MAXIM MAX3238 Technical data

_______________General Description

The MAX3238 true RS-232 transceiver achieves a
1µA supply current with Maxim’s revolutionary
AutoShutdown Plus™ feature. When the device does
not sense a valid signal transition on either the receiver
or transmitter inputs within 30sec, the on-board power
supply and drivers shut down. This occurs if the RS-232
cable is disconnected or if the transmitters of the con­nected peripheral are inactive. The system turns on
again when a valid transition is applied to any RS-232
receiver or transmitter input, saving power without
changes to the existing BIOS or operating system.

The MAX3238 5-driver/3-receiver complete serial port is
a 3V-powered EIA/TIA-232 and V.28/V.24 communica­tions interface intended for notebook or subnotebook
computer applications. A proprietary, high-efficiency,
dual charge-pump power supply and a low-dropout
transmitter combine to deliver true RS-232 performance
from a single +3.0V to +5.5V supply. A guaranteed
data rate of 250kbps provides compatibility with popu­lar software for communicating with personal comput­ers. The MAX3238 requires only 0.1µF capacitors in

3.3V operation. It is ideal for 3.3V-only systems, mixed

3.3V and 5.0V systems, or 5V-only systems that require
true RS-232 performance.

Receiver R1 has an extra, always-active output (in addi­tion to its standard output), which allows external
devices, such as a modem, to be monitored without for­ward biasing the protection diodes in circuitry that may
have VCCcompletely removed.

The MAX3238 is available in a space-saving SSOP
package.

________________________Applications

Notebook, Subnotebook, and Palmtop
Computers

High-Speed Modems

Battery-Powered Equipment

Hand-Held Equipment

Peripherals

Printers

AutoShutdown Plus

i

s a trademark of Maxim Integrated Products.

*Patents Pending

____________________________Features

♦ 1µA Supply Current Achieved with

AutoShutdown Plus

♦ Guaranteed Data Rate: 250kbps

♦ 1µA Low-Power Shutdown

♦ Receivers Active in AutoShutdown Plus Mode

♦ Flow-Through Pinout

♦ Meets EIA/TIA-232 Specifications Down to 3.0V

♦ Guaranteed 6V/µs Slew Rate

MAX3238*

+3.0V to +5.5V, 1µA, up to 250kbps, True

RS-232 Transceiver with AutoShutdown Plus

________________________________________________________________ Maxim Integrated Products 1

__________________Pin Configuration

19-1144; Rev 1; 10/02

PART

MAX3238CAI

MAX3238EAI -40°C to +85°C

0°C to +70°C

TEMP RANGE PIN-PACKAGE

28 SSOP

28 SSOP

______________Ordering Information

Typical Operating Circuit appears at end of data sheet.

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.

TOP VIEW

C2+

GND

C2-

T1OUT

T2OUT

T3OUT

R1IN

R2IN

T4OUT

R3IN

T5OUT

FORCEON

FORCEOFF

1

2

3

V-

4

5

MAX3238

6

7

8

9

10

11

12

13

14

28

27

26

25

24

23

22

21

20

19

18

17

16

15

C1+

V+

V

CC

C1-

T1IN

T2IN

T3IN

R1OUT

R2OUT

T4IN

R3OUT

T5IN

R1OUTB

INVALID

SSOP

MAX3238

+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC= +3.0V to +5.5V; C1–C4 = 0.1µF (tested at 3.3V ±5%), C1–C4 = 0.22µF (tested at 3.3V ±10%), C1 = 0.047µF and
C2–C4 = 0.33µF (tested at 5.0V ±10%); T

A

= T

MIN

to T

MAX

; unless otherwise noted. Typical values are at 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.

VCC...........................................................................-0.3V to +6V

V+ (Note 1) ...............................................................-0.3V to +7V

V- (Note 1) ................................................................+0.3V to -7V

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

Input Voltages

T_IN, FORCEOFF, FORCEON ..............................-0.3V to +6V

R_IN .................................................................................±25V

Output Voltages

T_OUT...........................................................................±13.2V

R_OUT, INVALID ....................................-0.3V to (V

CC

+ 0.3V)

Short-Circuit Duration

T_OUT (one at a time) ............................................Continuous

Continuous Power Dissipation (T

A

= +70°C)

SSOP (derate 9.52mW/°C above +70°C) ....................762mW

Operating Temperature Ranges

MAX3238CAI ......................................................0°C to +70°C

MAX3238EAI....................................................-40°C to +85°C

Storage Temperature Range ............................-65°C to +160°C

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

FORCEOFF = GND, T

A

= +25°C

VCC= 3.3V or 5.0V, TA= +25°C, receivers idle,
transmitters idle, FORCEON = GND,
FORCEOFF = V

CC

I

OUT

= -1.0mA

I

OUT

= 1.6mA

Receivers disabled

T_IN, FORCEON, FORCEOFF

FORCEON = FORCEOFF = VCC, no load

T_IN, FORCEON, FORCEOFF

VCC= 3.3V

CONDITIONS

µA

1.0 10

Supply Current, Shutdown

µA

1.0 10

Supply Current, AutoShutdown Plus

V

V

CC

-V

CC

-

0.6 0.1

Output Voltage High

V0.4Output Voltage Low

µA±0.05 ±10Output Leakage Current

µA±0.01 ±1.0Input Leakage Current

mA0.5 2.0

Supply Current, AutoShutdown Plus
Disabled

V0.8Input Logic Threshold Low

V

2.0

Input Logic Threshold High

UNITSMIN TYP MAXPARAMETER

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

VCC= 5.0V 2.4

V-25 25Input Voltage Range

VCC= 3.3V 0.6 1.2

VCC= 5.0V

V

0.8 1.5

Input Threshold Low

VCC= 3.3V 1.5 2.4

VCC= 5.0V

V

1.8 2.4

Input Threshold High

V0.3Input Hysteresis

TA= +25°C kΩ357Input Resistance

DC CHARACTERISTICS

LOGIC INPUTS AND RECEIVER OUTPUTS

RECEIVER INPUTS

MAX3238

+3.0V to +5.5V, 1µA, up to 250kbps, True

RS-232 Transceiver with AutoShutdown Plus

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VCC= +3.0V to +5.5V; C1–C4 = 0.1µF (tested at 3.3V ±5%), C1–C4 = 0.22µF (tested at 3.3V ±10%), C1 = 0.047µF and
C2–C4 = 0.33µF (tested at 5.0V ±10%); T

A

= T

MIN

to T

MAX

; unless otherwise noted. Typical values are at TA= +25°C.)

Figure 4a

Figure 7a

Figure 4b (Note 2)

VCC= 5V, Figure 4b (Note 2)

VCC= 5V, Figure 4b

I

OUT

= 1.6mA

I

OUT

= -1.0mA

VCC= 5V, Figure 4b

CONDITIONS

V-0.3 0.3

Receiver Input Threshold to
INVALID Output Low

V

2.7

Receiver Input Threshold to
INVALID Output High

sec15 30 60

Receiver or Transmitter Edge to
Shutdown (t

AUTOSHDN

)

µs25

Receiver or Transmitter Edge to
Transmitters Enabled (t

WU

)

µs50

Receiver Positive or Negative
Threshold to INVALID Low (t

INVL

)

V0.4

INVALID Output Voltage Low

V

V

CC -

0.6

INVALID Output Voltage High

µs0.1

Receiver Positive or Negative
Threshold to INVALID High (t

INVH

)

UNITSMIN TYP MAXPARAMETER

Positive threshold

Negative threshold -2.7

Output Voltage Swing All transmitter outputs loaded with 3kΩ to ground ±5.0 ±5.4 V

Output Resistance VCC= V+ = V- = GND, T

OUT

= 2V 300 10M Ω

VCC≤ 3.6V ±35 ±60

Output Leakage Current

V

OUT

= ±12V, VCC= 0V to 5.5V,

transmitters disabled

±25 µA

| t

PHL

- t

PLH

|

430

t

PHL

R_IN to R_OUT,
C

L

= 150pF

t

PLH

CL= 150pF to 1000pF

RL= 3kΩ, CL= 1000pF, one transmitter switching

CL= 150pF to 2500pF

0.15

VCC= 3.3V,
TA= +25°C,
R

L

= 3Ω to 7kΩ,

measured from +3V to

-3V or -3V to +3V

Normal operation

Normal operation

| t

PHL

- t

PLH

|

µs

0.15

Receiver Propagation Delay

kbps250Maximum Data Rate

V/µs

630

Transition-Region Slew Rate

ns200Receiver Output Enable Time

ns200Receiver Output Disable Time

ns100Transmitter Skew

ns50Receiver Skew

TIMING CHARACTERISTICS

Output Short-Circuit Current

VCC> 3.6V ±40 ±100

AutoShutdown (FORCEON = GND, FORCEOFF = VCC)

TRANSMITTER OUTPUTS

Note 2: A transmitter/receiver edge is defined as a transition through the transmitter/receiver input logic thresholds.

mA

______________________________________________________________Pin Description

7.5

-5.0

-7.5
0 1000 3000 5000

TRANSMITTER OUTPUT VOLTAGE

vs. LOAD CAPACITANCE

-2.5

5.0

MAX3238 TOC-01

LOAD CAPACITANCE (pF)

TRANSMITTER OUTPUT VOLTAGE (V)

2000 4000

2.5

0

V

OUT

+

V

OUT

–

FOR DATA RATES UP TO 250kbps
1 TRANSMITTER 250kbps
4 TRANSMITTERS 15.6kbps
LOADED 3kΩ + C

L

14

4

2

0

0 1000 3000 5000

SLEW RATE

vs. LOAD CAPACITANCE

6

12

MAX3238-02

SLEW RATE (V/µs)

LOAD CAPACITANCE (pF)

2000 4000

10

8

+SLEW

–SLEW

1 TRANSMITTER 250kbps
4 TRANSMITTERS 15.6kbps
LOADED 3kΩ + C

L

70

20

10

0

0 1000 3000 5000

SUPPLY CURRENT vs. LOAD CAPACITANCE

WHEN TRANSMITTING DATA

30

60

MAX3238 TOC-03

SUPPLY CURRENT (mA)

LOAD CAPACITANCE (pF)

2000 4000

50

40

250kbps

120kbps

20kbps

__________________________________________Typical Operating Characteristics

(VCC= +3.3V, 250kbps data rate, 0.1µF capacitors, all transmitters loaded with 3kΩ, TA= +25°C, unless otherwise noted.)

MAX3238

+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus

4 _______________________________________________________________________________________

Positive Terminal of Voltage-Doubler Charge-Pump CapacitorC1+28

+5.5V Generated by the Charge PumpV+27

+3.0V to +5.5V Supply VoltageV

CC

26

NAME FUNCTION

1

C2+ Positive Terminal of Inverting Charge-Pump Capacitor

2 GND Ground

PIN

3 C2- Negative Terminal of Inverting Charge-Pump Capacitor

4 V- -5.5V Generated by the Charge Pump

14

FORCEOFF

Force-Off Input. Drive low to shut down transmitters, receivers (except R1OUTB), and on­board supply. This overrides AutoShutdown Plus and FORCEON (Table 1).

13 FORCEON

Force-Off Input. Drive high to override AutoShutdown Plus, keeping transmitters and
receivers on (FORCEOFF must be high) (Table 1).

8, 9, 11 R_IN RS-232 Receiver Inputs (R1IN–R3IN)

5, 6, 7, 10, 12 T_OUT RS-232 Transmitter Outputs (T1OUT–T5OUT)

25 C1- Negative Terminal of Voltage-Doubler Charge-Pump Capacitor

18, 20, 21 R_OUT TTL/CMOS Receiver Outputs (R3OUT–R1OUT)

17, 19, 22, 23, 24 T_IN TTL/CMOS Transmitter Inputs (T5IN–T1IN)

16 R1OUTB Noninverting Complementary Receiver Output. Always active.

15

INVALID

Output of the Valid Signal Detector. A logic “1” indicates if a valid RS-232 level is present
on receiver inputs.