Maxim MAX3238CAI, MAX3238EAI Datasheet

19-1144; Rev 0; 9/96

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

RS-232 Transceiver with AutoShutdown Plus™

_______________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

Typical Operating Circuit appears at end of data sheet.

AutoShutdown Plus is 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

______________Ordering Information

PART

MAX3238CAI
MAX3238EAI -40°C to +85°C

TEMP. RANGE PIN-PACKAGE

0°C to +70°C

28 SSOP
28 SSOP

__________________Pin Configuration

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

SSOP

28
27
26
25
24
23
22
21
20
19
18
17
16
15

C1+
V+

V

CC

C1­T1IN
T2IN
T3IN

R1OUT
R2OUT

T4IN
R3OUT
T5IN
R1OUTB
INVALID

MAX3238*

________________________________________________________________

Maxim Integrated Products

1

For free samples & the latest literature: http://www.maxim-ic.com, or phone [phone]

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

ABSOLUTE MAXIMUM RATINGS

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

MAX3238

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

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

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.

CC

+ 0.3V)

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

DC CHARACTERISTICS

Supply Current, AutoShutdown Plus

Supply Current, Shutdown

= T

to T

A

MIN

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

FORCEOFF = V
FORCEOFF = GND, T

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

MAX

CONDITIONS

CC

Short-Circuit Duration

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

Continuous Power Dissipation (TA= +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, 10sec) ............................+300°C

1.0 10

= +25°C

A

1.0 10

UNITSMIN TYP MAXPARAMETER

µA

µA

Supply Current, AutoShutdown Plus
Disabled

LOGIC INPUTS AND RECEIVER OUTPUTS

Input Logic Threshold High

Output Voltage High

RECEIVER INPUTS

Input Threshold Low

Input Threshold High

2 _______________________________________________________________________________________

FORCEON = FORCEOFF = VCC, no load

T_IN, FORCEON, FORCEOFF
VCC= 3.3V
VCC= 5.0V 2.4
T_IN, FORCEON, FORCEOFF
Receivers disabled
I

= 1.6mA

OUT

I

= -1.0mA

OUT

VCC= 3.3V 0.6 1.2
VCC= 5.0V
VCC= 3.3V 1.5 2.4
VCC= 5.0V

TA= +25°C kΩ357Input Resistance

2.0

V

-V

CC

0.6 0.1

0.8 1.5

CC

1.8 2.4

mA0.5 2.0

V0.8Input Logic Threshold Low

V

µA±0.01 ±1.0Input Leakage Current
µA±0.05 ±10Output Leakage Current

V0.4Output Voltage Low

­V

V-25 25Input Voltage Range
V

V
V0.3Input Hysteresis

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

RS-232 Transceiver with AutoShutdown Plus™

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

AutoShutdown (FORCEON = GND, FORCEOFF = VCC)
Receiver Input Threshold to

INVALID Output High
Receiver Input Threshold to

INVALID Output Low
INVALID Output Voltage Low

INVALID Output Voltage High

Receiver Positive or Negative
Threshold to INVALID High (t

Receiver Positive or Negative
Threshold to INVALID Low (t

Receiver or Transmitter Edge to
Transmitters Enabled (tWU)

Receiver or Transmitter Edge to
Shutdown (t

TRANSMITTER OUTPUTS

Output Voltage Swing All transmitter outputs loaded with 3kΩ to ground ±5.0 ±5.4 V
Output Resistance VCC= V+ = V- = GND, T

Output Short-Circuit Current

Output Leakage Current

TIMING CHARACTERISTICS

Receiver Propagation Delay

Transition-Region Slew Rate

AUTOSHDN

)

INVH

INVL

)

)

= T

to T

A

MIN

Figure 7a

Figure 4a

I

= 1.6mA

OUT

I

= -1.0mA

OUT

VCC= 5V, Figure 4b

VCC= 5V, Figure 4b

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

Figure 4b (Note 2)

VCC≤ 3.6V ±35 ±60
VCC> 3.6V ±40 ±100
V

= ±12V, VCC= 0V to 5.5V,

OUT

transmitters disabled

RL= 3kΩ, CL= 1000pF, one transmitter switching
R_IN to R_OUT,

CL= 150pF
Normal operation

Normal operation
| t

- t

PHL

PLH

| t

- t

PHL

PLH

VCC= 3.3V,
TA= +25°C,
RL= 3Ω to 7kΩ,
measured from +3V to

-3V or -3V to +3V

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

MAX

CONDITIONS

Positive threshold
Negative threshold -2.7

V

CC -

0.6

= 2V 300 10M Ω

OUT

t

PHL

t

PLH

|
|

CL= 150pF to 1000pF

CL= 150pF to 2500pF

630

430

2.7

±25 µA

0.15

0.15

UNITSMIN TYP MAXPARAMETER

V

V-0.3 0.3

V0.4

V

µs0.1

µs50

µs25

sec15 30 60

mA

kbps250Maximum Data Rate

µs

ns200Receiver Output Enable Time
ns200Receiver Output Disable Time
ns100Transmitter Skew
ns50Receiver Skew

V/µs

MAX3238

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

_______________________________________________________________________________________ 3

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

__________________________________________Typical Operating Characteristics

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

TRANSMITTER OUTPUT VOLTAGE

vs. LOAD CAPACITANCE

7.5

5.0

2.5

MAX3238

0

-2.5

-5.0

TRANSMITTER OUTPUT VOLTAGE (V)

-7.5



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

0 1000 3000 5000

2000 4000

LOAD CAPACITANCE (pF)

MAX3238 TOC-01

SLEW RATE (V/µs)

14

12

+SLEW

10

8



1 TRANSMITTER 250kbps

6

4 TRANSMITTERS 15.6kbps
LOADED 3kΩ + C

4

2

0

0 1000 3000 5000

V

+

OUT



L

V

–

OUT

SLEW RATE

vs. LOAD CAPACITANCE

–SLEW



L

2000 4000

LOAD CAPACITANCE (pF)

MAX3238-02

______________________________________________________________Pin Description

SUPPLY CURRENT vs. LOAD CAPACITANCE

WHEN TRANSMITTING DATA

70

60

50

40
30

20

SUPPLY CURRENT (mA)

10

0

0 1000 3000 5000

250kbps

120kbps

2000 4000

LOAD CAPACITANCE (pF)

20kbps

MAX3238 TOC-03

PIN

1

NAME FUNCTION

C2+ Positive Terminal of Inverting Charge-Pump Capacitor
2 GND Ground
3 C2- Negative Terminal of Inverting Charge-Pump Capacitor
4 V- -5.5V Generated by the Charge Pump

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

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

13 FORCEON

14

15

FORCEOFF

INVALID

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

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

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

16 R1OUTB Noninverting Complementary Receiver Output. Always active.

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

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

25 C1- Negative Terminal of Voltage-Doubler Charge-Pump Capacitor
26

CC

+3.0V to +5.5V Supply VoltageV
+5.5V Generated by the Charge PumpV+27
Positive Terminal of Voltage-Doubler Charge-Pump CapacitorC1+28

4 _______________________________________________________________________________________