_______________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 con-
nected 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 communica-
tions 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 popu-
lar software for communicating with personal comput-
ers. 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 addi-
tion to its standard output), which allows external
devices, such as a modem, to be monitored without for-
ward biasing the protection diodes in circuitry that may
have VCC completely 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.
*P
____________________________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
28
27
26
25
24
23
22
21
20
19
18
17
16
15
1
2
3
4
5
6
7
8
9
10
11
12
13
14
C1+
V+
VCC
C1-
T1IN
T2IN
INVALID
T3IN
R1OUT
R2OUT
T4IN
R3OUT
T5IN
R1OUTB
FORCEOFF
FORCEON
T5OUT
R3IN
T4OUT
R2IN
R1IN
T3OUT
T2OUT
T1OUT
V-
C2-
GND
C2+
SSOP
TOP VIEW
MAX3238
__________________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.
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%); TA= TMIN to TMAX; 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 (VCC + 0.3V)
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, 10s) ................................+300°C
FORCEOFF = GND, TA= +25°C
VCC = 3.3V or 5.0V, TA= +25°C, receivers idle,
transmitters idle, FORCEON = GND,
FORCEOFF = VCC
IOUT = -1.0mA
IOUT = 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
VCC -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%); TA= TMIN to TMAX; 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
IOUT = 1.6mA
IOUT = -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 (tAUTOSHDN)
µs25
Receiver or Transmitter Edge to
Transmitters Enabled (tWU)
µs50
Receiver Positive or Negative
Threshold to INVALID Low (tINVL)
V0.4
INVALID Output Voltage Low
V
VCC -
0.6
INVALID Output Voltage High
µs0.1
Receiver Positive or Negative
Threshold to INVALID High (tINVH)
UNITSMIN TYP MAXPARAMETER
Positive threshold
Negative threshold -2.7
Output Voltage Swing All transmitter outputs loaded with 3kΩto ground ±5.0 ±5.4 V
Output Resistance VCC = V+ = V- = GND, TOUT = 2V 300 10M Ω
VCC ≤3.6V ±35 ±60
Output Leakage Current VOUT = ±12V, VCC = 0V to 5.5V,
transmitters disabled ±25 µA
| tPHL - tPLH |
430
tPHL
R_IN to R_OUT,
CL= 150pF tPLH
CL= 150pF to 1000pF
RL= 3kΩ, CL= 1000pF, one transmitter switching
CL= 150pF to 2500pF
0.15
VCC = 3.3V,
TA= +25°C,
RL= 3Ωto 7kΩ,
measured from +3V to
-3V or -3V to +3V
Normal operation
Normal operation
| tPHL - tPLH |
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
VOUT+
VOUT–
FOR DATA RATES UP TO 250kbps
1 TRANSMITTER 250kbps
4 TRANSMITTERS 15.6kbps
LOADED 3kΩ + CL
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 + CL
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 VoltageVCC
26
NAME FUNCTION
1C2+ Positive Terminal of Inverting Charge-Pump Capacitor
2GND Ground
PIN
3C2- Negative Terminal of Inverting Charge-Pump Capacitor
4V- -5.5V Generated by the Charge Pump
14 FORCEOFF Force-Off Input. Drive low to shut down transmitters, receivers (except R1OUTB), and on-
board 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.
MAX3238
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus
_______________________________________________________________________________________ 5
_______________Detailed Description
Dual Charge-Pump Voltage Converter
The MAX3238’s internal power supply consists of a reg-
ulated dual charge pump that provides output voltages
of +5.5V (doubling charge pump) and -5.5V (inverting
charge pump), regardless of the input voltage (VCC)
over the 3.0V to 5.5V range. 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.
Each charge pump requires a flying capacitor (C1, C2)
and a reservoir capacitor (C3, C4) to generate the V+
and V- supplies.
RS-232 Transmitters
The transmitters are inverting level translators that con-
vert CMOS-logic levels to 5.0V EIA/TIA-232 levels. The
MAX3238 transmitters guarantee a 250kbps data rate
with worst-case loads of 3kΩin parallel with 1000pF,
providing compatibility with PC-to-PC communication
software (such as LapLink™). Transmitters can be par-
alleled to drive multiple receivers. Figure 1 shows a
complete system connection.
LapLink is a trademark of Traveling Software.
When FORCEOFF is driven to ground, the transmitters
and receivers are disabled and the outputs go high
impedance, except for R1OUTB. When the Auto-
Shutdown Plus circuitry senses that all receiver and
transmitter inputs are inactive for more than 30sec, the
transmitters are disabled and the outputs go into a
high-impedance state, but the receivers remain active.
When the power is off, the MAX3238 permits the out-
puts to be driven up to ±12V.
The transmitter inputs do not have pull-up resistors.
Connect unused inputs to GND or VCC.
RS-232 Receivers
The receivers convert RS-232 signals to CMOS-logic
output levels. All receivers have inverting three-state
outputs and are inactive in shutdown (FORCEOFF)
(Table 1). The MAX3238 also features an extra, always-
active noninverting output, R1OUTB. This extra output
monitors receiver activity while the other receivers are
high impedance, allowing Ring Indicator to be moni-
tored without forward biasing other devices connected
to the receiver outputs. This is ideal for systems where
VCC is set to 0V in shutdown to accommodate peripher-
als, such as UARTs (Figure 2).
Table 1. Output Control Truth Table
FORCEON FFOORRCCEEOOFFFFAUTOSHUTDOWN
PLUS*
OPERATION
STATUS T_OUT R_OUT R1OUTB
X 0 X Shutdown
(Forced Off) High-Z High-Z Active
1 1 X Normal Operation
(Forced On) Active Active Active
0 1 <30sec*
Normal
Operation
(AutoShutdown
Plus)
Active Active Active
0 1 >30sec*
Shutdown
(AutoShutdown
Plus)
High-Z Active Active
X= Don’t Care
*Time since last receiver or transmitter input transition.
MAX3238
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus
6 _______________________________________________________________________________________
AutoShutdown Plus Mode
1µA supply current is achieved with Maxim’s
AutoShutdown Plus feature, which operates when
FORCEOFF is high and FORCEON is low. When the
MAX3238 senses no valid signal transitions on all
receiver and transmitter inputs for 30sec, the on-board
power supply and drivers are shut off, reducing supply
current to 1µA. This occurs if the RS-232 cable is dis-
connected or if the connected peripheral transmitters
are turned off. The system turns on again when a valid
transition is applied to any RS-232 receiver or transmit-
ter input. As a result, the system saves power without
changes to the existing BIOS or operating system. The
INVALID output is high when the receivers are active.
Since INVALID indicates the receiver inputs’ condition,
it can be used in any mode (Figure 3).
MAX3238
I/O
CHIP
WITH
UART
CPU
RS-232
POWER
MANAGEMENT
UNIT OR
KEYBOARD
CONTROLLER
FORCEOFF
FORCEON
INVALID
T1
T2
T3
T4
T5
R1
R2
R3
Figure 1. Interface Under Control of PMU
MAX3238
T1OUT
R1OUTB
Tx
5kΩ
UART
VCC
T1IN
THREE-STATED
LOGIC
TRANSITION
DETECTOR
R1IN
PROTECTION
DIODE
R1OUT
FORCEOFF = GND
VCC
TO
µP
Rx
PREVIOUS
RS-232
Tx
UART
SHDN = GND
VCC
VCC
GND
Rx
5kΩ
(a) OLDER RS-232: POWERED-DOWN UART DRAWS CURRENT FROM ACTIVE
RECEIVER OUTPUT IN SHUTDOWN.
(b) NEW MAX3238: IN SHUTDOWN, R1OUTB IS USED TO MONITOR EXTERNAL
DEVICES AND R1OUT IS THREE STATED, ELIMINATING A CURRENT PATH
THROUGH THE UART'S PROTECTION DIODE.
GND
PROTECTION
DIODE
I
I
Figure 2. The MAX3238 detects RS-232 activity when the
UART and interface are shut down.
MAX3238
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus
_______________________________________________________________________________________ 7
Tables 1 and 2 and Figure 3 summarize the MAX3238’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.
When shut down, the device’s charge pumps turn off,
V+ decays to VCC, V- decays to ground, and the trans-
mitter outputs are disabled (high impedance). The time
required to exit shutdown is typically 25µs (Figure 4b).
Software-Controlled Shutdown
If direct software control is desired, use INVALID to
indicate DTR or Ring Indicator signal. Tie FORCEOFF
and FORCEON together to bypass the AutoShutdown
feature so the line acts like a SHDN input.
__________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 3 for required capacitor values. Do not use val-
ues smaller than those listed in Table 3. 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 CBYPASS,to maintain the proper ratios (C1 to the
other capacitors).
Table 2. IINNVVAALLIIDDTruth Table
+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
R
+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.
30µs
TIMER
R
AUTOSHDN
R_IN
T_IN
R
S
30sec
TIMER
EDGE
DETECT
EDGE
DETECT
FORCEOFF
FORCEON
Figure 3a.
INVALID
Functional Diagram,
INVALID
Low
Figure 3b.
INVALID
Functional Diagram,
INVALID
High
Figure 3c. AutoShutdown Plus Logic
POWERDOWN*
AUTOSHDN
FORCEOFF
FORCEON
* POWERDOWN IS ONLY AN INTERNAL SIGNAL.
IT CONTROLS THE OPERATIONAL STATUS OF
THE TRANSMITTERS AND THE POWER SUPPLIES.
Figure 3d. Power-Down Logic
L
No
HYes
IINNVVAALLIIDDOUTPUT
RS-232 SIGNAL PRESENT AT
ANY RECEIVER INPUT
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 larger nominal value. The capacitor’s equiv-
alent series resistance (ESR), which usually rises at low
temperatures, influences the amount of ripple on V+
and V-.
MAX3238
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus
8 _______________________________________________________________________________________
Table 3. Required Minimum Capacitance
Values
RECEIVER INPUT LEVELS
-2.7V
-0.3V
+2.7V
+0.3V
0V
INDETERMINATE
INVALID HIGH
INVALID LOW
INVALID HIGH
INDETERMINATE
Figure 4a. Receiver Positive/Negative Thresholds for
INVALID
VCC
0
V+
V-
VCC
0
INVALID
OUTPUT
* ALL RECEIVERS/TRANSMITTERS INACTIVE
** ANY ONE RECEIVER/TRANSMITTER BECOMES ACTIVE FORCEON = GND, FORCEOFF = VCC
TRANSMITTER
INPUTS
VOLTAGE
RECEIVER
INPUTS
VOLTAGE
TRANSMITTER
OUTPUTS
VOLTAGE
tAUTOSHDN
INVALID
REGION
***
tWU tWU
INVL
tAUTOSHDN
Figure 4b. AutoShutdown Plus and
INVALID
Timing Diagram
10.223.0 to 5.5
0.330.0474.5 to 5.5
C2, C3, C4, CBYPASS
(µF)
0.22
0.10.13.15 to 3.6
0.223.0 to 3.6
C1
(µF)
VCC
(V)
Power-Supply Decoupling
In applications that are sensitive to power-supply noise,
decouple VCC to ground with a capacitor of the same
value as capacitors C2, C3, and C4. Connect the
bypass capacitor as close to the IC as possible.
Transmitter Outputs when
Exiting Shutdown
Figure 5 shows two transmitter outputs when exiting
shutdown mode. As they become active, the outputs
are shown going to opposite RS-232 levels (one trans-
mitter input is high, the other is low). Each transmitter is
loaded with 3kΩin parallel with 2500pF. 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 MAX3238 maintains the RS-232 ±5.0V minimum
transmitter output voltage even at high data rates.
Figure 6 shows a transmitter loopback test circuit.
Figure 7 shows a loopback test result at 120kbps, and
Figure 8 shows the same test at 250kbps. For Figure 7,
all transmitters were driven simultaneously at 120kbps
into RS-232 loads in parallel with 1000pF. For Figure 8,
a single transmitter was driven at 250kbps, and all
transmitters were loaded with an RS-232 receiver in
parallel with 1000pF.
Interconnection
with 3V and 5V Logic
The MAX3238 can directly interface with various 5V-
logic families, including ACT and HCT CMOS. See
Table 4 for more information on possible combinations
of interconnections.
MAX3238
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus
_______________________________________________________________________________________ 9
VCC = 3.3V
C1 - C4 = 0.1µF
5µs/div
2V/div
2V/div
T2OUT
T1OUT
FORCEON =
FORCEOFF
Figure 5. Transmitter Outputs when Exiting Shutdown or
Powering Up
Table 4. Logic Family Compatibility with
Various Supply Voltages
SYSTEM
POWER-
SUPPLY
VOLTAGE
(V)
VCC
SUPPLY
VOLTAGE
(V)
COMPATIBILITY
3.3 3.3 Compatible with all CMOS families.
5 5 Compatible with all TTL and CMOS
families.
53.3
Compatible with ACT and HCT
CMOS, and with AC, HC, or
CD4000 CMOS.
MAX3238
5kΩ
R_ IN
R_ OUT
C2-
C2+
C1-
C1+
V-
V+
VCC
C4
C3*
C1
C2
VCC
FORCEOFF
T_ OUT
T_ IN
GND
VCC
*C3 CAN BE RETURNED TO VCC OR GND.
FORCEON 1000pF
Figure 6. Loopback Test Circuit
MAX3238
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus
10 ______________________________________________________________________________________
VCC = 3.3V
C1 - C4 = 0.1µF
CLOAD = 1000pF
2µs/div
T1IN
T1OUT
R1OUT
5V
0V
0V
0V
+5V
5V
-5V
Figure 8. Loopback Test Result at 250kbps
VCC = 3.3V
C1 - C4 = 0.1µF
CLOAD = 1000pF
2µs/div
T1IN
T1OUT
R1OUT
0V
0V
0V
5V
+5V
5V
-5V
Figure 7. Loopback Test Result at 120kbps
___________________Chip Information
TRANSISTOR COUNT: 1404
MAX3238
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus
______________________________________________________________________________________ 11
MAX3238
RS-232
OUTPUTS
LOGIC
INPUTS
RS-232
INPUTS
LOGIC
OUTPUTS
*C3 MAY BE RETURNED TO EITHER VCC OR GND.
FORCEOFF
INVALID
AUTOSHUTDOWN PLUS
FORCEON
T1IN T1OUT
T2IN T2OUT
T3IN T3OUT
T4IN T4OUT
T5IN
5
6
7
10
12T5OUT
15
24
23
22
19
C1+ VCC V+
C1-
C2+ V-
C2-
27 *
26
4
28
0.1µF
0.1µF
0.1µF
0.1µF
25
1
3
17
R1OUTB16
R1OUT 8R1IN21
R2OUT 9R2IN20
R3OUT 11
5kΩ
5kΩ
5kΩ
GND
2
R3IN18
14
13
T1
T2
T3
T4
T5
R1
R2
R3
0.1µF
__________Typical Operating Circuit
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.
12 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600
© 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
MAX3238
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus
L
DIM
A
A1
B
C
D
E
e
H
L
α
DIM
D
D
D
D
D
MIN
0.068
0.002
0.010
0.004
0.205
0.301
0.025
0˚
MIN
0.239
0.239
0.278
0.317
0.397
MAX
0.078
0.008
0.015
0.008
0.209
0.311
0.037
8˚
MAX
0.249
0.249
0.289
0.328
0.407
MIN
1.73
0.05
0.25
0.09
5.20
7.65
0.63
0˚
MIN
6.07
6.07
7.07
8.07
10.07
MAX
1.99
0.21
0.38
0.20
5.38
7.90
0.95
8˚
PINS
14
16
20
24
28
MAX
6.33
6.33
7.33
8.33
10.33
INCHES
INCHES
MILLIMETERS
MILLIMETERS
α
SSOP
SHRINK
SMALL-OUTLINE
PACKAGE
HE
D
A
A1
C
B
0.65 BSC0.0256 BSC
21-0056A
e
SEE VARIATIONS
Package Information
(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.)
