Maxim MAX3238CAI-T 3.0v to 5.5v, 1î¼a, up to 250kbps, true rs-232 transceiver with autoshutdown plus Datasheet

19-1144; Rev 1; 10/02
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus
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 VCC completely removed.
The MAX3238 is available in a space-saving SSOP
package.
____________________________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
TEMP RANGE
PIN-PACKAGE
MAX3238CAI
0°C to +70°C
28 SSOP
MAX3238EAI
-40°C to +85°C
28 SSOP
__________________Pin Configuration
TOP VIEW
C2+
1
28 C1+
GND
2
27 V+
C2-
3
26 VCC
V-
4
25 C1-
High-Speed Modems
T1OUT
5
Battery-Powered Equipment
T2OUT
6
23 T2IN
Hand-Held Equipment
T3OUT
7
22 T3IN
R1IN
8
21 R1OUT
9
20 R2OUT
________________________Applications
Notebook, Subnotebook, and Palmtop
Computers
Peripherals
R2IN
Printers
24 T1IN
MAX3238
19 T4IN
T4OUT 10
18 R3OUT
R3IN 11
Typical Operating Circuit appears at end of data sheet.
AutoShutdown Plus is a trademark of Maxim Integrated Products.
*P
17 T5IN
T5OUT 12
FORCEON 13
16 R1OUTB
FORCEOFF 14
15 INVALID
SSOP
________________________________________________________________ Maxim Integrated Products
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.
1
MAX3238
_______________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.
MAX3238
+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
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
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.
ELECTRICAL CHARACTERISTICS
(V CC = +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.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
1.0
10
UNITS
DC CHARACTERISTICS
Supply Current, AutoShutdown Plus
VCC = 3.3V or 5.0V, TA = +25°C, receivers idle,
transmitters idle, FORCEON = GND,
FORCEOFF = VCC
Supply Current, Shutdown
FORCEOFF = GND, TA = +25°C
1.0
10
Supply Current, AutoShutdown Plus
Disabled
FORCEON = FORCEOFF = VCC, no load
0.5
2.0
mA
0.8
V
µA
µA
LOGIC INPUTS AND RECEIVER OUTPUTS
Input Logic Threshold Low
Input Logic Threshold High
T_IN, FORCEON, FORCEOFF
VCC = 3.3V
2.0
VCC = 5.0V
2.4
V
Input Leakage Current
T_IN, FORCEON, FORCEOFF
±0.01
±1.0
µA
Output Leakage Current
Receivers disabled
±0.05
±10
µA
Output Voltage Low
IOUT = 1.6mA
0.4
V
Output Voltage High
IOUT = -1.0mA
VCC 0.6
VCC 0.1
V
RECEIVER INPUTS
Input Voltage Range
Input Threshold Low
Input Threshold High
-25
0.6
1.2
VCC = 5.0V
0.8
1.5
1.5
2.4
VCC = 5.0V
1.8
2.4
2
0.3
TA = +25°C
3
5
_______________________________________________________________________________________
V
V
VCC = 3.3V
Input Hysteresis
Input Resistance
25
VCC = 3.3V
V
V
7
kΩ
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus
(V CC = +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.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
AutoShutdown (FORCEON = GND, FORCEOFF = VCC)
Positive threshold
2.7
Receiver Input Threshold to
INVALID Output High
Figure 7a
Receiver Input Threshold to
INVALID Output Low
Figure 4a
INVALID Output Voltage Low
IOUT = 1.6mA
INVALID Output Voltage High
IOUT = -1.0mA
Receiver Positive or Negative
Threshold to INVALID High (tINVH)
VCC = 5V, Figure 4b
0.1
µs
Receiver Positive or Negative
Threshold to INVALID Low (tINVL)
VCC = 5V, Figure 4b
50
µs
Receiver or Transmitter Edge to
Transmitters Enabled (tWU)
VCC = 5V, Figure 4b (Note 2)
25
µs
Receiver or Transmitter Edge to
Shutdown (tAUTOSHDN)
Figure 4b (Note 2)
V
Negative threshold
-2.7
-0.3
0.3
V
0.4
V
VCC 0.6
V
15
30
60
sec
TRANSMITTER OUTPUTS
Output Voltage Swing
All transmitter outputs loaded with 3kΩ to ground
±5.0
±5.4
Output Resistance
VCC = V+ = V- = GND, TOUT = 2V
300
10M
Output Short-Circuit Current
Output Leakage Current
V
Ω
VCC ≤ 3.6V
±35
±60
VCC > 3.6V
±40
±100
VOUT = ±12V, VCC = 0V to 5.5V,
transmitters disabled
±25
mA
µA
TIMING CHARACTERISTICS
Maximum Data Rate
RL = 3kΩ, CL = 1000pF, one transmitter switching
250
kbps
tPHL
0.15
tPLH
0.15
Receiver Propagation Delay
R_IN to R_OUT,
CL = 150pF
Receiver Output Enable Time
Normal operation
200
ns
Receiver Output Disable Time
Normal operation
200
ns
Transmitter Skew
| tPHL - tPLH |
100
ns
Receiver Skew
| tPHL - tPLH |
50
ns
Transition-Region Slew Rate
VCC = 3.3V,
TA = +25°C,
RL = 3Ω to 7kΩ,
measured from +3V to
-3V or -3V to +3V
CL = 150pF to 1000pF
6
µs
30
V/µs
CL = 150pF to 2500pF
4
30
Note 2: A transmitter/receiver edge is defined as a transition through the transmitter/receiver input logic thresholds.
_______________________________________________________________________________________
3
MAX3238
ELECTRICAL CHARACTERISTICS (continued)
__________________________________________Typical Operating Characteristics
(VCC = +3.3V, 250kbps data rate, 0.1µF capacitors, all transmitters loaded with 3kΩ, TA = +25°C, unless otherwise noted.)
FOR DATA RATES UP TO 250kbps
1 TRANSMITTER 250kbps
4 TRANSMITTERS 15.6kbps
LOADED 3kΩ + CL
-2.5
+SLEW
10
8
1 TRANSMITTER 250kbps
4 TRANSMITTERS 15.6kbps
LOADED 3kΩ + CL
6
60
SUPPLY CURRENT (mA)
2.5
–SLEW
12
70
MAX3238-02
5.0
0
14
MAX3238 TOC-01
VOUT+
SLEW RATE (V/µs)
7.5
SUPPLY CURRENT vs. LOAD CAPACITANCE
WHEN TRANSMITTING DATA
SLEW RATE
vs. LOAD CAPACITANCE
4
250kbps
50
120kbps
40
30
20
VOUT–
-5.0
-7.5
0
0
0
1000
2000
3000
4000
5000
LOAD CAPACITANCE (pF)
20kbps
10
2
MAX3238 TOC-03
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
TRANSMITTER OUTPUT VOLTAGE (V)
MAX3238
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus
0
2000
4000
1000
3000
LOAD CAPACITANCE (pF)
5000
0
2000
4000
1000
3000
LOAD CAPACITANCE (pF)
5000
______________________________________________________________Pin Description
4
PIN
NAME
FUNCTION
1
C2+
Positive Terminal of Inverting Charge-Pump Capacitor
2
GND
Ground
3
C2-
4
V-
5, 6, 7, 10, 12
T_OUT
8, 9, 11
R_IN
13
FORCEON
Force-Off Input. Drive high to override AutoShutdown Plus, keeping transmitters and
receivers on (FORCEOFF must be high) (Table 1).
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).
15
INVALID
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
18, 20, 21
R_OUT
25
C1-
Negative Terminal of Voltage-Doubler Charge-Pump Capacitor
26
VCC
+3.0V to +5.5V Supply Voltage
27
V+
+5.5V Generated by the Charge Pump
28
C1+
Negative Terminal of Inverting Charge-Pump Capacitor
-5.5V Generated by the Charge Pump
RS-232 Transmitter Outputs (T1OUT–T5OUT)
RS-232 Receiver Inputs (R1IN–R3IN)
TTL/CMOS Transmitter Inputs (T5IN–T1IN)
TTL/CMOS Receiver Outputs (R3OUT–R1OUT)
Positive Terminal of Voltage-Doubler Charge-Pump Capacitor
_______________________________________________________________________________________
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus
MAX3238
Table 1. Output Control Truth Table
FORCEON
FORCEOFF
AUTOSHUTDOWN
PLUS*
X
0
X
1
1
X
0
1
0
1
OPERATION
STATUS
T_OUT
R_OUT
R1OUTB
Shutdown
(Forced Off)
High-Z
High-Z
Active
Normal Operation
(Forced On)
Active
Active
Active
<30sec*
Normal
Operation
(AutoShutdown
Plus)
Active
Active
Active
>30sec*
Shutdown
(AutoShutdown
Plus)
High-Z
Active
Active
X = Don’t Care
*Time since last receiver or transmitter input transition.
_______________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.
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.
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
VCC is set to 0V in shutdown to accommodate peripherals, such as UARTs (Figure 2).
LapLink is a trademark of Traveling Software.
_______________________________________________________________________________________
5
MAX3238
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus
POWER
MANAGEMENT
UNIT OR
KEYBOARD
CONTROLLER
VCC
FORCEOFF
FORCEON
INVALID
PROTECTION
DIODE
MAX3238
PREVIOUS
RS-232
VCC
I
Rx
T1
5kΩ
UART
T2
Tx
T3
CPU
I/O
CHIP
WITH
UART
GND
SHDN = GND
T4
RS-232
T5
(a)
OLDER RS-232: POWERED-DOWN UART DRAWS CURRENT FROM ACTIVE
RECEIVER OUTPUT IN SHUTDOWN.
R1
VCC
R2
TO
µP
R3
LOGIC
TRANSITION
DETECTOR
I
PROTECTION
DIODE
Figure 1. Interface Under Control of PMU
6
R1OUTB
VCC
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 disconnected 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
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
Rx
THREE-STATED
UART
5kΩ
Tx
GND
(b)
R1IN
R1OUT
T1IN
FORCEOFF = GND
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.
Figure 2. The MAX3238 detects RS-232 activity when the
UART and interface are shut down.
_______________________________________________________________________________________
T1OUT
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus
MAX3238
Table 2. INVALID Truth Table
+0.3V
RS-232 SIGNAL PRESENT AT
ANY RECEIVER INPUT
INVALID OUTPUT
Yes
H
No
L
R_IN
30µs
TIMER
R
-0.3V
INVALID
INVALID ASSERTED IF ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR
AT LEAST 30µs.
Figure 3a. INVALID Functional Diagram, INVALID Low
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 transmitter outputs are disabled (high impedance). The time
required to exit shutdown is typically 25µs (Figure 4b).
+2.7V
R_IN
30µs
TIMER
R
-2.7V
INVALID
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
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.
T_IN
__________Applications Information
R_IN
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 CBYPASS, to maintain the proper ratios (C1 to the
other capacitors).
EDGE
DETECT
FORCEOFF
S
30sec
TIMER
EDGE
DETECT
AUTOSHDN
R
FORCEON
Figure 3c. AutoShutdown Plus Logic
FORCEOFF
POWERDOWN*
FORCEON
AUTOSHDN
* POWERDOWN IS ONLY AN INTERNAL SIGNAL.
IT CONTROLS THE OPERATIONAL STATUS OF
THE TRANSMITTERS AND THE POWER SUPPLIES.
Figure 3d. Power-Down Logic
_______________________________________________________________________________________
7
MAX3238
+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 capacitors 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-.
INVALID HIGH
RECEIVER INPUT LEVELS
+2.7V
INDETERMINATE
+0.3V
0V
Table 3. Required Minimum Capacitance
Values
INVALID LOW
-0.3V
INDETERMINATE
VCC
(V)
C1
(µF)
C2, C3, C4, CBYPASS
(µF)
3.0 to 3.6
0.22
0.22
3.15 to 3.6
0.1
0.1
4.5 to 5.5
0.047
0.33
3.0 to 5.5
0.22
1
-2.7V
INVALID HIGH
Figure 4a. Receiver Positive/Negative Thresholds for INVALID
INVALID
REGION
*
RECEIVER
INPUTS
VOLTAGE
**
TRANSMITTER
INPUTS
VOLTAGE
TRANSMITTER
OUTPUTS
VOLTAGE
INVALID
OUTPUT
VCC
0
INVL
tAUTOSHDN
tAUTOSHDN
tWU
tWU
V+
VCC
0
V* ALL RECEIVERS/TRANSMITTERS INACTIVE
** ANY ONE RECEIVER/TRANSMITTER BECOMES ACTIVE
FORCEON = GND, FORCEOFF = VCC
Figure 4b. AutoShutdown Plus and INVALID Timing Diagram
8
_______________________________________________________________________________________
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus
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.
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
POWERSUPPLY
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.
5
3.3
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.
Compatible with ACT and HCT
CMOS, and with AC, HC, or
CD4000 CMOS.
VCC
VCC
C1+
V+
C3*
C1
C1-
FORCEON =
FORCEOFF
2V/div
T2OUT
C2+
MAX3238
VC4
C2
C2-
T_ OUT
T_ IN
2V/div
R_ IN
R_ OUT
T1OUT
VCC = 3.3V
C1 - C4 = 0.1µF
5µs/div
Figure 5. Transmitter Outputs when Exiting Shutdown or
Powering Up
5kΩ
FORCEON
VCC
FORCEOFF
1000pF
GND
*C3 CAN BE RETURNED TO VCC OR GND.
Figure 6. Loopback Test Circuit
_______________________________________________________________________________________
9
MAX3238
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.
MAX3238
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus
5V
0V
T1IN
5V
0V
T1IN
+5V
+5V
0V
T1OUT
T1OUT
0V
-5V
-5V
5V
0V
5V
R1OUT
0V
VCC = 3.3V
C1 - C4 = 0.1µF
CLOAD = 1000pF
2µs/div
Figure 7. Loopback Test Result at 120kbps
R1OUT
VCC = 3.3V
C1 - C4 = 0.1µF
CLOAD = 1000pF
2µs/div
Figure 8. Loopback Test Result at 250kbps
___________________Chip Information
TRANSISTOR COUNT: 1404
10
______________________________________________________________________________________
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus
MAX3238
__________Typical Operating Circuit
0.1µF
26
VCC
28 C1+
0.1µF
V+ 27
*
0.1µF
25 C1-
MAX3238
1 C2+
0.1µF
V- 4
0.1µF
3 C224 T1IN
T1
23 T2IN
LOGIC
INPUTS
T2
22 T3IN
T3
19 T4IN
T4
17 T5IN
T5
T1OUT 5
T2OUT 6
T3OUT 7
RS-232
OUTPUTS
T4OUT 10
T5OUT 12
14 FORCEOFF
AUTOSHUTDOWN PLUS
INVALID 15
13 FORCEON
16 R1OUTB
21 R1OUT
R1IN 8
R1
5kΩ
LOGIC
OUTPUTS
20 R2OUT
R2IN 9
R2
RS-232
INPUTS
5kΩ
18 R3OUT
R3IN 11
R3
5kΩ
GND
2
*C3 MAY BE RETURNED TO EITHER VCC OR GND.
______________________________________________________________________________________
11
MAX3238
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus
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.)
DIM
α
E
H
C
L
A
A1
B
C
D
E
e
H
L
α
INCHES
MILLIMETERS
MIN
MAX
MIN
MAX
0.068
0.078
1.73
1.99
0.002
0.008
0.05
0.21
0.010
0.015
0.25
0.38
0.004
0.008
0.09
0.20
SEE VARIATIONS
0.205
0.209
5.20
5.38
0.0256 BSC
0.65 BSC
0.301
0.311
7.65
7.90
0.025
0.037
0.63
0.95
0˚
8˚
0˚
8˚
DIM PINS
e
SSOP
SHRINK
SMALL-OUTLINE
PACKAGE
A
B
A1
D
D
D
D
D
14
16
20
24
28
INCHES
MILLIMETERS
MAX
MIN MAX MIN
6.33
0.239 0.249 6.07
6.33
0.239 0.249 6.07
7.33
0.278 0.289 7.07
8.33
0.317 0.328 8.07
0.397 0.407 10.07 10.33
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
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.
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