Page 1
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 1-800-998-8800
Page 2
+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
Page 3
+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
Page 4
+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 _______________________________________________________________________________________
Page 5
+3.0V to +5.5V, 1µA, up to 250kbps, True
FORCEOFF
RS-232 Transceiver with AutoShutdown Plus™
Table 1. Output Control Truth Table
FORCEON
X 0 X
1 1 X
0 1 <30sec*
0 1 >30sec*
X = Don’t Care
* Time since last receiver or transmitter input transition.
AUTOSHUTDOWN
PLUS*
OPERATION
Shutdown
(Forced Off)
Normal Operation
(Forced On)
Normal
Operation
(AutoShutdown
Plus)
Shutdown
(AutoShutdown
Plus)
_______________Detailed Description
Dual Charge-Pump Voltage Converter
The MAX3238’s internal power supply consists of a regulated 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 convert CMOS-logic levels to 5.0V EIA/TIA-232 levels. The
MAX3238 transmitters guarantee a 250kbps data rate
with worst-case loads of 3kΩ in parallel with 1000pF,
providing compatibility with PC-to-PC communication
software (such as LapLink™). Transmitters can be paralleled to drive multiple receivers. Figure 1 shows a
complete system connection.
STATUS
When FORCEOFF is driven to ground, the transmitters
and receivers are disabled and the outputs go high
impedance, except for R1OUTB. When the AutoShutdown 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 outputs to be driven up to ±12V.
The transmitter inputs do not have pull-up resistors.
Connect unused inputs to GND or VCC.
T_OUT R_OUT R1OUTB
High-Z High-Z Active
Active Active Active
Active Active Active
High-Z Active Active
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, alwaysactive noninverting output, R1OUTB. This extra output
monitors receiver activity while the other receivers are
high impedance, allowing Ring Indicator to be monitored without forward biasing other devices connected
to the receiver outputs. This is ideal for systems where
VCCis set to 0V in shutdown to accommodate peripherals, such as UARTs (Figure 2).
MAX3238
LapLink is a trademark of Traveling Software.
_______________________________________________________________________________________ 5
Page 6
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus™
V
SHDN = GND
LOGIC
CC
PREVIOUS
RS-232
I
5k
V
CC
POWER
MANAGEMENT
UNIT OR
KEYBOARD
CONTROLLER
FORCEOFF
FORCEON
INVALID
MAX3238
I/O
CPU
CHIP
WITH
UART
MAX3238
T1
T2
T3
T4
T5
R1
R2
R3
RS-232
PROTECTION
DIODE
V
CC
Rx
UART
Tx
GND
(a) OLDER RS-232: POWERED-DOWN UART DRAWS CURRENT FROM ACTIVE
RECEIVER OUTPUT IN SHUTDOWN.
TO
µP
TRANSITION
DETECTOR
I
PROTECTION
Figure 1. Interface Under Control of PMU
AutoShutdown Plus Mode
1µA supply current is achieved with Maxim’s
AutoShutdown Plus feature, which operates when
FORCEOFF is low and FORCEON is high. 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-
DIODE
V
CC
Rx
UART
Tx
GND
R1OUTB
R1OUT
THREE-STATED
T1IN
FORCEOFF = GND
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 transmitter input. As a result, the system saves power without
changes to the existing BIOS or operating system. The
(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.
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).
6 _______________________________________________________________________________________
Figure 2. The MAX3238 detects RS-232 activity when the
UART and interface are shut down.
MAX3238
R1IN
5k
T1OUT
Page 7
+3.0V to +5.5V, 1µA, up to 250kbps, True
INVALID
INVALID
RS-232 Transceiver with AutoShutdown Plus™
Table 2.
Truth Table
RS-232 SIGNAL PRESENT AT
ANY RECEIVER INPUT
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 V
V- decays to ground, and the trans-
CC,
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.
OUTPUT
HYes
LNo
__________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 3 for required capacitor values. Do not use values 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 C
BYPASS
other capacitors).
, to maintain the proper ratios (C1 to the
+0.3V
R_IN
-0.3V
INVALID ASSERTED IF ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR
AT LEAST 30µs.
Figure 3a. INVALID Functional Diagram, INVALID Low
+2.7V
R_IN
-2.7V
INVALID DEASSERTED IF ANY RECEIVER INPUT HAS BEEN BETWEEN +2.7V AND -2.7V
FOR LESS THAN 30µs.
Figure 3b. INVALID Functional Diagram, INVALID High
T_IN
R_IN
Figure 3c. AutoShutdown Plus Logic
AUTOSHDN
* POWERDOWN IS ONLY AN INTERNAL SIGNAL.
IT CONTROLS THE OPERATIONAL STATUS OF
THE TRANSMITTERS AND THE POWER SUPPLIES.
EDGE
DETECT
EDGE
DETECT
FORCEON
FORCEOFF
FORCEON
30µs
TIMER
30µs
TIMER
FORCEOFF
S
30sec
TIMER
R
INVALID
R
INVALID
R
AUTOSHDN
POWERDOWN*
MAX3238
Figure 3d. Power-Down Logic
_______________________________________________________________________________________ 7
Page 8
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus™
When using the minimum required capacitor values,
make sure the capacitor value does not degrade
excessively with temperature. If in doubt, use capaci-
INVALID HIGH
+2.7V
INDETERMINATE
tors with a larger nominal value. The capacitor’s equivalent series resistance (ESR), which usually rises at low
temperatures, influences the amount of ripple on V+
and V-.
+0.3V
MAX3238
0V
-0.3V
RECEIVER INPUT LEVELS
-2.7V
INVALID LOW
INDETERMINATE
INVALID HIGH
Figure 4a. Receiver Positive/Negative Thresholds for INVALID
INVALID
REGION
RECEIVER
INPUTS
VOLTAGE
TRANSMITTER
INPUTS
VOLTAGE
TRANSMITTER
OUTPUTS
VOLTAGE
***
Table 3. Required Minimum Capacitance
Values
V
(V)
CC
C1
(µF)
0.223.0 to 3.6
C2, C3, C4, C
(µF)
0.22
0.10.13.15 to 3.6
0.330.0474.5 to 5.5
10.223.0 to 5.5
BYPASS
V
INVALID
OUTPUT
* ALL RECEIVERS/TRANSMITTERS INACTIVE
** ANY ONE RECEIVER/TRANSMITTER BECOMES ACTIVE FORCEON = GND, FORCEOFF = V
CC
0
I
NVL
V+
V
CC
0
V-
t
AUTOSHDN
t
WU
t
AUTOSHDN
t
WU
Figure 4b. AutoShutdown Plus and INVALID Timing Diagram
8 _______________________________________________________________________________________
CC
Page 9
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus™
Power-Supply Decoupling
In applications that are sensitive to power-supply noise,
decouple VCCto 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 transmitter input is high, the other is low). Each transmitter is
loaded with 3kΩ in 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 5Vlogic families, including ACT and HCT CMOS. See
Table 4 for more information on possible combinations
of interconnections.
Table 4. Logic Family Compatibility with
Various Supply Voltages
SYSTEM
POWER-
SUPPLY
VOLTAGE
(V)
3.3 3.3 Compatible with all CMOS families.
5 5
5 3.3
V
CC
V
CC
SUPPLY
VOLTAGE
(V)
COMPATIBILITY
Compatible with all TTL and CMOS
families.
Compatible with ACT and HCT
CMOS, and with AC, HC, or
CD4000 CMOS.
MAX3238
FORCEON =
2V/div
2V/div
VCC = 3.3V
C1 - C4 = 0.1µF
Figure 5. Transmitter Outputs when Exiting Shutdown or
Powering Up
5µs/div
_______________________________________________________________________________________ 9
FORCEOFF
T2OUT
T1OUT
C1+
C1
C2
V
CC
*C3 CAN BE RETURNED TO VCC OR GND.
Figure 6. Loopback Test Circuit
C1-
C2+
C2-
T_ IN
R_ OUT
FORCEON
FORCEOFF
V
MAX3238
GND
CC
V+
V-
T_ OUT
R_ IN
5k
C3*
C4
1000pF
Page 10
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus™
T1IN
MAX3238
T1OUT
R1OUT
VCC = 3.3V
C1 - C4 = 0.1µF
C
= 1000pF
LOAD
2µs/div
Figure 7. Loopback Test Result at 120kbps
+5V
-5V
5V
0V
0V
5V
0V
T1IN
T1OUT
R1OUT
VCC = 3.3V
C1 - C4 = 0.1µF
C
= 1000pF
LOAD
2µs/div
5V
0V
+5V
0V
-5V
5V
0V
Figure 8. Loopback Test Result at 250kbps
___________________Chip Information
TRANSISTOR COUNT: 1404
10 ______________________________________________________________________________________
Page 11
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus™
__________Typical Operating Circuit
0.1µF
26
V
CC
MAX3238
27
V+
*
0.1µF
4
0.1µF
0.1µF
0.1µF
C1+
28
C1-
25
C2+ V-
1
C2-
3
MAX3238
LOGIC
INPUTS
LOGIC
OUTPUTS
24
T1IN T1OUT
23
T2IN T2OUT
22
T3IN T3OUT
19
T4IN T4OUT
17
T5IN
14
FORCEOFF
13
FORCEON
R1OUTB16
R1OUT 8R1IN21
R2OUT 9R2IN20
AUTOSHUTDOWN PLUS
T1
T2
T3
T4
T5
R1
R2
INVALID
5k
5k
5
6
7
RS-232
OUTPUTS
10
12T5OUT
15
RS-232
INPUTS
R3OUT 11
*C3 MAY BE RETURNED TO EITHER V
R3
______________________________________________________________________________________ 11
GND
OR GND.
CC
R3IN18
5k
2
Page 12
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus™
________________________________________________________Package Information
MAX3238
DIM
A
A1
B
C
α
HE
C
L
D
E
e
H
L
α
INCHES
MIN
0.068
0.002
0.010
0.004
0.205
0.301
0.025
MAX
0.078
0.008
0.015
0.008
SEE VARIATIONS
0.209
0.311
0.037
0˚
8˚
MILLIMETERS
MIN
1.73
0.05
0.25
0.09
5.20
0.65 BSC0.0256 BSC
7.65
0.63
0˚
MAX
1.99
0.21
0.38
0.20
5.38
7.90
0.95
8˚
14
16
20
24
28
INCHES
MIN
0.239
0.239
0.278
0.317
0.397
DIM
PINS
e
SSOP
A
SHRINK
SMALL-OUTLINE
B
A1
PACKAGE
D
D
D
D
D
MAX
0.249
0.249
0.289
0.328
0.407
MILLIMETERS
MAX
MIN
6.33
6.07
6.33
6.07
7.33
7.07
8.33
8.07
10.33
10.07
21-0056A
D
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
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.
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
12
__________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600
© 1996 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
© 1996 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
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