Datasheet

ManualsBrandsNXP SEMICONDUCTORS ManualsSensorsTemperature sensor SMD

1. General description

The LM75A is a temperature-to-digital converter using an on-chip band gap temperature

sensor and Sigma-delta A-to-D conversion technique. The device is also a thermal

detector providing an overtemperature detection output. The LM75A contains a number of

data registers: Conﬁguration register (Conf) to store the device settings such as device

operation mode, OS operation mode, OS polarity and OS fault queue as described in

Section 7 “Functional description”; temperature register (Temp) to store the digital temp

reading, and set-point registers (Tos and Thyst) to store programmable overtemperature

shutdown and hysteresis limits, that can be communicated by a controller via the 2-wire

serial I

C-bus interface. The device also includes an open-drain output (OS) which

becomes active when the temperature exceeds the programmed limits. There are three

selectable logic address pins so that eight devices can be connected on the same bus

without address conﬂict.

The LM75A can be conﬁgured for different operation conditions. It can be set in normal

mode to periodically monitor the ambient temperature, or in shutdown mode to minimize

power consumption. The OS output operates in either of two selectable modes:

OS comparator mode or OS interrupt mode. Its active state can be selected as either

HIGH or LOW. The fault queue that deﬁnes the number of consecutive faults in order to

activate the OS output is programmable as well as the set-point limits.

The temperature register always stores an 11-bit 2's complement data giving a

temperature resolution of 0.125 °C. This high temperature resolution is particularly useful

in applications of measuring precisely the thermal drift or runaway.

The device is powered-up in normal operation mode with the OS in comparator mode,

temperature threshold of 80 °C and hysteresis of 75 °C, so that it can be used as a

stand-alone thermostat with those pre-deﬁned temperature set points.

2. Features

n Pin-for-pin replacement for industry standard LM75 and offers improved temperature

resolution of 0.125 °C and speciﬁcation of a single part over power supply range from

2.8 V to 5.5 V

n Small 8-pin package types: SO8 and TSSOP8

n I

C-bus interface with up to 8 devices on the same bus

n Power supply range from 2.8 V to 5.5 V

n Temperatures range from −55 °C to +125 °C

n 11-bit ADC that offers a temperature resolution of 0.125 °C

LM75A

Digital temperature sensor and thermal watchdog

Rev. 04 — 10 July 2007 Product data sheet

Summary of content (24 pages)

PAGE 1
LM75A Digital temperature sensor and thermal watchdog Rev. 04 — 10 July 2007 Product data sheet 1. General description The LM75A is a temperature-to-digital converter using an on-chip band gap temperature sensor and Sigma-delta A-to-D conversion technique. The device is also a thermal detector providing an overtemperature detection output.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog n Temperature accuracy of: u ±2 °C from −25 °C to +100 °C u ±3 °C from −55 °C to +125 °C n Programmable temperature threshold and hysteresis set points n Supply current of 3.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog 5. Block diagram VCC LM75A BIAS REFERENCE POINTER REGISTER CONFIGURATION REGISTER BAND GAP TEMP SENSOR COUNTER TEMPERATURE REGISTER TIMER TOS REGISTER COMPARATOR/ INTERRUPT THYST REGISTER 11-BIT SIGMA-DELTA A-to-D CONVERTER OSCILLATOR POWER-ON RESET OS LOGIC CONTROL AND INTERFACE 002aad029 A2 A1 A0 SCL SDA GND Fig 1. Block diagram 6. Pinning information 6.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog Table 3. Pin description …continued Symbol Pin Description A1 6 Digital input. User-defined address bit 1. A0 7 Digital input. User-defined address bit 0. VCC 8 Power supply. 7. Functional description 7.1 General operation The LM75A uses the on-chip band gap sensor to measure the device temperature with the resolution of 0.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog In both cases, comparator mode and interrupt mode, the OS output is activated only if a number of consecutive faults, defined by the device fault queue, has been met. The fault queue is programmable and stored in the two bits, B3 and B4, of the Configuration register. Also, the OS output active state is selectable as HIGH or LOW by setting accordingly the configuration register bit B2.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog 8 devices can be connected to the same bus without address conflict. Because the input pins, SCL, SDA and A2 to A0, are not internally biased, it is important that they should not be left floating in any application. Table 4. Address table 1 = HIGH; 0 = LOW. MSB LSB 1 0 0 1 A2 A1 A0 7.4 Register list The LM75A contains four data registers beside the pointer register as listed in Table 5.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog read a register that is different from the one that has been recently read, the pointer byte must be included. However, a write to the LM75A must always include the pointer byte in the statement. The bus communication protocols are described in Section 7.10. At power-up, the Pointer value is equal to 0 and the Temp register is selected; users can then read the Temp data without specifying the pointer byte. 7.4.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog When reading register Temp, all 16 bits of the two data bytes (MSByte and LSByte) are provided to the bus and must be all collected by the controller to complete the bus operation. However, only the 11 most significant bits should be used, and the 5 least significant bits of the LSByte are zero and should be ignored. One of the ways to calculate the Temp value in °C from the 11-bit Temp data is: 1.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog Table 11. Tos register MSByte LSByte 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 D8 D7 D6 D5 D4 D3 D2 D1 D0 X X X X X X X Table 12. Thyst register MSByte LSByte 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 D8 D7 D6 D5 D4 D3 D2 D1 D0 X X X X X X X When a set-point register is read, all 16 bits are provided to the bus and must be collected by the controller to complete the bus operation.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog The main difference between the two modes is that in OS comparator mode, the OS output becomes active when Temp has exceeded Tos and reset when Temp has dropped below Thyst, reading a register or putting the device into shutdown mode does not change the state of the OS output; while in OS interrupt mode, once it has been activated either by exceeding Tos or dropping below Thyst, the OS output will remain active indefinitely until re
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog When the power supply voltage is dropped below the device power-on reset level of approximately 1.9 V (POR) and then rises up again, the device will be reset to its default condition as listed above. 7.10 Protocols for writing and reading the registers The communication between the host and the LM75A must strictly follow the rules as defined by the I2C-bus management.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog 1 2 3 4 1 0 0 1 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 0 0 0 0 0 0 0 1 A 0 0 0 4 5 6 7 8 9 SCL SDA S A2 A1 A0 W A device address START pointer byte write D4 D3 D2 D1 D0 A configuration data byte device acknowledge device acknowledge P device acknowledge STOP 001aad624 Fig 5.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 SCL (next) SDA S 1 0 0 1 A2 A1 A0 W A 0 0 0 device address 0 0 device acknowledge 3 4 P0 (next) A device acknowledge write 2 P1 pointer byte START 1 0 5 6 7 8 9 1 2 3 4 5 6 7 8 9 SCL (cont.) SDA (cont.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog 8. Application design-in information power supply 0.1 µF BUS 10 kΩ PULL-UP RESISTORS 10 kΩ SCL I2C-BUS SDA A2 DIGITAL LOGIC 10 kΩ VCC A1 A0 8 2 1 LM75A 3 OS DETECTOR OR INTERRUPT LINE 5 6 7 4 GND 002aad030 Fig 11. Typical application 9. Limiting values Table 15. Limiting values In accordance with the Absolute Maximum Rating System (IEC 60134). Symbol Parameter VCC Conditions Min Max Unit supply voltage −0.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog 11. Static characteristics Table 17. Static characteristics VCC = 2.8 V to 5.5 V; Tamb = −55 °C to +125 °C; unless otherwise specified. Symbol Parameter Conditions Min Typ[1] Max Unit TACC temperature accuracy Tamb = −25 °C to +100 °C −2 - +2 °C Tamb = −55 °C to +125 °C −3 - +3 °C Tres temperature resolution 11-bit digital temp data - 0.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog 12. Dynamic characteristics Table 18. I2C-bus interface dynamic characteristics[1] VCC = 2.8 V to 5.5 V; Tamb = −55 °C to +125 °C; unless otherwise specified. Symbol Parameter Conditions Min Typ Max Unit TCLK SCL clock period see Figure 12 2.5 - - µs tHIGH HIGH period of the SCL clock 0.6 - - µs tLOW LOW period of the SCL clock 1.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog 13. Package outline SO8: plastic small outline package; 8 leads; body width 3.9 mm SOT96-1 D E A X c y HE v M A Z 5 8 Q A2 A (A 3) A1 pin 1 index θ Lp 1 L 4 e detail X w M bp 0 2.5 5 mm scale DIMENSIONS (inch dimensions are derived from the original mm dimensions) UNIT A max. A1 A2 A3 bp c D (1) E (2) e HE L Lp Q v w y Z (1) mm 1.75 0.25 0.10 1.45 1.25 0.25 0.49 0.36 0.25 0.19 5.0 4.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog TSSOP8: plastic thin shrink small outline package; 8 leads; body width 3 mm D E SOT505-1 A X c y HE v M A Z 5 8 A2 pin 1 index (A3) A1 A θ Lp L 1 4 detail X e w M bp 0 2.5 5 mm scale DIMENSIONS (mm are the original dimensions) UNIT A max. A1 A2 A3 bp c D(1) E(2) e HE L Lp v w y Z(1) θ mm 1.1 0.15 0.05 0.95 0.80 0.25 0.45 0.25 0.28 0.15 3.1 2.9 3.1 2.9 0.65 5.1 4.7 0.94 0.7 0.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog 14. Soldering This text provides a very brief insight into a complex technology. A more in-depth account of soldering ICs can be found in Application Note AN10365 “Surface mount reflow soldering description”. 14.1 Introduction to soldering Soldering is one of the most common methods through which packages are attached to Printed Circuit Boards (PCBs), to form electrical circuits.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog 14.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog maximum peak temperature = MSL limit, damage level temperature minimum peak temperature = minimum soldering temperature peak temperature time 001aac844 MSL: Moisture Sensitivity Level Fig 15. Temperature profiles for large and small components For further information on temperature profiles, refer to Application Note AN10365 “Surface mount reflow soldering description”. 15. Abbreviations Table 21.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog 16. Revision history Table 22. Revision history Document ID Release date Data sheet status Change notice Supersedes LM75A_4 20070710 Product data sheet - LM75A_3 Modifications: • The format of this data sheet has been redesigned to comply with the new identity guidelines of NXP Semiconductors. • • • • Legal texts have been adapted to the new company name where appropriate. added (new) Section 4.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog 17. Legal information 17.1 Data sheet status Document status[1][2] Product status[3] Definition Objective [short] data sheet Development This document contains data from the objective specification for product development. Preliminary [short] data sheet Qualification This document contains data from the preliminary specification. Product [short] data sheet Production This document contains the product specification.
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LM75A NXP Semiconductors Digital temperature sensor and thermal watchdog 19. Contents 1 2 3 4 4.1 5 6 6.1 6.2 7 7.1 7.2 7.3 7.4 7.4.1 7.4.2 7.4.3 7.4.4 7.5 7.6 7.7 7.8 7.9 7.10 8 9 10 11 12 13 14 14.1 14.2 14.3 14.4 15 16 17 17.1 17.2 17.3 17.4 18 General description . . . . . . . . . . . . . . . . . . . . . . 1 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Ordering information . . . . . . . . . . . . . . .