Datasheet

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_______________General Description

The MAX3320 combines a microprocessor (µP) super-

visory circuit with an RS-232 transceiver. The power-on

reset performs a single function: it asserts a reset signal

whenever the V

supply voltage declines below a pre-

set threshold, staying asserted for at least 100ms after

rises above the reset threshold. The MAX3320 has

an active-low RESET output, which is guaranteed to be in

the correct state for V

down to 1V. The reset compara-

tor is designed to ignore fast transients on V

. Reset

thresholds suitable for operation with a variety of supply

voltages are available.

The MAX3320 transceivers have a proprietary low-

dropout transmitter output stage, enabling true RS-232

performance with a dual charge pump powered from a

+3V to +5.5V supply. The device requires only four

small 0.1µF external charge-pump capacitors, and is

guaranteed to run at data rates of up to 250kbps. It

comes in the space-saving 20-pin SSOP package.

________________________Applications

Palmtop Computers

Portable/Battery-Powered Equipment

Hand-Held Equipment

Peripherals

Printers

____________________________Features

♦ Precise Monitoring of 5V and 3.3V Power-

Supply Voltages:

— 100ms (min) Power-On

RESET Pulse Width

— Power-Supply Transient Immunity

— Guaranteed RESET Valid to V

= 1V

♦ 4µA Supply Current Achieved with

AutoShutdown Plus

♦ Receivers Always Active

♦ Power-On Reset Always Active

♦ 4µA Low-Power Shutdown

♦ 250kbps Guaranteed Data Rate

MAX3320A/B/L/T

3V to 5.5V, up to 250kbps True RS-232 Transceiver

with 4µA AutoShutdown Plus and Power-On Reset

________________________________________________________________

Maxim Integrated Products

C1+

C1-

GNDV-

C2-

C2+

V+

TOP VIEW

T1OUT

T2OUT

R1IN

R2INR2OUT

R1OUT

T2IN

T1IN

FORCEON

FORCEOFFRESET

INVALID

MAXxxx

SSOP

MAX3320

__________________Pin Configuration

19-1253; Rev 0; 8/97

PART*

MAX3320_CAP

MAX3320_EAP -40°C to +85°C

0°C to +70°C

TEMP. RANGE PIN-PACKAGE

20 SSOP

______________Ordering Information

This part offers a choice of reset threshold voltage. From the

table below, select the suffix corresponding to the desired

threshold and insert it into the blank to complete the part

number.

AutoShutdown Plus is a trademark of Maxim Integrated Products.

SUFFIX

RESET THRESHOLD

(V)

4.25

2.85

L 4.63

T 3.08

Typical Operating Circuit appears at end of data sheet.

For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.

For small orders, phone 408-737-7600 ext. 3468.

Summary of content (12 pages)

PAGE 1
9-1253; Rev 0; 8/97 3V to 5.5V, up to 250kbps True RS-232 Transceiver with 4µA AutoShutdown Plus and Power-On Reset The MAX3320 transceivers have a proprietary lowdropout transmitter output stage, enabling true RS-232 performance with a dual charge pump powered from a +3V to +5.5V supply. The device requires only four small 0.1µF external charge-pump capacitors, and is guaranteed to run at data rates of up to 250kbps. It comes in the space-saving 20-pin SSOP package.
PAGE 2
MAX3320A/B/L/T 3V to 5.5V, up to 250kbps True RS-232 Transceiver with 4µA AutoShutdown Plus and Power-On Reset ABSOLUTE MAXIMUM RATINGS Short-Circuit Duration VCC .............................................................................-0.3V to 6V T_OUT....................................................................Continuous V+ (Note 1) .................................................................-0.3V to 7V Continuous Power Dissipation (TA = +70°C) V- (Note 1).................................
PAGE 3
V to 5.5V, up to 250kbps True RS-232 Transceiver with 4µA AutoShutdown Plus and Power-On Reset (VCC = 3V to 5.5V, C1–C4 = 0.1µF (tested at 3.3V ±10%), C1 = 0.047µF, C2–C4 = 0.33µF (tested at 5V ±10%), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS MIN TYP MAX UNITS INVALID Output Voltage High IOUT = -1mA Receiver Positive or Negative Threshold to INVALID High Figure 3 0.
PAGE 4
TIMING CHARACTERISTICS (VCC = 3V to 5.5V, C1–C4 = 0.1µF, C1–C4 = 0.1µF (for 3.3V ±10%), C1 = 0.047µF, C2–C4 = 0.33µF (tested at 5V ±10%), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) Maximum Data Rate PARAMETER CONDITIONS RL = 3kΩ, CL = 1000pF, one transmitter switching Receiver Propagation Delay R_IN to R_OUT, CL = 150pF Transmitter Skew | tPHL - tPLH | | tPHL - tPLH | Receiver Skew MIN TYP 0.3 tPLH 0.
PAGE 5
3V to 5.5V, up to 250kbps True RS-232 Transceiver with 4µA AutoShutdown Plus and Power-On Reset (VCC = 3.3V, 250kbps data rate, C1–C4 = 0.1µF, all transmitters loaded with 3kΩ. Typical values are at TA = +25°C, unless otherwise noted.) NORMALIZED POWER-UP RESET DELAY vs. TEMPERATURE MAXIMUM TRANSIENT DURATION vs. RESET COMPARATOR OVERDRIVE SHUTDOWN MODE 200 150 100 NOT IN SHUTDOWN MODE 50 1.030 POWER-UP RESET DELAY 250 MAX3320 TOC06 1.040 MAX3320toc05 MAXIMUM TRANSIENT DURATION (µs) 300 1.020 1.
PAGE 6
MAX3320A/B/L/T 3V to 5.5V, up to 250kbps True RS-232 Transceiver with 4µA AutoShutdown Plus and Power-On Reset Table 1.
PAGE 7
3V to 5.5V, up to 250kbps True RS-232 Transceiver with 4µA AutoShutdown Plus and Power-On Reset Tables 1 and 2 and Figure 2 summarize the MAX3320’s operating modes. FORCEON and FORCEOFF override the automatic circuitry and force the transceiver into its normal operating state or into its low-power standby state. When neither control is asserted, the IC enters AutoShutdown Plus mode and selects between these states automatically, based on the last receiver or transmitter input edge received.
PAGE 8
MAX3320A/B/L/T 3V to 5.5V, up to 250kbps True RS-232 Transceiver with 4µA AutoShutdown Plus and Power-On Reset INVALID REGION * RECEIVER INPUTS VOLTAGE ** TRANSMITTER INPUTS VOLTAGE TRANSMITTER OUTPUTS VOLTAGE INVALID OUTPUT VCC 0 tAUTOSHDN INVL tAUTOSHDN tWU tWU V+ VCC 0 V* ALL RECEIVER/TRANSMITTER INPUTS INACTIVE ** ANY ONE RECEIVER/TRANSMITTER INPUT BECOMES ACTIVE FORCEON = GND, FORCEOFF = VCC Figure 3a. AutoShutdown Plus and INVALID Timing Diagram INVALID HIGH RECEIVER INPUT LEVELS 2.
PAGE 9
3V to 5.5V, up to 250kbps True RS-232 Transceiver with 4µA AutoShutdown Plus and Power-On Reset MAX3320A/B/L/T FORCEON = FORCEOFF VCC 2V/div T2OUT MAX3320 VCC GND RESET 2V/div 100k T1OUT VCC = 3.3V C1 - C4 = 0.1µF Figure 4. Ensuring RESET Valid to VCC = 0V When using the minimum required capacitor values, make sure the capacitor value does not degrade excessively with temperatures outside the 0°C to +70°C range. If in doubt, use capacitors with a larger nominal value.
PAGE 10
MAX3320A/B/L/T 3V to 5.5V, up to 250kbps True RS-232 Transceiver with 4µA AutoShutdown Plus and Power-On Reset 5V 0V T1IN 5V 0V T1IN 5V T1OUT R1IN 0V 5V T1OUT R1IN 0V -5V 5V 0V R1OUT -5V 5V 0V R1OUT 2µs/div 2µs/div VCC = 3.3V C1 - C4 = 0.1µF CLOAD = 1000pF VCC = 3.3V C1 - C4 = 0.1µF CLOAD = 1000pF Figure 7. Loop-Back Test Result at 120kbps Table 4. Logic-Family Compatibility with Various Supply Voltages SYSTEM POWER-SUPPLY VOLTAGE (V) VCC SUPPLY VOLTAGE (V) COMPATIBILITY 3.3 3.
PAGE 11
3V to 5.5V, up to 250kbps True RS-232 Transceiver with 4µA AutoShutdown Plus and Power-On Reset +3.3V VCC 0.1µF C1 0.1µF VCC C1+ V+ C3* 0.1µF C1- C2 0.1µF C2+ MAX3320 VC4 0.1µF C2VCC T1IN T1 T2IN T2 T1OUT T2OUT RS-232 OUTPUTS FORCEOFF FORCEON µP SYSTEM R1OUT AUTOSHUTDOWN PLUS R1IN R1 5k R2OUT RESET INPUT R2IN R2 5k RESET INVALID RS-232 INPUTS GND *C3 MAY BE RETURNED TO EITHER VCC OR GND.
PAGE 12
________________________________________________________Package Information SSOP.EPS MAX3320A/B/L/T 3V to 5.5V, up to 250kbps True RS-232 Transceiver with 4µA AutoShutdown Plus and Power-On Reset Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.