Datasheet MAX3380E, MAX3381E Datasheet (MAXIM)

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General Description

The MAX3380E/MAX3381E are +2.35V to +5.5V-pow­ered EIA/TIA-232 and V.28/V.24 communication inter­faces 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 Air­Gap 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-compati­ble levels with no increase in supply current for sup­plies 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 auto­matically enter a 1µA shutdown mode. These
devices shut down the on-board power supply and
drivers when they do not sense a valid signal transi­tion for 30 seconds on either the receiver or trans­mitter 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 V

L

pin that
allows interoperation in mixed-logic voltage systems
down to +1.65V. Both input and output logic levels
are referenced to the V

L

pin. 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

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+

V

CCVL

C1

0.1µF

C2

0.1µF

C5

0.1µF

+3.3V

RS-232
INPUTS

TTL/CMOS

OUTPUTS

5kΩ

5kΩ

C3

0.1µF

C4

0.1µF

V

L

V

L

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

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

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; T

A

= T

MIN

to T

MAX

, 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.

V

CC

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

V

L

to 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 (V

L

+ 0.3V)

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

Continuous Power Dissipation (T

A

= +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

Supply Current, AutoShutdown
Plus

Receivers idle, VT_IN = VCC or GND,

I

CC

FORCEON = GND, FORCEOFF = V
FORCEOFF = GND 1 10

CC

10

µA

Supply Current, Normal Operation I

LOGIC INPUTS (T_IN, FORCEON, FORCEOFF)

Input Logic Threshold Low V

Input Logic Threshold High V

Transmitter Input Hysteresis 0.5 V

Input Leakage Current ±0.01 ±1µA

RECEIVER OUTPUTS (R_OUT) AND INVALID

Output Voltage Low I

Output Voltage High I

RECEIVER INPUTS (R_IN)

Input Voltage Range -25 +25 V

Input Threshold Low TA = +25°C

Input Threshold High TA = +25°C

Input Hysteresis 0.3 V

Input Resistance TA = +25°C 357kΩ

CC

FORCEON = FORCEOFF = VL, no load 0.3 1 mA

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

IL

VCC = +2.5V, VL = +1.65V 0.4

VCC = +5.5V, VL = +5.5V VL ✕ 0.66

IH

VCC = +2.5V, VL = +1.65V VL ✕ 0.66

= 500µA 0.5 V

OUT

= -500µA VL - 0.4 VL - 0.2 V

OUT

VL = +3.3V 0.6 1.2

V

= +5.0V 0.8 1.5

L

VL = +3.3V 1.5 2.4

V

= +5.0V 1.8 2.4

L

V

V

V

V

MAX3380E/MAX3381E

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

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

_______________________________________________________________________________________ 3

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; T

A

= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at VCC= VL= +3.3V, TA= +25°C.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

AutoShutdown Plus (FORCEON = GND, FORCEOFF = VL)

Receiver Input Threshold to
INVALID Output High

Receiver Input Threshold to
INVALID Output Low

Receiver Positive or Negative
Threshold to INVALID High

Receiver Positive or Negative
Threshold to INVALID Low

Receiver or Transmitter Edge to
Transmitters Enabled

Receiver or Transmitter Edge to
Transmitters Shutdown

TRANSMITTER OUTPUTS

VCC Mode Switch Point
(V

Falling)

CC

VCC Mode Switch Point

Rising)

(V

CC

VCC Mode Switch Point
Hysteresis

Output Voltage Swing

Output Resistance VCC = 0, transmitter output = ±2.0V 300 10M Ω

Output Short-Circuit Current ±60 mA

Output Leakage Current V

ESD PROTECTION

R_IN, T_OUT, R_OUT, T_IN,
FORCEON, FORCEOFF

Figure 3

Figure 3 -0.3 0.3 V

t

INVL

t

INVH

t

WU

t

AU T OS H D N VCC

VCC = +5.0V, Figure 4 0.3 µs

VCC = +5.0V, Figure 4 30 µs

VCC = +5.0V, Figure 4 15 µs

T_OUT = ±5.0V to ±3.7V 2.95 3.1 3.25 V

T_OUT = ±3.7V to ±5.5V 3.3 3.5 3.7 V

All transmitter
outputs loaded
with 3kΩ to ground

Human Body Model ±15

IEC 1000-4-2 Air-Gap Discharge Method ±15

IEC 1000-4-2 Contact Discharge Method ±8

= +5.0V, Figure 4 30 s

= ±12V, transmitters disabled ±25 µA

OUT

Positive threshold 2.7

Negative threshold -2.7

V

= + 3.25V to + 5.5V ,

C C

fal l i ng

V

C C

= + 2.5V to + 2.95V ,

V

C C

fal l i ng

V

C C

±5 ±5.4

±3.7

V

400 mV

V

kV

-6

-2

-4

2

0

6

4

8

0 1000 1500500 2000 2500 3000

TRANSMITTER OUTPUT VOLTAGE

vs. LOAD CAPACITANCE

MAX3380E toc01

LOAD CAPACITANCE (pF)

TRANSMITTER OUTPUT VOLTAGE (V)

V

OUT+

V

OUT-

VCC = +4.2V

-6

-2

-4

2

0

6

4

8

0 1000 1500500 2000 2500 3000

TRANSMITTER OUTPUT VOLTAGE

vs. LOAD CAPACITANCE

MAX3380E toc02

LOAD CAPACITANCE (pF)

TRANSMITTER OUTPUT VOLTAGE (V)

V

OUT+

V

OUT-

VCC = +2.5V

0

5

10

15

20

25

30

35

40

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; T

A

= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at VCC= VL= +3.3V, TA= +25°C.)

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

PARAMETER SYMBOL CONDITIONS MIN TYP MAX

Maximum Data Rate

Receiver Propagation Delay

Transmitter Skew t
Receiver Skew t

Transition Region Slew Rate
(MAX3380E)

Transition Region Slew Rate
(MAX3381E)

Transition Region Slew Rate
(MAX3380E)

Transition Region Slew Rate
(MAX3381E)

UNITS

MAX3381E 250

MAX3380E 460

20 100 V/µs

6 30 V/µs

kbps

0.15

0.15

30 V/µs

10 V/µs

PHL

PHL

R

= 3kΩ, CL = 1000pF, one

L

transmitter switching

t

PLH

t

PHL

- t

- t

Receiver input to receiver output, CL = 100pF

 (Note 2) 200 ns

PLH

 50 ns

PLH

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

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

R

L

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

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

R

L

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

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

R

L

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

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

L

µs

MAX3380E/MAX3381E

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

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

_______________________________________________________________________________________ 5

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,
T

A

= +25°C, unless otherwise noted.)

SLEW RATE vs. LOAD CAPACITANCE

MAX3381E

14

13

12

11

10

9

SLEW RATE (V/µs)

8

7

6

0 1000500 1500 2000 2500 3000

VCC = +4.2V

VCC = +2.5V

LOAD CAPACITANCE (pF)

TRANSMITTER OUTPUT VOLTAGE

vs. SUPPLY VOLTAGE (V

8

6

V

OUT+

4

2

MAX3380E toc04

SUPPLY CURRENT vs. LOAD CAPACITANCE

WHEN TRANSMITTING DATA

80

1 TRANSMITTER SWITCHING

70

60

50

40

30

SUPPLY CURRENT (mA)

20

10

0

01000500 1500 2000 2500 3000

LOAD CAPACITANCE (pF)

RISING)

CC

MAX3380E toc07

460kbps

MAX3381E toc05

250kbps

20kbps

SUPPLY CURRENT

vs. SUPPLY VOLTAGE (V

25

1 TRANSMITTER SWITCHING

20

15

TRANSMITTER OUTPUT VOLTAGE

vs. SUPPLY VOLTAGE (V

8

6

V

OUT+

4

2

0

-2

V

OUT-

TRANSMITTER OUTPUT VOLTAGE (V)

-4

-6

2.5 3.5 4.5 5.5

FALLING)

CC

SUPPLY VOLTAGE (V)

CC

MAX3380E toc08

FALLING)

MAX3380E toc06

0

-2

V

TRANSMITTER OUTPUT VOLTAGE (V)

OUT-

-4

-6

2.5 3.5 4.5 5.5
SUPPLY VOLTAGE (V)

MAX3380E

1µs/div

= +4.2V

CC

DATASTREAM V

T_IN

5V/div

T_OUT

5V/div

MAX3380E toc09

5V

0

5V

0

-5V

10

SUPPLY CURRENT (mA)

5

0

2.5 3.5 4.5 5.5
SUPPLY VOLTAGE (V)

MAX3380E

1µs/div

= +2.5V

CC

T_IN

5V/div

T_OUT

5V/div

DATASTREAM V

VCC = V

+2.5V

L =

MAX3380E toc10

5V

0

5V

0

-5V

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 com­pliant 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 lev­els until the supply voltage rises above +3.5V, where
they return to compliant levels. 400mV of hysteresis pro­tects 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 constant­ly operating because the output voltage is below the
regulation voltage. This requires more supply current
because the output will never reach the regulation volt­age 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 regula­tion point depends on VCCand the direction in which
VCCmoves 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

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 —

7 INVALID

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) ✔

12 FORCEON

13 V

14, 15 R_IN RS-232 Receiver Inputs (R2IN, R1IN) ✔

16, 17 T_OUT RS-232 Transmitter Outputs (T2OUT, T1OUT) ✔

18 GND Ground —

19 FORCEOFF

20 V

CC

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

-0.3V < V

Force-On Input. Drive high to override automatic circuitry keeping transmitters on
(FORCEOFF must be high) (Table 1).

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

L

outputs.

Force-Off Input. Drive low to shut down transmitters and on-board power supply.
This overrides all automatic circuitry and FORCEON (Table 1).

+2.35V to +5.5V Supply Voltage

R_IN

< +0.3V

ESD

PROTECTED

—

✔

—

✔

—

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 VCCinput range
between +3.1V and +5.5V. When VCCdrops below the
switchover point of +3.1V, the charge pump switches
into RS-232-compatible mode generating ±4V.

When VCCis rising, the charge pump will generate an
output voltage of ±4.0V, while VCCis between +2.5V
and +3.5V. When VCCrises above the switchover volt­age of +3.5V, the charge pump switches to RS-232­compliant mode to generate an output voltage of ±5.5V.

RS-232 Transmitters

The transmitters are inverting level translators that con­vert 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
VCCfalls below approximately +3.1V. The reduced lev­els are RS-232-compatible and reduce supply current
requirements that help preserve the battery. Built-in
hysteresis of approximately 400mV for VCCensures
that the RS-232 output levels do not change if VCCis
noisy or has a sudden current draw causing the supply
voltage to drop slightly. The outputs will return to RS­232-compliant levels (±5.5V) when VCCrises above
approximately +3.5V.

The MAX3380E/MAX3381E transmitters guarantee a data
rate of 460kbps/250kbps, respectively, with worst-case
loads of 3kΩ in 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 dis­abled 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 dri­ven up to ±12V.

The transmitter inputs have a 400kΩ active 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 VCCor 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 detect­ed (Figure 2c).

Figure 1. V+ Switchover for Changing Vcc

V

CC

2V/div

V+

2V/div

20ms/div

+4.5V

+2.5V

+5.8V

+4.4V

MAX3380E/MAX3381E

+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins

8 _______________________________________________________________________________________

Figure 2a. I

NVALID

Functional Diagram, I

NVALID

Low

Figure 2b. I

NVALID

Functional Diagram, I

NVALID

High

Table 1. AutoShutdown Plus Truth Table

X = Don’t care

OPERATION

STATUS

Shutdown
(Forced Off)

VALID

FORCEON FORCEOFF

X 0 X X High-Z Active

RECEIVER

LEVEL

RECEIVER OR

TRANSMITTER EDGE

WITHIN 30s

T_OUT R_OUT

Normal Operation
(Forced On)

Normal Operation
(AutoShutdown
Plus)

Shutdown
(AutoShutdown
Plus)

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)

Shutdown
(AutoShutdown)

+0.3V

1 1 X X Active Active

0 1 X Yes Active Active

0 1 X No High-Z Active

INVALID INVALID Yes X Active Active

INVALID INVALID No X High-Z Active

+2.7V

R_IN

-0.3V

INVALID ASSERTED IF ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR
AT LEAST 30µs.

30µs

TIMER

R

INVALID

R_IN

-2.7V

INVALID DEASSERTED IF ANY RECEIVER INPUT HAS BEEN BETWEEN +2.7V AND -2.7V
FOR LESS THAN 30µs.

0.3µs

TIMER

R

INVALID

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 receiv­er outputs swing between 0 and VCC, the MAX3380E/
MAX3381E feature a separate logic supply input (VL)
that sets VOHfor the receiver and INVALID outputs. V

L

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

Figure 2d. Power-Down Logic

Figure 2c. AutoShutdown Plus Logic

Figure 4. AutoShutdown Plus/

INVALID

Timing Diagram

Figure 3. AutoShutdown Trip Levels

EDGE

T_IN

DETECT

EDGE

R_IN

DETECT

FORCEON

TRANSMITTERS ENABLED, INVALID HIGH

+2.7V

+0.3V

-0.3V

-2.7V

AutoShutdown, TRANSMITTERS DISABLED,

0

TRANSMITTERS ENABLED, INVALID HIGH

INDETERMINATE

1µA SUPPLY CURRENT INVALID LOW

INDETERMINATE

FORCEOFF

S

30s

TIMER

R

AUTOSHDN

FORCEOFF

FORCEON

AUTOSHDN

* POWERDOWN IS ONLY AN INTERNAL SIGNAL.
IT CONTROLS THE OPERATIONAL STATUS OF
THE TRANSMITTERS AND THE POWER SUPPLIES.

POWERDOWN*

RECEIVER

INPUTS

TRANSMITTER

INPUTS

TRANSMITTER

OUTPUTS

INVALID
OUTPUT

V

L

t

INVL

0

V+

V

CC

0

V-

t

INVH

t

AUTOSHDN

INVALID

}

REGION

t

t

WU

AUTOSHDN

t

WU

MAX3380E/MAX3381E

the host logic supply (+1.65V to +5.5V). The VLinput
will draw a maximum current of 20µA with receiver out­puts unloaded.

±15kV ESD Protection

Maxim has developed state-of-the-art structures to pro­tect these pins against an ESD of ±15kV without dam­age. 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 latch­up. 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 protec­tion 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 dis­charged into a low impedance. This model consists of
a 100pF capacitor charged to the ESD voltage of inter­est, which is then discharged into the test device
through a 1.5kΩ resistor.

IEC 1000-4-2

The IEC 1000-4-2 standard covers ESD testing and
performance of finished equipment; it does not specifi­cally 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 ESD­protection 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 ______________________________________________________________________________________

Figure 5a. Human Body ESD Test Model

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

Figure 5b. Human Body Current Waveform

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

R

D

1500Ω

DISCHARGE
RESISTANCE

STORAGE
CAPACITOR

DEVICE
UNDER

TEST

HIGH-

VOLTAGE

DC

SOURCE

R

C

1MΩ

CHARGE-CURRENT

LIMIT RESISTOR

C

s

100pF

IP 100%

90%

AMPERES

36.8%

10%

0

0

t

RL

TIME

t

DL

CURRENT WAVEFORM

PEAK-TO-PEAK RINGING

I

r

(NOT DRAWN TO SCALE)

R

D

330Ω

DISCHARGE

RESISTANCE

STORAGE
CAPACITOR

HIGH-

VOLTAGE

DC

SOURCE

R

C

50MΩ to 100MΩ

CHARGE-CURRENT

LIMIT RESISTOR

C

s

150pF

I

100%

90%

PEAK

I

10%

tr = 0.7ns to 1ns

30ns

60ns

DEVICE
UNDER

TEST

t

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 con­nects the probe to the device before the probe is ener­gized.

Machine Model

The Machine Model for ESD tests all pins using a
200pF storage capacitor and zero discharge resis­tance. 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 capaci­tors for +3.3V operation. For other supply voltages, see
Table 2 for required capacitor values. Do not use val­ues 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 capac­itors).

When using the minimum required capacitor values,
make sure the capacitor value does not degrade
excessively with temperature. If in doubt, use capaci­tors with a large nominal value. The capacitor’s equiva­lent 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
VCCto GND. This capacitor is for noise reduction. If the
MAX3380E/MAX3381E are used in a data cable appli­cation, add a 47µF capacitor from VCCto ground. The
47µF capacitor is used to ensure that the current need­ed during power-up is supplied to the device. In appli­cations that are sensitive to power-supply noise,
decouple VCCto 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 trans­mitter outputs are shown going to opposite RS-232 lev­els (one transmitter input is high, the other is low). Each
transmitter is loaded with 3kΩ in parallel with 1000pF.
The transmitter outputs display no ringing or undesir­able 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 cir­cuit. 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 com­patible with 2.5-Generation GSM standards.

Table 2. Minimum Required Capacitor
Values

Figure 7. Transmitter Outputs when Recovering from Shutdown
or Powering Up

FORCEON =

5V
0

5V/div

2V/div

6V

0

FORCEOFF
T2OUT

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

T1OUT
6V

4µs/div

VCC = 3.3V, C1–C4 = 0.1µF, C

LOAD

= 1000pF

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 dri­ven 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 com­plexity 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.

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

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

Figure 8. Loopback Test Circuit

V

C1

C2

CC

C5

V

V

CC

C1+

C1-

C2+

C2-

MAX3380E
MAX3381E

L

V+

C3

V-

C4

T1IN

5V/div

T1OUT

5V/div

R1OUT

5V/div

1µs/div

VCC = V

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

L =

= 1000pF

C

LOAD

T1IN

2V/div

T1OUT

5V/div

R1OUT

2V/div

5V

0

5V

0

-5V

5V

0

2V

0

5V

0

-5V

2V

0

T_ IN

R_ OUT

FORCEON

V

CC

FORCEOFF

GND

T_ OUT

R_ IN

5kΩ

1000pF

VCC = V
C

LOAD

TIME (1µs/div)

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

L =

= 1000pF

MAX3380E/MAX3381E

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

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

______________________________________________________________________________________ 13

Figure 11. Typical Application Circuit

Chip Information

TRANSISTOR COUNT: 1467

PROCESS: BiCMOS

20

19

18

17

16

15

14

13

1

2

3

4

5

6

7

8

V

CC

FORCEOFF

GND

T1OUTC2+

C1-

V+

C1+

TOP VIEW

T2OUT

R1IN

R2IN

V

L

T1IN

INVALID

V-

C2-

12

11

9

10

FORCEON

R1OUTR2OUT

T2IN

MAX3380E/

MAX3381E

TSSOP

Pin Configuration

0.1µF47µF

V

BATT

CELL PHONE

LOGIC LEVELS

Tx

RTS

Rx

CTS

0.1µF

0.1µF

V

C1+

C1-

C2+

C2-

T1IN

T2IN

R1OUT

R2OUT

CC

MAX3380E/

MAX3381E

V

L

FORCEOFF

FORCEON

T1OUT

T2OUT

R1IN

R2IN

INVALID

V+

V-

0.1µF

0.1µF

PERIPHERALS

RS-232 LEVELS

Tx

CTS

Rx

RTS

I/O

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

© 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

Package Information

TSSOP.EPS