MAX3380EEUP+T - Maxim Integrated

General Description

The MAX3380E/MAX3381E are +2.35V to +5.5V-pow-

ered EIA/TIA-232 and V.28/V.24 communication inter-

faces with low power requirements, high data-rate

capabilities, and enhanced electrostatic discharge

(ESD) protection on both the TTL and RS-232 sides.

The MAX3380E/MAX3381E have two receivers and two

transmitters. All RS-232 inputs, outputs, and logic input

pins are protected to ±15kV using IEC 1000-4-2 Air-

Gap Discharge method and the Human Body Model,

and ±8kV using IEC 1000-4-2 Contact Discharge

method.

The proprietary low-dropout transmitter output stage

enables true RS-232 performance from a +3.1V to

+5.5V supply with a dual charge pump. The parts

reduce the transmitter output levels to RS-232-compati-

ble levels with no increase in supply current for sup-

plies less than +3.1V and greater than +2.35V. The

+2.35V to +5.5V operating range is fully compatible

with lithium-ion (Li+) batteries. The charge pump

requires only four small 0.1µF capacitors for operation.

The MAX3380E/MAX3381E transceivers use Maxim’s

revolutionary AutoShutdown Plus™ feature to auto-

matically enter a 1µA shutdown mode. These

devices shut down the on-board power supply and

drivers when they do not sense a valid signal transi-

tion for 30 seconds on either the receiver or trans-

mitter inputs.

The MAX3380E is capable of transmitting data at

rates of 460kbps while maintaining RS-232 output

levels, and the MAX3381E operates at data rates up

to 250kbps. The MAX3381E offers a slower slew rate

for applications where noise and EMI are issues. The

MAX3380E/MAX3381E have a unique VLpin that

allows interoperation in mixed-logic voltage systems

down to +1.65V. Both input and output logic levels

are referenced to the VLpin. The MAX3380E/MAX3381E

are available in a space-saving TSSOP package.

Applications

Cell Phone Data Lump Cables

PDA Data Lump Cables

GPS Receivers

Digital Cameras

Features

♦±15kV ESD Protection on All CMOS and RS-232

Inputs and Outputs (Except INVALID)

±15kV Human Body Model

±15kV IEC 1000-4-2 Air-Gap Discharge

±8kV IEC 1000-4-2 Contact Discharge

♦Operates Over Entire Li+ Battery Range

♦Low Logic Threshold Down to +1.65V for

Compatibility with Cell Phone Logic Supply Voltages

♦1µA Low-Power AutoShutdown Plus Mode

♦Compatible with Next-Generation GSM Data Rates

♦20-Pin TSSOP Package

MAX3380E/MAX3381E

+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers

with ±15kV ESD-Protected I/O and Logic Pins

________________________________________________________________ Maxim Integrated Products 1

19-2128; Rev 0; 8/01

Ordering Information

PART TEMP. RANGE

PIN-PACKAGE

MAX3380ECUP

0°C to +70°C

20 TSSOP

MAX3380EEUP

-40°C to +85°C

20 TSSOP

MAX3381ECUP

0°C to +70°C

20 TSSOP

MAX3381EEUP

-40°C to +85°C

20 TSSOP

Pin Configuration appears at end of data sheet.

MAX3380E/

MAX3381E

R2OUT

R1OUT

R2IN

GND

RS-232

OUTPUTS

TTL/CMOS

INPUTS T2IN

T1IN

C2-

C2+

C1-

C1+

R1IN

T2OUT

T1OUT

V-

V+

VCC VL

0.1μF

+3.3V

RS-232

INPUTS

TTL/CMOS

OUTPUTS

5kΩ

0.1μF

FORCEON

FORCEOFF

Typical Operating Circuit

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

AutoShutdown Plus is a trademark of Maxim Integrated Products

MAX3380E/MAX3381E

+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers

with ±15kV ESD-Protected I/O and Logic Pins

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC = +2.35V to +5.5V, VL= +1.65V to +5.5V. When VCC < +4.5V, C1 = C2 = C3 = C4 = 0.1µF; when VCC ≥+4.5V, C1 = 0.047µF,

C2 = C3 = C4 = 0.33µF; TA= TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL= +3.3V, TA= +25°C.)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional

operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to

absolute maximum rating conditions for extended periods may affect device reliability.

Note 1: V+ and V- can have maximum magnitudes of +7V, but their absolute difference cannot exceed +13V.

VCC to GND...........................................................-0.3V to +6.0V

VLto GND..............................................................-0.3V to +6.0V

V+ to GND .............................................................-0.3V to +7.0V

V- to GND ..............................................................+0.3V to -7.0V

V+ + |V-| (Note 1) .................................................................+13V

Input Voltages

T_IN, FORCEON, FORCEOFF to GND ...............-0.3V to +6.0V

R_IN to GND .....................................................................±25V

Output Voltages

T_OUT to GND...............................................................±13.2V

R_OUT, INVALID to GND...........................-0.3V to (VL+ 0.3V)

Short-Circuit Duration T_OUT to GND........................Continuous

Continuous Power Dissipation (TA= +70°C)

20-Pin TSSOP (derate 10.9mW/°C over +70°C) .........879mW

Operating Temperature Ranges

MAX3380ECUP/MAX3381ECUP........................0°C to +70°C

MAX3380EEUP/MAX3381EEUP .....................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

Receivers idle, VT_IN = VCC or GND,

FORCEON = GND, FORCEOFF = VCC 10

Supply Current, AutoShutdown

Plus ICC

FORCEOFF = GND 1 10

µA

Supply Current, Normal Operation

ICC FORCEON = FORCEOFF = VL, no load 0.3 1

LOGIC INPUTS (T_IN, FORCEON, FORCEOFF)

VCC = +5.5V, VL = +5.5V 0.4 1.2

Input Logic Threshold Low VIL VCC = +2.5V, VL = +1.65V 0.4 V

VCC = +5.5V, VL = +5.5V

VL ✕ 0.66

Input Logic Threshold High VIH VCC = +2.5V, VL = +1.65V

VL ✕ 0.66

Transmitter Input Hysteresis 0.5 V

Input Leakage Current

±0.01

±1µA

RECEIVER OUTPUTS (R_OUT) AND INVALID

Output Voltage Low IOUT = 500µA 0.5 V

Output Voltage High IOUT = -500µA

VL - 0.4 VL - 0.2

RECEIVER INPUTS (R_IN)

Input Voltage Range -25

+25

VL = +3.3V 0.6 1.2

Input Threshold Low TA = +25°CVL = +5.0V 0.8 1.5 V

VL = +3.3V 1.5 2.4

Input Threshold High TA = +25°CVL = +5.0V 1.8 2.4 V

Input Hysteresis 0.3 V

Input Resistance TA = +25°C 3 5 7 kΩ

MAX3380E/MAX3381E

+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers

with ±15kV ESD-Protected I/O and Logic Pins

_______________________________________________________________________________________ 3

PARAMETER

SYMBOL

CONDITIONS MIN

TYP MAX

UNITS

AutoShutdown Plus (FORCEON = GND, FORCEOFF = VL)

Positive threshold 2.7

Receiver Input Threshold to

INVALID Output High Figure 3 Negative threshold

-2.7

Receiver Input Threshold to

INVALID Output Low Figure 3

-0.3

0.3 V

Receiver Positive or Negative

Threshold to INVALID High tINVL VCC = +5.0V, Figure 4 0.3 µs

Receiver Positive or Negative

Threshold to INVALID Low tINVH VCC = +5.0V, Figure 4 30 µs

Receiver or Transmitter Edge to

Transmitters Enabled tWU VCC = +5.0V, Figure 4 15 µs

Receiver or Transmitter Edge to

Transmitters Shutdown

tAU T OS H D N

VCC = +5.0V, Figure 4 30 s

TRANSMITTER OUTPUTS

VCC Mode Switch Point

(VCC Falling) T_OUT = ±5.0V to ±3.7V

2.95

3.1

3.25

VCC Mode Switch Point

(VCC Rising) T_OUT = ±3.7V to ±5.5V 3.3 3.5 3.7 V

VCC Mode Switch Point

Hysteresis

400

C C

= + 3.25V to + 5.5V ,

C C

fal l i ng ±5

±5.4

Output Voltage Swing

All transmitter

outputs loaded

with 3kΩ to ground

C C

= + 2.5V to + 2.95V ,

C C

fal l i ng

±3.7

Output Resistance VCC = 0, transmitter output = ±2.0V

300 10M

Output Short-Circuit Current ±60

Output Leakage Current VOUT = ±12V, transmitters disabled ±25 µA

ESD PROTECTION

Human Body Model

±15

IEC 1000-4-2 Air-Gap Discharge Method

±15

R_IN, T_OUT, R_OUT, T_IN,

FORCEON, FORCEOFF

IEC 1000-4-2 Contact Discharge Method ±8

ELECTRICAL CHARACTERISTICS (continued)

(VCC = +2.35V to +5.5V, VL= +1.65V to +5.5V. When VCC < +4.5V, C1 = C2 = C3 = C4 = 0.1µF; when VCC ≥+4.5V, C1 = 0.047µF,

C2 = C3 = C4 = 0.33µF; TA= TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL= +3.3V, TA= +25°C.)

-6

-2

-4

0 1000 1500500 2000 2500 3000

TRANSMITTER OUTPUT VOLTAGE

vs. LOAD CAPACITANCE

MAX3380E toc01

LOAD CAPACITANCE (pF)

TRANSMITTER OUTPUT VOLTAGE (V)

VOUT+

VOUT-

VCC = +4.2V

-6

-2

-4

0 1000 1500500 2000 2500 3000

TRANSMITTER OUTPUT VOLTAGE

vs. LOAD CAPACITANCE

MAX3380E toc02

LOAD CAPACITANCE (pF)

TRANSMITTER OUTPUT VOLTAGE (V)

VOUT+

VOUT-

VCC = +2.5V

0 1000500 1500 2000 2500 3000

MAX3380E

SLEW RATE vs. LOAD CAPACITANCE

MAX3380E toc03

LOAD CAPACITANCE (pF)

SLEW RATE (V/μs)

VCC = +4.2V

VCC = +2.5V

Typical Operating Characteristics

(VCC = VL= +4.2V, C1 = 0.22µF, C2 = C3 = C4 = 1µF, C5 = 0.1µF parallel with 47µF, RL= 3kΩ, CL= 1000pF, data rate is 250kbps,

TA= +25°C, unless otherwise noted.)

MAX3380E/MAX3381E

+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers

with ±15kV ESD-Protected I/O and Logic Pins

4 _______________________________________________________________________________________

TIMING CHARACTERISTICS

(VCC = +2.35V to +5.5V, VL= +1.65V to +5.5V. When VCC < +4.5V, C1 = C2 = C3 = C4 = 0.1µF; when VCC ≥+4.5V, C1 = 0.047µF,

C2 = C3 = C4 = 0.33µF; TA= TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VL= +3.3V, TA= +25°C.)

PARAMETER

SYMBOL

CONDITIONS MIN

TYP MAX

UNITS

MAX3381E 250

Maximum Data Rate RL = 3kΩ, CL = 1000pF, one

transmitter switching MAX3380E 460

kbps

tPLH

0.15

Receiver Propagation Delay tPHL

Receiver input to receiver output, CL = 100pF 0.15

µs

Transmitter Skew

⏐tPHL- tPLH⏐

(Note 2)

200

Receiver Skew

⏐tPHL- tPLH⏐

50 ns

Transition Region Slew Rate

(MAX3380E)

VCC = +4.2V, -3.0V < T_OUT< +3.0V,

RL = 3kΩ, CL = 250pF to 1000pF, TA = +25°C

100

V/µs

Transition Region Slew Rate

(MAX3381E)

VCC = +4.2V, -3.0V < T_OUT< +3.0V,

RL = 3kΩ, CL = 150pF to 1000pF, TA = +25°C

630

V/µs

Transition Region Slew Rate

(MAX3380E)

VCC = +2.35V, -3.0V < T_OUT< +3.0V,

RL = 3kΩ, CL = 250pF to 1000pF, TA = +25°C

V/µs

Transition Region Slew Rate

(MAX3381E)

VCC = +2.35V, -3.0V < T_OUT< +3.0V,

RL = 3kΩ, CL = 250pF to 1000pF, TA = +25°C

V/µs

Note 2: Transmitter skew is measured at the transmitter zero crosspoint.

MAX3380E/MAX3381E

+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers

with ±15kV ESD-Protected I/O and Logic Pins

_______________________________________________________________________________________ 5

0 1000500 1500 2000 2500 3000

MAX3381E

SLEW RATE vs. LOAD CAPACITANCE

MAX3380E toc04

LOAD CAPACITANCE (pF)

SLEW RATE (V/μs)

VCC = +4.2V

VCC = +2.5V

0 1000500 1500 2000 2500 3000

SUPPLY CURRENT vs. LOAD CAPACITANCE

WHEN TRANSMITTING DATA

MAX3381E toc05

LOAD CAPACITANCE (pF)

SUPPLY CURRENT (mA)

460kbps

250kbps

20kbps

1 TRANSMITTER SWITCHING

-6

-2

-4

TRANSMITTER OUTPUT VOLTAGE

vs. SUPPLY VOLTAGE (VCC FALLING)

MAX3380E toc06

SUPPLY VOLTAGE (V)

TRANSMITTER OUTPUT VOLTAGE (V)

2.5 3.5 4.5 5.5

VOUT+

VOUT-

-6

-2

-4

TRANSMITTER OUTPUT VOLTAGE

vs. SUPPLY VOLTAGE (VCC RISING)

MAX3380E toc07

SUPPLY VOLTAGE (V)

TRANSMITTER OUTPUT VOLTAGE (V)

2.5 3.5 4.5 5.5

VOUT+

VOUT-

2.5 3.5 4.5 5.5

SUPPLY CURRENT

vs. SUPPLY VOLTAGE (VCC FALLING)

MAX3380E toc08

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (mA)

1 TRANSMITTER SWITCHING

1μs/div

T_IN

5V/div

T_OUT

5V/div

MAX3380E toc09

MAX3380E

DATASTREAM VCC = +4.2V

-5V

VCC = VL = +2.5V

1μs/div

T_IN

5V/div

T_OUT

5V/div

MAX3380E toc10

MAX3380E

DATASTREAM VCC = +2.5V

-5V

Typical Operating Characteristics (continued)

(VCC = VL= +4.2V, C1 = 0.22µF, C2 = C3 = C4 = 1µF, C5 = 0.1µF parallel with 47µF, RL= 3kΩ, CL= 1000pF, data rate is 250kbps,

TA= +25°C, unless otherwise noted.)

MAX3380E/MAX3381E

+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers

with ±15kV ESD-Protected I/O and Logic Pins

6 _______________________________________________________________________________________

Detailed Description

The MAX3380E/MAX3381E are RS-232 transceivers that

maximize battery life by reducing current consumption

at low battery levels. When the supply voltage is above

+3.7V, the RS-232 outputs are at ±5.5V, which is com-

pliant with the RS-232 standard. As the supply voltage

drops below the +3.1V set point, the RS-232 outputs

change to ±3.7V, which is compatible with the RS-232

standard. The outputs will remain at the compatible lev-

els until the supply voltage rises above +3.5V, where

they return to compliant levels. 400mV of hysteresis pro-

tects against power-supply bounce that may cause

numerous mode changes.

Most devices that use charge pumps to double and

invert voltages consume higher current when the supply

voltage is less than half of the required output voltage.

This is due to the fact that the charge pump is constant-

ly operating because the output voltage is below the

regulation voltage. This requires more supply current

because the output will never reach the regulation volt-

age and switch off. The MAX3380E/MAX3381E reduce

the output voltage requirement allowing the charge

pump to operate with supply voltages down to +2.35V.

Dual-Mode Regulated Charge-Pump

Voltage Converter

The MAX3380E/MAX3381Es’ internal power supply is a

dual-mode regulated charge pump. The output regula-

tion point depends on VCC and the direction in which

VCC moves through the switchover region of +2.95V <

VCC < +3.7V.

For supply voltages above +3.7V, the charge pump will

generate +5.5V at V+ and -5.5V at V-. The charge

pumps operate in a discontinuous mode. If the output

voltages are less than ±5.5V, the charge pumps are

enabled; if the output voltages exceed ±5.5V, the

charge pumps are disabled.

For supply voltages below +2.95V, the charge pump

will generate +4.0V at V+ and -4.0V at V-. The charge

pumps operate in a discontinuous mode.

Each charge pump requires a flying capacitor (C1, C2)

and a reservoir capacitor (C3, C4) to generate the V+

and V- supplies (see Typical Operating Circuit).

Pin Description

PIN NAME FUNCTION ESD

PROTECTED

1 C1+ Positive Terminal of Voltage-Doubler Charge-Pump Capacitor —

2 V+ +5.5V/+4.0V Generated by the Charge Pump —

3 C1- Negative Terminal of Voltage-Doubler Charge-Pump Capacitor —

4 C2+ Positive Terminal of Inverting Charge-Pump Capacitor —

5 C2- Negative Terminal of Inverting Charge-Pump Capacitor —

6 V- -5.5V/-4.0V Generated by the Charge Pump —

INVALID

INVALID is asserted if any inputs of the receivers are in an invalid state;

-0.3V < VR_IN < +0.3V —

8, 9 T_IN TTL/CMOS Transmitter Inputs Referenced to VL (T1IN, T2IN) ✔

10, 11

R_OUT

TTL/CMOS Receiver Outputs Referenced to VL (R2OUT, R1OUT) ✔

FORCEON

Force-On Input. Drive high to override automatic circuitry keeping transmitters on

(FORCEOFF must be high) (Table 1). ✔

13 VLLogic Level Supply. +1.65V to +5.5V, sets CMOS logic thresholds and CMOS

outputs. —

14, 15

R_IN RS-232 Receiver Inputs (R2IN, R1IN) ✔

16, 17

T_OUT RS-232 Transmitter Outputs (T2OUT, T1OUT) ✔

18 GND Ground —

FORCEOFF

Force-Off Input. Drive low to shut down transmitters and on-board power supply.

This overrides all automatic circuitry and FORCEON (Table 1). ✔

—

20 VCC +2.35V to +5.5V Supply Voltage

MAX3380E/MAX3381E

+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers

with ±15kV ESD-Protected I/O and Logic Pins

_______________________________________________________________________________________ 7

Voltage Generation in the

Switchover Region

The MAX3380E/MAX3381E include a switchover circuit

between RS-232-compliant and RS-232-compatible

modes that has approximately 400mV of hysteresis

around the switchover point. The hysteresis is shown in

Figure 1. This large hysteresis helps to avoid mode

change under battery or power-supply bounce.

Under a decaying VCC, the charge pump will generate

an output voltage of ±5.5V with a VCC input range

between +3.1V and +5.5V. When VCC drops below the

switchover point of +3.1V, the charge pump switches

into RS-232-compatible mode generating ±4V.

When VCC is rising, the charge pump will generate an

output voltage of ±4.0V, while VCC is between +2.5V

and +3.5V. When VCC rises above the switchover volt-

age of +3.5V, the charge pump switches to RS-232-

compliant mode to generate an output voltage of ±5.5V.

RS-232 Transmitters

The transmitters are inverting level translators that con-

vert CMOS-logic levels to RS-232-compatible levels.

The MAX3380E/MAX3381E will automatically reduce

the RS-232-compliant levels from ±5.5V to ±3.7V when

VCC falls below approximately +3.1V. The reduced lev-

els are RS-232-compatible and reduce supply current

requirements that help preserve the battery. Built-in

hysteresis of approximately 400mV for VCC ensures

that the RS-232 output levels do not change if VCC is

noisy or has a sudden current draw causing the supply

voltage to drop slightly. The outputs will return to RS-

232-compliant levels (±5.5V) when VCC rises above

approximately +3.5V.

The MAX3380E/MAX3381E transmitters guarantee a data

rate of 460kbps/250kbps, respectively, with worst-case

loads of 3kΩin parallel with 1000pF. Transmitters can be

paralleled to drive multiple receivers.

When FORCEOFF is driven to ground, the transmitters

are disabled and the outputs go into high impedance;

receivers remain active. When the AutoShutdown Plus

circuitry senses that all receiver and transmitter inputs

are inactive for more than 30s, the transmitters are dis-

abled and the outputs go into a high-impedance state,

and the receivers remain active. When the power is off,

the MAX3380E/MAX3381E permit the outputs to be dri-

ven up to ±12V.

The transmitter inputs have a 400kΩactive positive

feedback resistor. They will retain a valid logic level if

the driving signal is removed or goes high impedance.

Connect unused transmitter inputs to VCC or ground.

RS-232 Receivers

The receivers convert RS-232 signals to logic levels

referred to VL. Both receivers are active in shutdown

(Table 1).

AutoShutdown Plus Mode

The MAX3380E/MAX3381E achieve a 1µA supply current

with Maxim’s AutoShutdown Plus feature, which operates

when FORCEOFF is high and FORCEON is low. When

these devices do not sense a valid signal transition on

any receiver and transmitter input for 30s, the on-board

charge pumps are shut down, reducing supply current

to 1µA. This occurs if the RS-232 cable is disconnected

or if the connected peripheral transmitters are turned off,

and if the UART driving the transmitter inputs is inactive.

The system turns on again when a valid transition is

applied to any RS-232 receiver or transmitter input. As a

result, the system saves power without changes to the

existing BIOS or operating system.

Figures 2a and 2b show valid and invalid RS-232

receiver voltage levels. INVALID indicates the receiver

input’s condition, and is independent of the FORCEON

and FORCEOFF states. Figure 2 and Table 1 summa-

rize the MAX3380E/MAX3381E’s operating modes.

FORCEON and FORCEOFF override AutoShutdown

Plus circuitry. When neither control is asserted, the IC

selects between these states automatically based on

the last receiver or transmitter input edge received.

By connecting FORCEON to INVALID, the MAX3380E/

MAX3381E is shut down when no valid receiver level and

no receiver or transmitter edge is detected for 30s, and

wakes up when a receiver or transmitter edge is detect-

ed (Figure 2c).

20ms/div

VCC

2V/div

V+

2V/div

+4.5V

+2.5V

+5.8V

+4.4V

Figure 1. V+ Switchover for Changing Vcc

MAX3380E/MAX3381E

+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers

with ±15kV ESD-Protected I/O and Logic Pins

8 _______________________________________________________________________________________

+0.3V

-0.3V

INVALID

R_IN

INVALID ASSERTED IF ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR

AT LEAST 30μs.

30µs

TIMER

+2.7V

-2.7V

INVALID

R_IN

INVALID DEASSERTED IF ANY RECEIVER INPUT HAS BEEN BETWEEN +2.7V AND -2.7V

FOR LESS THAN 30μs.

0.3μs

TIMER

Figure 2a. I

NVALID

Functional Diagram, I

NVALID

Low Figure 2b. I

NVALID

Functional Diagram, I

NVALID

High

Table 1. AutoShutdown Plus Truth Table

OPERATION

STATUS

FORCEON

FORCEOFF

VALID

RECEIVER

LEVEL

RECEIVER OR

TRANSMITTER EDGE

WITHIN 30s

T_OUT R_OUT

Shutdown

(Forced Off) X 0 X X High-Z Active

Normal Operation

(Forced On) 1 1 X X Active Active

Normal Operation

(AutoShutdown

Plus)

0 1 X Yes Active Active

Shutdown

(AutoShutdown

Plus)

0 1 X No High-Z Active

Normal Operation

INVALID 1 Yes X Active Active

Normal Operation

INVALID 1 X Yes Active Active

Shutdown INVALID 1 No No High-Z Active

Normal Operation

(AutoShutdown) INVALID INVALID Yes X Active Active

Shutdown

(AutoShutdown) INVALID INVALID No X High-Z Active

X = Don’t care

MAX3380E/MAX3381E

+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers

with ±15kV ESD-Protected I/O and Logic Pins

_______________________________________________________________________________________ 9

By connecting FORCEON and FORCEOFF to INVALID,

the MAX3380E/MAX3381E are shut down when no valid

receiver level is detected.

VLLogic Supply Input

Unlike other RS-232 interface devices where the receiv-

er outputs swing between 0 and VCC, the MAX3380E/

MAX3381E feature a separate logic supply input (VL)

that sets VOH for the receiver and INVALID outputs. VL

also sets the threshold for the transmitter inputs,

FORCEON and FORCEOFF. This feature allows a great

deal of flexibility in interfacing to many different types of

systems with different logic levels. Connect this input to

+2.7V

+0.3V

-0.3V

-2.7V

TRANSMITTERS ENABLED, INVALID HIGH

INDETERMINATE

AutoShutdown, TRANSMITTERS DISABLED,

1μA SUPPLY CURRENT INVALID LOW

INDETERMINATE

TRANSMITTERS ENABLED, INVALID HIGH

POWERDOWN*

AUTOSHDN

FORCEOFF

FORCEON

* POWERDOWN IS ONLY AN INTERNAL SIGNAL.

IT CONTROLS THE OPERATIONAL STATUS OF

THE TRANSMITTERS AND THE POWER SUPPLIES.

Figure 2d. Power-Down Logic

AUTOSHDN

R_IN

T_IN

30s

TIMER

EDGE

DETECT

EDGE

DETECT

FORCEOFF

FORCEON

Figure 2c. AutoShutdown Plus Logic

V+

V-

VCC

INVALID

OUTPUT

TRANSMITTER

INPUTS

RECEIVER

INPUTS }INVALID

REGION

TRANSMITTER

OUTPUTS

tAUTOSHDN tWU tWU

tINVL tINVH tAUTOSHDN

Figure 4. AutoShutdown Plus/

INVALID

Timing Diagram

Figure 3. AutoShutdown Trip Levels

MAX3380E/MAX3381E

the host logic supply (+1.65V to +5.5V). The VLinput

will draw a maximum current of 20µA with receiver out-

puts unloaded.

±15kV ESD Protection

Maxim has developed state-of-the-art structures to pro-

tect these pins against an ESD of ±15kV without dam-

age. The ESD structures withstand high ESD in all states:

normal operation, shutdown, and power-down. After an

ESD event, Maxim’s “E” version devices keep working

without latch-up, whereas competing RS-232 products

can latch and must be powered down to remove latch-

up. ESD protection can be tested in various ways. The

transmitter and receiver outputs and receiver and logic

inputs of this product family are characterized for protec-

tion to the following limits:

• ±15kV using the Human Body Model

• ±8kV using the Contact Discharge method speci-

fied in IEC 1000-4-2

• ±15kV using IEC 1000-4-2’s Air-Gap Discharge

method

ESD Test Conditions

ESD performance depends on a variety of conditions.

Contact Maxim for a reliability report that documents

test setup, methodology, and results.

Human Body Model

Figure 5a shows the Human Body Model, and Figure

5b shows the current waveform it generates when dis-

charged into a low impedance. This model consists of

a 100pF capacitor charged to the ESD voltage of inter-

est, which is then discharged into the test device

through a 1.5kΩresistor.

IEC 1000-4-2

The IEC 1000-4-2 standard covers ESD testing and

performance of finished equipment; it does not specifi-

cally refer to ICs. The MAX3380E/MAX3381E help you

design equipment that meets Level 4, the highest level

of IEC 1000-4-2 without the need for additional ESD-

protection components. The major difference between

tests done using the Human Body Model and IEC

1000-4-2 is higher peak current in IEC 1000-4-2,

because series resistance is lower in the IEC 1000-4-2

model. Hence, the ESD withstand voltages measured

+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers

with ±15kV ESD-Protected I/O and Logic Pins

10 ______________________________________________________________________________________

CHARGE-CURRENT

LIMIT RESISTOR

DISCHARGE

RESISTANCE

STORAGE

CAPACITOR

100pF

1MΩ

1500Ω

HIGH-

VOLTAGE

SOURCE

DEVICE

UNDER

TEST

Figure 5a. Human Body ESD Test Model

CHARGE-CURRENT

LIMIT RESISTOR

DISCHARGE

RESISTANCE

STORAGE

CAPACITOR

150pF

50MΩ to 100MΩ

330Ω

HIGH-

VOLTAGE

SOURCE

DEVICE

UNDER

TEST

Figure 6a. IEC 1000-4-2 ESD Test Model

IP 100%

90%

36.8%

tRL TIME

tDL

CURRENT WAVEFORM

PEAK-TO-PEAK RINGING

(NOT DRAWN TO SCALE)

10%

AMPERES

Figure 5b. Human Body Current Waveform

100%

90%

60ns

10%

tr = 0.7ns to 1ns

IPEAK

30ns t

Figure 6b. IEC 1000-4-2 ESD Generator Current Waveform

MAX3380E/MAX3381E

+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers

with ±15kV ESD-Protected I/O and Logic Pins

______________________________________________________________________________________ 11

to IEC 1000-4-2 are generally lower than that measured

using the Human Body Model. Figure 6a shows the IEC

1000-4-2 model, and Figure 6b shows the current

waveform for the ±8kV IEC 1000-4-2 Level 4 ESD

Contact Discharge test.

The Air-Gap test involves approaching the device with

a charged probe. The Contact Discharge method con-

nects the probe to the device before the probe is ener-

gized.

Machine Model

The Machine Model for ESD tests all pins using a

200pF storage capacitor and zero discharge resis-

tance. Its objective is to emulate the stress caused by

contact that occurs with handling and assembly during

manufacturing. All pins require this protection during

manufacturing, not just RS-232 inputs and outputs.

Therefore, after PC board assembly, the Machine

Model is less relevant to I/O ports.

Applications Information

Capacitor Selection

The capacitor type used for C1–C4 is not critical for

proper operation. Polarized or nonpolarized capacitors

can be used. The charge pump requires 0.1µF capaci-

tors for +3.3V operation. For other supply voltages, see

Table 2 for required capacitor values. Do not use val-

ues smaller than those listed in Table 2. Increasing the

capacitor values (e.g., by a factor of 2) reduces ripple

on the transmitter outputs and slightly reduces power

consumption. C2, C3, and C4 can be increased without

changing C1’s value. However, do not increase C1

without also increasing the values of C2, C3, C4, and

C5 to maintain the proper ratios (C1 to the other capac-

itors).

When using the minimum required capacitor values,

make sure the capacitor value does not degrade

excessively with temperature. If in doubt, use capaci-

tors with a large nominal value. The capacitor’s equiva-

lent series resistance (ESR) usually rises at low

temperatures and influences the amount of ripple on

V+ and V-.

Power-Supply Decoupling

In most circumstances, connect a 0.1µF capacitor from

VCC to GND. This capacitor is for noise reduction. If the

MAX3380E/MAX3381E are used in a data cable appli-

cation, add a 47µF capacitor from VCC to ground. The

47µF capacitor is used to ensure that the current need-

ed during power-up is supplied to the device. In appli-

cations that are sensitive to power-supply noise,

decouple VCC to ground with a capacitor of the same

value as charge-pump capacitor C1. Connect bypass

capacitors as close to the IC as possible.

Transmitter Outputs when Recovering

from Shutdown

Figure 7 shows two transmitter outputs when exiting

shutdown mode. As they become active, the two trans-

mitter outputs are shown going to opposite RS-232 lev-

els (one transmitter input is high, the other is low). Each

transmitter is loaded with 3kΩin parallel with 1000pF.

The transmitter outputs display no ringing or undesir-

able transients as they come out of shutdown. Note that

the transmitters are enabled only when the magnitude

of V- exceeds approximately 3V.

High Data Rates

The MAX3380E/MAX3381E maintain the RS-232 ±5.0V

minimum transmitter output voltage even at high data

rates. Figure 8 shows a transmitter loopback test cir-

cuit. Figure 9 shows a loopback test result for the

MAX3380E at 460kbps with true RS-232 output voltage

levels (VCC = +4.2V). Figure 10 shows the same test

with RS-232-compatible levels (VCC = +2.5V). With

data rates as high as 460kbps, the MAX3380E is com-

patible with 2.5-Generation GSM standards.

VCC (V) C1, C5 (µF)

C2, C3, C4 (µF)

+2.35 to +3.6 0.1 0.1

+4.5 to +5.5 0.047 0.33

+2.35 to +5.5 0.22 1

Table 2. Minimum Required Capacitor

Values

VCC = 3.3V, C1–C4 = 0.1μF, CLOAD = 1000pF

4μs/div

5V/div

2V/div

T2OUT

T1OUT

FORCEON =

FORCEOFF

Figure 7. Transmitter Outputs when Recovering from Shutdown

or Powering Up

MAX3380E/MAX3381E

+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers

with ±15kV ESD-Protected I/O and Logic Pins

12 ______________________________________________________________________________________

For Figure 9 and Figure 10, a single transmitter was dri-

ven at 460kbps, and all transmitters were loaded with

an RS-232 receiver in parallel with 1000pF.

Data Cable Applications

The MAX3380E/MAX3381Es’ ±15kV ESD protection on

both the RS-232 I/Os as well as the logic I/Os makes

them ideal candidates for data cable applications. A

data cable is both an electrical connection and a level

translator, allowing ultra-miniaturization of cell phones

and other small portable devices.

Previous data cable approaches suffered from com-

plexity due to the required protection circuits on both

the logic side of the cable, as well as on the RS-232

connections. The example shown in Figure 11 shows

the ease of using the MAX3380E/MAX3381E in data

cable applications. For best performance, keep the

logic level lines short and use the RS-232 level lines to

span any distance.

VCC = VL = +2.5V, C1 = 0.1μF, C2 = C3 = C4 = 1μF,

CLOAD = 1000pF

TIME (1μs/div)

T1IN

2V/div

T1OUT

5V/div

R1OUT

2V/div

-5V

Figure 10. Loopback Test Results at 460kbps (VCC = +2.5V)

VCC = VL = +4.2V, C1 = 0.1μF, C2 = C3 = C4 = 1μF,

CLOAD = 1000pF

1μs/div

T1IN

5V/div

T1OUT

5V/div

R1OUT

5V/div

-5V

Figure 9. Loopback Test Results at 460kbps (VCC = +4.2V)

MAX3380E

MAX3381E

5kΩ

R_ IN

R_ OUT

C2-

C2+

C1-

C1+

V-

V+

VCC

FORCEOFF

T_ OUT

T_ IN

GND

VCC

FORCEON 1000pF

Figure 8. Loopback Test Circuit

MAX3380E/MAX3381E

+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers

with ±15kV ESD-Protected I/O and Logic Pins

______________________________________________________________________________________ 13

MAX3380E/

MAX3381E

CELL PHONE

LOGIC LEVELS

R2OUT

R1OUT

T2IN

T1IN

C1+

C1-

R2IN

R1IN

T2OUT

T1OUT

V+

VCC

V-

CTS

RTS

VBATT

0.1μF

PERIPHERALS

RS-232 LEVELS

RTS I/O

CTS

INVALID

FORCEON

FORCEOFF

C2+

C2-

0.1μF

0.1μF47μF

Figure 11. Typical Application Circuit

Chip Information

TRANSISTOR COUNT: 1467

PROCESS: BiCMOS

VCC

FORCEOFF

GND

T1OUTC2+

C1-

V+

C1+

TOP VIEW

T2OUT

R1IN

R2IN

T1IN

INVALID

V-

C2-

FORCEON

R1OUTR2OUT

T2IN

MAX3380E/

MAX3381E

TSSOP

Pin Configuration

MAX3380E/MAX3381E

+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers

with ±15kV ESD-Protected I/O and Logic Pins

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.

14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

TSSOP4.40mm.EPS

PACKAGE OUTLINE, TSSOP 4.40mm BODY

21-0066

Package Information (continued)

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,

go to www.maxim-ic.com/packages.)