 5,929,815 6,169,884 6,191,741 6,199,168 6,327,154 6,339,405 D367,062 D372,248 D372,701 D416,857 D442,170 D452,495 D452,496 and other patents pending. This product includes technology licensed from: Copyright Trademarks ©2002 Sierra Wireless, Inc. All rights reserved. Printed in Canada.
SB555 Hardware Integration Guide Contact Information Sales Desk: Phone: 1-604-232-1488 Hours: 8:00 AM to 5:00 PM Pacific Time e-mail: sales@sierrawireless.com Technical Support: Included with the purchase of the SB555 Development Kit you receive five hours of tier 3 engineering integration support. You will have received instructions by e-mail on how to access the OEM Customer Support web site. For more details, please contact your account manager, or the Sierra Wireless sales desk.
Table of Contents About this Guide. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Document structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Terminology and acronyms . . . . . . . . . . . . . . . . . . . . . . . . 13 Conventions . . . . . . . . . . . . . .
Hardware Integration Guide Electrical Integration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Modem specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Location of pin 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 General requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Unused pins. . . .
Contents Serial Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Serial port specifications . . . . . . . . . . . . . . . . . . . . . . . . . . External pullup and pulldown resistors . . . . . . . . . . . . . . ESD protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 37 38 39 Primary port . . . . . . . . . . . . . . . . . . . . . . . . . .
Hardware Integration Guide Port configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Secondary port sample integration . . . . . . . . . . . . . . . . . . 54 Minimum integration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Voice Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Introduction to voice features . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Audio block diagram . . . . . . . . . . . . . . . .
Contents Machine interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Sample machine interface to status outputs . . . . . . . . . 72 Shutdown and reset control. . . . . . . . . . . . . . . . . . . . . . . . . . . Pin 37: /Shdn_Ack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pin 38: /ShutDown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pin 39: /Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hardware Integration Guide Appendix A: Host Connector Pinouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Appendix B:Sample Integration . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 Appendix C: Electrostatic Discharge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Charge creation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1: About this Guide • Introduction • Document structure • References • Conventions 1 Introduction This guide is one component of the SB555 Development Kit. It covers the integration of the product from the hardware point of view. Other guides in the kit cover project planning, software integration, and product verification and configuration. For details on the features of the SB555 embedded modem, please consult the SB555 Embedded Modem Product Specification (document #2130072).
SB555 Hardware Integration Guide Document structure This document covers hardware integration issues in these main categories: • Mechanical Integration · Mounting · Connectors · Environmental Issues • Electrical Integration · General Specifications · General Considerations · Power Supply · Electrostatic Discharge (ESD) • Serial Interface · Primary Port (Serial 1) - Data · Secondary Port (Serial 2) - Control • Voice Interface · Analog Voice • Control Signals · Status Signals · Shutdown Control · Reset • RF
About This Guide References This guide covers only the hardware integration of the SB555 modem. It does not deal with specifics of product modem operation or use of the optional Embedded Modem Interface Kit. Please consult the other documents provided with the Development Kit or the Interface Kit User Guide for additional information on operations. You may also want to consult other documents available on our Internet site at www.sierrawireless.com.
SB555 Hardware Integration Guide Units Units of measure are given in metric. Where measure is provided in imperial units, they are shown in parenthesis after the metric units. Signal Names When signals are discussed by their function, the functional name is used in standard font (i.e. Reset, Shutdown Acknowledge).
2: Mechanical Integration • Introduction • Physical dimensions • Mounting • Connectors • Assembly sequence • Environmental issues 2 Introduction The SB555 CDMA2000 1X embedded modem form factor is the proprietary Sierra Wireless embedded module package. Physical dimensions, mounting holes, and connectors are identical to other upcoming Sierra Wireless embedded modem products.
SB555 Hardware Integration Guide Physical dimensions The SB555 comes in the Sierra Wireless proprietary standard module package. Dimensions in millimeters are shown in the figure below.
Mechanical Integration Mounting the module Note: The integration should include standoffs of some kind to protect the modem shields from being crushed during assembly and from coming into contact with circuitry on the host device. Sierra Wireless embedded modules have four (4) mounting holes of 2.5 mm (0.984”) diameter, one located at each corner of the module (as seen in Figure 2-1). The mounting holes are sized to accommodate a metric M2 (#2 screw).
SB555 Hardware Integration Guide Module weight The module has a total weight under 14 grams (0.49 ounces). Typical weight is 13.5 grams (0.48 ounces). Module shields The SB555 comes with shields on both top and bottom. These shields are attached to a fence surrounding the circuitry. Figure 2-3: Shield fence frame The internal webbing of the fence frame may be removed in some units to permit factory rework.
Mechanical Integration place only. The product has been fully qualified mechanically and electrically with and without the webbing. Module connectors There are two connectors: a 40-pin header for the host interface, and an MMCX connector for the antenna. Both are mounted offset from the module centerline to prevent assembly orientation errors. Host interface connector The host connector is a 40-pin, 1 mm pitch, 2-row, female header (Samtec part #CLM-120-02F-n-BE with bottom entry option).
SB555 Hardware Integration Guide Location of pin 1 Pin 1 of the host connector is shown in Figure 2-4. When viewing the module with the connector facing up and the RF connector at the bottom, pin 1 is on the extreme right of the inside edge (lower row). Pin 40 Pin 2 Pin 39 Pin 19 Pin 1 Figure 2-4: Host connector pin locations Antenna connector The antenna connector is an MMCX female jack oriented in line with the module longitudinal axis. Mating plugs can be either straight or rightangle.
Mechanical Integration For mechanical integration, use a flexible 50 Ω coaxial cable to allow attachment of the MMCX connector to the modem either before or after mounting the module on the host device. Assembly sequence Due to the strong detent in the MMCX antenna connector, Sierra Wireless recommends that you connect the antenna cable to the modem before connecting the modem’s 40-pin connector to the host device. This will avoid stress on the host connector.
SB555 Hardware Integration Guide Table 2-1: Environmental specifications Temperature range Operating: -30 to +60°C (-22 to +140°F) (modem ambient*) Storage: -40 to +85°C (-40 to +185°F) Humidity MIL-STD-202F 95% non-condensing @ 65°C (149°F) Vibration (random)** MIL-STD-810E 0.04 g2/Hz, 10 – 2000 Hz Vibration (sine wave)** PC Card Standard 15 g (147 m/s2), 10 – 2000 Hz Shock** MIL-STD-202F 50 g (490 m/s2), 11 ms, 6 pulses/axis Drop** (unpackaged) PC Card Standard 0.
Mechanical Integration Table 2-2 provides a guideline of the energy to be dissipated when the modem is in various states of activity. Table 2-2: Energy dissipation (typical) Mode Current consumption Energy to dissipate Shutdown 3.3 V @ 0.7 mA 2.3 mW Slotted sleep (SCI = 2) (DTR deasserted) 3.3 V @ 5 mA 16.5 mW Slotted sleep (SCI = 2) (DTR asserted) 3.3 V @ 40 mA 132 mW Receive 3.3 V @ 160 mA 528 mW Transmit (typical at +3 dBm) 3.
SB555 Hardware Integration Guide Shock and vibration The specifications provided on shock and vibration are for the module free of integration hardware. A person rolling off a bed onto the floor is likely to emerge without injury; whereas one with a fire hydrant strapped to his back may not. Once integrated into your device, the surrounding hardware can have a significant impact on the modem’s survivability.
3: Electrical Integration • Introduction • Specifications • General requirements • Power supply • Electrostatic discharge 3 Introduction This chapter covers the integration requirements and issues related to the general electrical connection of the SB555 modem, and the power supply in particular. RF issues are covered in Chapter 7:RF Integration on page 79. The SB555 embedded modem presents all electrical interfaces on the single 40-pin host connector.
SB555 Hardware Integration Guide Table 3-1: Host interface electrical characteristics Parameter Test Conditions Min Typical Max Units Power Vcc DC supply Max ripple 100 mVp-p 3.2 3.3 4.2 V Digital Interface VIH HI threshold 2.1 3.0 3.3 V VIL LO threshold 0 0 0.8 V IIH Input current 3 V applied to input 0 120 µA IIL Input current 0 V applied to input 0 -120 µA VOH HI output IOH = 2.0 mA 2.4 3.0 V VOL LO output IOL = -2.0 mA 0 0.
Electrical Integration General requirements Unused pins Unused signals must be terminated properly. The pinout tables, both in the Appendix and in the interface sections, include a column for termination of unused pins. Preventing back-power when the modem is off Note: Without proper input protection, the modem may draw sufficient current to remain powered, even when the normal supply power is removed. Active low signals may be deasserted (driven high) by the host device when the modem is not needed.
SB555 Hardware Integration Guide Voltage regulation and buffering All logic signals at the SB555 host connector are referenced to 3.0 V. Logic signals at the host device may be referenced to 3.3 V, thus requiring the use of buffers between the devices. These buffers are discussed in the sections on the specific interfaces. See the Typical MCU Integration block diagram in the appendix. Note: The actual VCC of the logic internal to the SB555 is 3.0 V, not the 3.2 V–4.
Electrical Integration Note: Floating signal lines can be noisy, and increase power consumption. If a host reset configures any of its I/O pins (controlling outputs to the modem: DTR1, /RTS1, TxD1, /RTS2, TxD2, /ShutDown, MdmReset) as an input, and the pin does not have any internal pullup or pulldown device, use a pulldown resistor to prevent the line from floating. A suggested value is 100 kΩ. Electrostatic discharge You are responsible for any ESD protection on digital circuits.
SB555 Hardware Integration Guide Pins 25 and 30 are included to provide a connection to ground near the pins for the two serial ports. The electrical characteristics of the power supply are: • Max ripple: 100 mVp-p (1 Hz – 100 kHz) • Minimum: 3.20 V • Typical: 3.30 V • Maximum: 4.20 V Current consumption The current consumption of the modem varies considerably on the usage model of your device. Consult the Design Guide (document #2130179) for assistance in planning your requirements.
Electrical Integration For the SB555 modem to maintain a clean RF signal, it is essential that the power supply also be clean. Ensure the supply power is as free of noise as possible. Figure 3-2: Power interface block diagram Rev 1.0 Apr.
SB555 Hardware Integration Guide MOSFET power switch Note: This mechanism is needed to follow the recommended shutdown sequence prior to removing power from the modem. The MOSFET power switch is recommended to provide the host device with software control of the power to the SB555 modem. A suggested part is SI2305DS from Siliconix (www.vishay.com/ brands/siliconix/).
Electrical Integration If the LEDs were connected directly to a VBATT of 4.2 V, the voltage at the /Status pins could exceed the limit of VCC + 0.3 V, possibly damaging the modem. There could also be constant leakage current, draining the battery. This will depend on the voltage drop across the selected LEDs. Similarly, if the buffer were powered by a VBATT greater than 3.30 V, the voltage at the input pins of the SB555 would also exceed the VCC + 0.3 V limit. Use a 3.
SB555 Hardware Integration Guide Requirements of the power interface Module shielding The module is fully shielded to protect against EMI and to ensure FCC regulatory compliance. To maintain the shield effectiveness the modem shields must not be removed and must not be connected to the host ground. Ground loops must be avoided. See “Ground plane isolation” on page 81. Power ramp-up The SB555 modem will hold the circuitry in reset until stable power is established. When the voltage reaches 2.
Electrical Integration Power-up timing After release from reset, the modem performs a self test and initialization. It begins normal operation within 7–15 seconds. All serial port signals should be considered undefined or invalid until both /DSR1 and /CTS1 are asserted. Only at that time is the modem ready for use. Figure 3-4: Control signal timing • t0—Reset is released. • t1—After self test, initialization begins. /DCD1 may change state based on its condition at the time of the reset.
SB555 Hardware Integration Guide Trace widths Ensure that the PCB trace widths to the SB555 VCC and GND pins are sufficient for a maximum current of 900 mA. Consult the Design Guide (document #2130179) for details on current consumption in all modes. Do not connect the modem package shield to GND or AGND.
4: Serial Interfaces • Introduction • Primary port • Secondary port 4 Introduction The SB555 CDMA2000 1X embedded modem presents two serial port interfaces. • Primary port—the basic modem interface offering AT command and user data I/O • Secondary port—for modem management using a Sierra Wireless proprietary CnS (Control and Status) protocol This chapter deals with the electrical integration of each of these two serial ports.
SB555 Hardware Integration Guide Table 4-1: Serial interface electrical characteristics Parameter Conditions Min Typ. Max Units 2.1 3.0 3.3 V 0 0.8 V Digital Interface VIH HI threshold VIL LO threshold IIH Input current 3 V applied input 10 120 µA IIL Input current 0 V applied input 0 -120 µA VOH HI output IOH = 1.0 mA 2.0 VOL LO output IOL = -1.0 mA IOH Output current VOH > 2.0 V IOL Output current VOL < 1.0 V 0 0 3.0 V 0.4 V 3.0 mA -3.
Serial Interfaces If integrating to an MCU, and its reset configures any of its I/O pins (controlling outputs to /DTR1, /RTS1, or TxD1) as an input, and the pin does not have any internal pullup or pulldown device, use a pulldown resistor to prevent the line from floating. Floating signal lines can be noisy, and increase power consumption. A suggested value is 100 kΩ. ESD protection You are responsible for any ESD protection on digital circuits.
SB555 Hardware Integration Guide Primary port The primary serial port pins (Serial 1) comprise a standard set of serial data and handshaking (control) lines. Signals must be terminated properly if they are not used.
Serial Interfaces Note: If your application intends to use Windows ACPI, then both DTR and RI are required signals. The remaining primary port control lines (DCD, DTR, DSR, and RI) are, strictly speaking, not needed; however they are desirable in most applications. The SB555 modem is designed to use all control signals of the serial interface. The recommended integration is to use the full family of controls to provide the greatest functionality.
SB555 Hardware Integration Guide Pin 23: TxD1 This is the data channel from the host to the modem (network). This is a required pin in all integrations. Pin 24: /DTR1 Data Terminal Ready is used extensively to control modem operations as discussed in the Design Guide. This pin is not strictly required, although it is required for Windows ACPI. If DTR is not used in your integration, /DTR1 must be tied active (low) by connecting to ground.
Serial Interfaces The SB555 is also protected by this FET when the modem is powered down while the MCU remains powered up. The modem’s input pins should not have a voltage applied to them that is more than 0.3 V above VCC, which could otherwise happen when the modem is powered down. Pin 25: GND This is a signal ground made available in proximity to the other serial port pins for convenience.
SB555 Hardware Integration Guide Pin 28: /CTS1 Clear To Send is asserted by the modem when it is capable of receiving data from the host, and deasserted when the modem’s buffers are full (or the modem is not ready to receive commands from the host). This pin is also the final signal to the host indicating that the modem has completed its initialization and is ready for use. Only if the application can tolerate data loss due to transmission overruns, should this pin can be left unconnected.
Serial Interfaces the connection attempt is either answered or dropped. The other event triggers (SMS messages and return to coverage) will assert /RI1 three times for each triggering event. Your implementation must handle the detection of events and ignore any additional cycles that are not needed. Pin 30: GND This is a signal ground made available in proximity to the other serial port pins for convenience.
SB555 Hardware Integration Guide Sample 1: Internal host integration This sample integrates all signals of the serial port to an MCU. Buffers are used to manage the level conversions between 3.0 V at the modem and 3.3 V at the MCU. SN74AHC541 (or equivalent) octal buffers powered by a 3.0 V (VBUF) rail will serve on the inputs to the modem. Connect the /OE1 and /OE2 buffer pins to GND. Connect the inputs of any unused buffers to GND and leave the outputs unconnected.
Serial Interfaces This sample uses an open drain on /DTR1, which is discussed in the description of Pin 24: /DTR1 on page 42. If the host will be using partial system shutdown to conserve power—relying on the modem to wake up the host via the ring indicator—then the /RI pin at the MCU will have to be an interruptcapable input to trigger the host wakeup.
SB555 Hardware Integration Guide Figure 4-2: Primary serial port integration—external RS-232 connector Depending on the capabilities of the selected chip, the ring indicator may still be used to control host power. Provided the 3.0 V supply is active and the software switch is off, the chip may still pass the /RI1 signal to another pin (not shown) that can be used to wake the local host.
Serial Interfaces Sample 3: Minimum integration At a minimum, data receive (RxD1) and transmit (TxD1), and ground (GND) are required. This sample integration does not enforce flow control so data overruns and lost data are possible; your application must be tolerant of this. The minimum required integration is described in Table 4-3 and the block diagram in Figure 4-3: Table 4-3: Primary port minimum integration Signal Rev 1.0 Apr.
SB555 Hardware Integration Guide Figure 4-3: Primary serial port integration—minimum sample Note: The modem is not capable of ignoring RTS/ CTS flow control. If these signals are not used in your integration, then RTS must be forced active (low) when the modem is powered. The modem firmware always respects hardware handshaking. This means that if RTS/CTS are not used, the /RTS1 signal input to the modem must be forced active (low) by connecting it to ground.
Serial Interfaces Secondary port Note: This port is required for operation with Watcher, the Sierra Wireless enabling software. The secondary port of the SB555 embedded modem is used to exchange control and status information while a data connection is in progress on the primary port. The secondary port can also support CAIT—a diagnostics tool— used during CDG3 testing.
SB555 Hardware Integration Guide Pin 17: /CTS2 The Clear To Send signal is optional and can be left unconnected if not used. The modem will assert and deassert it regardless of the hardware integration. Clear To Send is asserted by the modem when it is capable of receiving CnS commands from the host, and deasserted when the modem’s buffer is full (or the modem is not ready to receive CnS commands from the host).
Serial Interfaces Pin 20: RxD2 This is the data channel from the modem to the host for CnS messages and notifications. This is a required pin in all integrations using Watcher; otherwise it is optional. Pin 25: GND This is a signal ground made available in proximity to the other serial port pins for convenience. Port configuration The secondary serial port is configured for 8-data bits, no parity bits, and 1-stop bit. The DTE host data-rate on the secondary serial port can be from 9600 bps to 115.
SB555 Hardware Integration Guide Secondary port sample integration Note: The secondary port is typically not extended to an outside RS-232 connector, although this can be done in a completely standalone modem product—one not using built-in host application software. This sample integrates all signals of the serial port to an MCU. Buffers are used to manage the level conversions between 3.0 V at the modem and 3.3 V at the MCU.
Serial Interfaces Minimum integration To use the port, the minimum integration is described in the following table: Table 4-5: Secondary port minimum integration Signal Pin Requirement /CTS2 17 Optional /RTS2 18 GND TxD2 19 Required RxD2 20 Required GND 25 Required Figure 4-5: Secondary serial port minimum integration At a minimum, receive (RxD2) and transmit (TxD2) data, along with ground (GND) are required.
SB555 Hardware Integration Guide 56 Proprietary and Confidential 2130075
5: Voice Interface • Introduction • Headset • Line level 5 Introduction to voice features The SB555 CDMA2000 1X embedded modem supports voice operation similar to a cellular telephone. Integration of the modem to use the voice features requires a microphone input and speaker output. These can be either directly to a standard cellular headset or to your custom audio circuit (at line level).
SB555 Hardware Integration Guide Figure 5-1: Simplified audio block diagram Setting line level (~AUDMOD) primarily affects the amount of microphone gain. There is also some associated filtering, used to compensate for the headset microphone, that will be switched out (flat response) when using the line level configuration. Calibration of the microphone and speaker levels is handled on the digital side of the Codec. Use of ~MICLVL and ~SPKLVL is described in the Configuration and Verification Guide.
Voice Interface Pinouts Table 5-1: Analog voice interface pinouts Pin Name Description Type Termination if not used 13 MIC+ Voice Mic+ Input (Diff.) AGND 14 SPKR+ Voice Speaker Output Not connected 15 MIC- Voice Mic- Input (Diff.) AGND 16 AGND Audio Common Ground (AGND) Not connected Note: The Audio Common Ground is independent of the system’s signal ground. If the audio circuitry is not used, the inputs (pins 13 and 15) should be connected to AGND (pin 16).
SB555 Hardware Integration Guide Headset integration This is the default configuration from the factory. Level calibration is described in the Verification and Configuration Guide (document #2130078). Headset interface specifications The modem’s analog voice interface configured for direct use with a standard cellular headset has the following electrical specifications: Table 5-2: Headset interface electrical characteristics Parameter Conditions Min Typ. Max 4.2 4.
Voice Interface Table 5-2: Headset interface electrical characteristics (cont.) Parameter Conditions IMIC Electret condenser Source = 1.8 VDC @ 2200 Ω Mic DC current Min Typ. 220 Max 500 Units µA Speaker Output Ω ZL Load impedance Single-ended PO Speaker output power 32Ω load digital input = +3 dBm0 @ 1020 Hz 8.
SB555 Hardware Integration Guide Microphone input (headset) The microphone input is a capacitively connected differential input, with input impedance greater than 4 kΩ. Microphone signals should be -44 dBV (18 mVp-p) nominal. Note: Single-ended drive will reduce input impedance by 50% to 2.1 kΩ typical. If a single-ended drive is desired, the MIC- input must be connected to the Audio Common ground (pin 16) as close to the microphone, or its connector, as possible.
Voice Interface 1 2 3 13 MIC+ 14 SPKR+ 15 MIC 16 AGND 4 SJ - 2504N Figure 5-2: Sample headset integration A preferred integration would use both MIC+ and MIC- as a differential pair (with ground on either side) to reduce noise. Note: This sample does not include ESD protection. You are responsible for all ESD protection circuitry. Line level voice integration The modem’s analog voice interface is configured at the factory for direct use with a standard cellular headset.
SB555 Hardware Integration Guide The interface has the following electrical specifications: Table 5-3: Line level interface electrical characteristics Parameter Conditions Min Typ. Max Units 4.2 4.5 kΩ 2.28 VP-P Line Input ZIN Input impedance Differential 4 VI Maximum input level MIC+ or MICsingle-ended 0dBm0 Reference level Amp Gain = -2 dB ∆AV Gain error -30 dBm0 to +3 dBm0 input -1.5 SINAD S:(THD+N) -45 dBm0 to +3 dBm0 input 25 1.14 0 VRMS +1.
Voice Interface Table 5-3: Line level interface electrical characteristics (cont.) Parameter Conditions Min Typ. Max Units ∆AV Gain error -30 dBm0 to +3 dBm0 input -1.5 0 +1.5 dB Receive noise Digital input = 0x0000 A-weighted SINAD S:(THD+N) -45 dBm0 to +3 dBm0 input 25 IMD Intermod.
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6: Control Signals • • • • Introduction Status indicators Shutdown control Reset 6 Introduction The SB555 embedded modem makes use of several control signals to indicate connection state, control the shutdown process, and reset the modem. This chapter deals with the hardware integration of these control interfaces: • Status outputs • Shutdown request and acknowledge • Reset Control interface specifications All signals are 3.0 V, HCMOS logic compatible.
SB555 Hardware Integration Guide Table 6-1: Control interface electrical characteristics (Continued) Parameter Conditions Min IIL Input current 0 V applied to input 0 VOH HI output IOH = 2.0 mA 2.4 VOL LO output IOL = -2.0 mA IOH Output current IOL Output current Typ. Max -120 Units µA 3.0 V 0.4 V VOH > 2.0 V 3.0 mA VOL < 1.0 V -3.
Control Signals ESD protection You are responsible for any ESD protection required. An appendix (page 95) provides background on ESD. Status indicators Four status output indicators are provided on the SB555 modem.
SB555 Hardware Integration Guide You can implement as few or as many of these signals as suits your project. See the Design Guide (document #2130179) for a discussion of the specific applications. Human interface (LEDs) By default from the factory, these outputs are defined for a human interface presuming connection to LED indicators (blinking patterns are used). All four signals are active low. They are capable of directly driving LEDs with up to 2 mA sinking or sourcing. Up to 3 mA is supported if 3.
Control Signals Figure 6-1: Sample LED integration The 3.0 V low-dropout (LDO) voltage regulator is used to provide the appropriate voltage for the LEDs. However, if the supply power (VBATT) never exceeds 3.30 V, or the LEDs provide sufficient voltage drop to prevent back-powering, this voltage regulator can be omitted; the LED resistors can be connected directly to VBATT. If the LEDs were connected directly to a VBATT of 4.2 V, the voltage at the /Status pins could exceed the limit of VCC + 0.
SB555 Hardware Integration Guide Machine interface To configure the modem to use the machine interface use one of these techniques: • AT command AT~SOMOD=1 • CnS command KST_SOMOD (5003) All four signals are active low. Depending on the application, there may be a need to trigger interrupts on falling or rising edges, or both. There is a “damping” applied to Status 3 and Status 4 (pins 9 and 11). When triggered active (on, low) they will remain on for a minimum of 50 ms.
Control Signals buffer powered by the MCU's 3.3 V VCC rail is suggested. Connect the /OE1 and /OE2 pins to GND. This buffer is there mainly to protect the host MCU if it is ever powered down while the SB555 remains powered up. Only omit this buffer if all MCU input pins can tolerate 3.0 V applied to them while the MCU is powered down (MCU VCC = 0 V) without back-powering the MCU, and if the MCU input pins don’t have pullups which could back-power the modem when it is powered down.
SB555 Hardware Integration Guide Buffers should be used to protect the modem from back-power, overpower, and to adjust for 3.0 V to 3.3 V logic differences. Pin 37: /Shdn_Ack Shutdown Acknowledge is asserted (low) by the modem when the shutdown process is complete and the modem may be reset or powered off. Use of a buffer is recommended for hosts not using 3.0 V logic. It is also required if the host cannot handle cases where the modem is active (the pin is deasserted high) while the host is powered down.
Control Signals Pin 39: /Reset The modem can be reset using a hardware control signal on pin 39, /Reset. The signal is active low and must be asserted for a minimum of 40 µs. The /Reset pin of the SB555 should be driven by an open drain device (for example, a TMOS FET such as the 2N7000 or 2N7002), with a pulldown resistor on the input gate of the FET.
SB555 Hardware Integration Guide Sample shutdown interface integration This sample shows the shutdown handshaking pins buffered to protect both the modem and the host MCU from back-power situations, and to handle logic level conversion. The manual on/off switch to the modem is shown for consistency with other samples but can be omitted. Figure 6-3: Sample shutdown and reset integration Buffers are used to manage the level conversions between 3.0 V at the modem and 3.3 V at a host MCU.
Control Signals powered by the MCU's 3.3 V VCC rail for the modem output, and powered by the modem’s 3.0 V VBUF for the modem input, are suggested. Connect the /OE1 and /OE2 pins to GND. The host in this sample has control of the power to the modem. Following assertion of /Shdn_Ack, the host can switch off the modem via the MOSFET. Shutdown sequence The suggested shutdown sequence is described below: 1. The user switches off the host using the soft on/off switch. 2.
SB555 Hardware Integration Guide shutdown request is issued. It the modem must disconnect a call or deregister from the network, more time is needed. Typical shutdown time, measured from the assertion of the request to the acknowledgement from the modem is given the table below. Table 6-4: Shutdown timing Modem activity Typical time to shutdown (seconds) Voice call connected 3.25 Data call connected 2.3 Registered but no call active (must contact the network to deregister) 2.
7: RF Integration • Introduction • RF connection • Antenna and cabling • Interference and sensitivity 7 Introduction This chapter covers issues related to the Radio Frequency (RF) integration of the SB555 embedded modem. The modem’s RF specifications are noted in the table below. Table 7-1: Radio specifications Transmitter power Maximum 224 mW into 50 Ω (+23.
SB555 Hardware Integration Guide RF connection The antenna connector is an MMCX connector jack oriented in line with the module longitudinal axis. Mating connectors can be either straight or right-angle plugs. The RF connector of the SB555 can be connected directly to test equipment. Connection to an antenna requires the antenna type to be correctly matched to the modem, using a 50 Ω cable.
RF Integration The module’s MMCX antenna connector is designed for high reliability (stiff detent) but few connection cycles (500 cycles). Depending on your application, this may not support end-user demands. You may need to consider presenting an alternate connector (SMA, SMB, TNC, etc.) to the user. Ground plane isolation Ground loops must be avoided between the host connector and the antenna. Figure 7-1: Ground plane RF Isolation Rev 1.0 Apr.
SB555 Hardware Integration Guide The coaxial cable connecting the module to the antenna carries the ground connection. There must be an electrical isolation between the ground plane at the antenna and the ground plane used by the modem. If these two ground planes were not isolated, there would be a ground loop from the modem through the coaxial cable and back through the ground plane to the modem’s own ground. This must be avoided.
RF Integration Antenna and cabling After determining the connection method (integral or user-accessible connector) the selection of an antenna and cable must be made. Matching antenna and cable Matching the antenna gain with cable loss is critical to effective RF performance. For proper matching, the antenna should be 50 ohms with a return loss |Γ| ≤ -10 dB between 824 – 894 MHz and 1850 – 1990 MHz. Overall system antenna gain, with cable loss, should be ≥ -2 dBi and ≤ +2 dBi.
SB555 Hardware Integration Guide most applications, but this does not mean that you can ignore antenna placement. See “Interference and sensitivity” on page 84. Cables All connecting cables between the modem and the antenna must be 50 Ω. Mismatching the impedance will result in a significant reduction in RF performance. Interference and sensitivity There are several sources of interference that could impact the SB555 modem’s RF performance.
RF Integration Device generated RF All electronic computing devices generate radio frequency (RF) interference. You should pay particular attention to RF noise as it can impact the sensitivity of the SB555 modem’s radio receiver. The proximity of the host’s electronics to the antenna and radio have an effect on the radio sensitivity. There are many high-speed devices (in particular the processor itself) running at frequencies of 10’s of MHz.
SB555 Hardware Integration Guide interference may be reduced. The drawback of this approach is that the modem may be less convenient to use. • Shield the host device. The SB555 itself is well shielded to avoid interference, however it is not practical to shield the antenna for obvious reasons. It may be practical to employ shielding over the worst radiating elements of the host device (e.g. the main processor) to reduce the emissions.
RF Integration The SB555 radio circuits use a number of Intermediate Frequency (IF) stages. The following specific frequencies should be avoided or suppressed in the host device to maintain the best sensitivity performance: • 183.6 MHz • 228.6 MHz • 263.6 MHz Modem generated RF switching noise In addition to outside frequencies interfering with the modem’s sensitivity, the modem itself can cause noise in hearing aids due to the keying of the transmitter.
SB555 Hardware Integration Guide 75%. The duty cycle may hit the maximum 75% during large file transfers when the system has allocated the maximum bandwidth to the user. Otherwise, the duty cycle will be lower. Power per transmission is infinitely variable over a 73.5 dB range from -50 dBm to +23.5 dBm. Power varies up or down over this range during the transmission and is adjusted every 1.25 ms.
A Appendix A: Host Connector Pinouts The following table lists the pinouts of the 40-pin host connector of the SB555 embedded modem. Those pins shown as Reserved are to be terminated as noted in the rightmost column. Signal type indicates if the signal is an input to the modem or output from the modem. The column marked “U/D drv” indicates any modem internal pullup or pulldown resistor on inputs, or the drive capability in mA for outputs.
SB555 Hardware Integration Guide Table 7-2: Host connector pinouts (cont.) Pin 90 Name Description Signal type U/D drv Termination if not used 13 MIC+ Voice Mic+ Input (Diff.) U AGND 14 SPKR+ Voice Speaker Output -- Not connected 15 MIC- Voice Mic- Input (Diff.
Appendix A: Host Connector Pinouts Table 7-2: Host connector pinouts (cont.) Pin Name Description Signal type U/D drv Termination if not used 33 Reserved Input D Ground 34 Reserved Output 3 Not connected 35 Reserved -- Not connected 36 Reserved -- Not connected 37 /Shdn_Ack Shutdown Acknowledge Output 2 Not connected 38 /ShutDown Shutdown Request Input D 3.0 V 39 /Reset Reset Input U 3.0 V 40 Reserved -- Not connected Rev 1.0 Apr.
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Appendix B: Sample Integration Rev 1.0 Apr.
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Appendix C: Electrostatic Discharge • • • • • Introduction Creation Damage Protection Considerations C Introduction ESD (Electrostatic Discharge) is commonly experienced as the static shock that might occur when reaching for a door handle. It is caused by a difference in electrical potential between you and the door handle, and can be in excess of 3500 volts. Such a sudden discharge of high voltage can cause severe damage to electronic circuits and must be protected against.
SB555 Hardware Integration Guide volts. When two objects of different potential get close enough, an electrostatic discharge takes place. The movement of an electronic device in and out of a persons pocket or a carrying case can cause a charge to develop. When the charged object encounters another object with a sufficient difference in potential (like a person’s finger), there will be a discharge to equalize the charges in the two objects.
Appendix C: Electrostatic Discharge the device may still appear to function normally in most respects, but display abnormal behavior in certain circumstances. Quite often there is no observed spark involved in the discharge. The user of a device may not be aware that there was a damaging discharge. Types of damage The damage resulting from ESD can take one of three forms: Fatal The device is permanently damaged due to junction shorting, oxide punch-through, or melting.
SB555 Hardware Integration Guide Protection from ESD There are several types of suppression devices on the market. Many are specifically designed to provide ESD protection. Requirements Any ESD protection must limit the voltage reaching the device to a non-destructive level. This may be above the normal operating voltage of the device. It must also respond extremely quickly to an event. The discharge happens very rapidly.
Appendix C: Electrostatic Discharge voltage exceeds the nominal voltage of the device. This diverts the energy away from the protected circuit, limiting it to the clamping voltage of the TVS diode. After the high-voltage event passes, the TVS diode returns to its highimpedance state. Zin External Interface ESD Current TVS Diode Protected Circuit Figure 7-3: Simple TVS diode protection The TVS diode should be rated at the level of ESD protection desired.
SB555 Hardware Integration Guide Volts ESD Pulse Overshoot Failure Voltage Clamp Voltage Vcc Time Figure 7-4: Possible inductance voltage overshoot The voltage developed across an inducted load is proportional to the rate of change in the current (V = L di/dt). The rise time of ESD events is typically very fast, in the order of 1 ns to reach its peak. Making the shunt paths as short as possible reduces the effects of parasitic inductance.
Appendix C: Electrostatic Discharge Routing critical signals near the edge of a board or near protected lines can increase the risk of inducing damage.
SB555 Hardware Integration Guide Capacitance Generally, the lower the clamping voltage of the TVS diode, the higher the capacitance. This extra capacitance might attenuate signals in highspeed digital circuitry. Selecting the right protection device also involves protecting the functionality of the circuit. This problem is even more apparent with the RF antenna interface, where attenuation can be costly. Care must be taken to keep insertion loss low while maintaining adequate protection.
Appendix C: Electrostatic Discharge Selection guidelines The parameters related to protection specifications you need to consider are: Reverse Standoff Voltage (VRWM) The normal operating voltage of the device. At this voltage, the protection device will appear as high impedance to the modem. Reverse Breakdown Voltage (VBR) This is the voltage at which the protection device begins to conduct and becomes the low impedance path.
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