MAX3238CAI ,+3.0V to +5.5V / 1A / up to 250kbps / True RS-232 Transceiver with AutoShutdown PlusMAX3238*19-1144; Rev 0; 9/96+3.0V to +5.5V, 1µA, up to 250kbps, TrueRS-232 Transceiver with AutoShu ..
MAX3238CAI+ ,+3.0V to +5.5V, 1µA, Up to 250kbps, True RS-232 Transceiver with AutoShutdown PlusELECTRICAL CHARACTERISTICS(V = +3.0V to +5.5V; C1–C4 = 0.1µF (tested at 3.3V ±5%), C1–C4 = 0.22µF ( ..
MAX3238CAI+T ,+3.0V to +5.5V, 1µA, Up to 250kbps, True RS-232 Transceiver with AutoShutdown PlusFeaturesThe MAX3238 true RS-232 transceiver achieves a ♦ 1µA Supply Current Achieved with 1µA suppl ..
MAX3238CAI+T ,+3.0V to +5.5V, 1µA, Up to 250kbps, True RS-232 Transceiver with AutoShutdown Plusapplications. A proprietary, high-efficiency,______________Ordering Informationdual charge-pump pow ..
MAX3238CAI-T , 3.0V to 5.5V, 1μA, up to 250kbps, True RS-232 Transceiver with AutoShutdown Plus
MAX3238CDB ,3-V to 5.5-V Multichannel RS-232 Line Driver/Receiver/sc/package.Please be aware that an important notice concerning availability, standard warranty, an ..
MAX6751KA29+ ,µP Reset Circuits with Capacitor-Adjustable Reset/Watchdog Timeout DelayMAX6746–MAX6753 μP Reset Circuits with Capacitor-Adjustable Reset/Watchdog Timeout Delay
MAX6751KA31+T ,µP Reset Circuits with Capacitor-Adjustable Reset/Watchdog Timeout Delayfeatures • Manual-Reset Input Optionimmunity to power-supply transients.• Push-Pull or Open-Drain R ..
MAX6751KA46+T ,µP Reset Circuits with Capacitor-Adjustable Reset/Watchdog Timeout DelayApplicationsVIN● Medical EquipmentMAX6749● AutomotiveMAX4751● Intelligent InstrumentsVCC● Portable ..
MAX6753KA30/V+T ,µP Reset Circuits with Capacitor-Adjustable Reset/Watchdog Timeout DelayApplicationsVIN● Medical EquipmentMAX6749● AutomotiveMAX4751● Intelligent InstrumentsVCC● Portable ..
MAX6756UKTD3+T ,Low-Power, Single/Dual-Voltage Window DetectorsFeaturesThe MAX6754–MAX6764 low-power window detec- ● Single/Dual-Supply Voltage Monitorstors monit ..
MAX6756UKWD3+T ,Low-Power, Single/Dual-Voltage Window DetectorsMAX6754–MAX6764 Low-Power, Single/Dual-Voltage WindowDetectors
MAX3238CAI-MAX3238EAI
+3.0V to +5.5V / 1A / up to 250kbps / True RS-232 Transceiver with AutoShutdown Plus
_______________General DescriptionThe 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 VCCcompletely removed.
The MAX3238 is available in a space-saving SSOP
package.
________________________ApplicationsNotebook, Subnotebook, and Palmtop
Computers
High-Speed Modems
Battery-Powered Equipment
Hand-Held Equipment
Peripherals
Printers
AutoShutdown Plus is a trademark of Maxim Integrated Products.
*Patents Pending
____________________________Features1µA Supply Current Achieved with
AutoShutdown PlusGuaranteed Data Rate: 250kbps 1µA Low-Power ShutdownReceivers Active in AutoShutdown Plus ModeFlow-Through Pinout Meets EIA/TIA-232 Specifications Down to 3.0VGuaranteed 6V/µs Slew Rate
MAX3238
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus™
__________________Pin Configuration19-1144; Rev 0; 9/96
MAX3238
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus™
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= TMINto 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, 10sec) ............................+300°C
Note 1:V+ and V- can have a maximum magnitude of +7V, but their absolute difference can not exceed +13V.
MAX3238
+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%); TA= TMINto TMAX; unless otherwise noted. Typical values are at TA= +25°C.)
Note 2:A transmitter/receiver edge is defined as a transition through the transmitter/receiver input logic thresholds.
______________________________________________________________Pin DescriptionTRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
MAX3238 TOC-01
LOAD CAPACITANCE (pF)
TRANSMITTER OUTPUT VOLTAGE (V)
SLEW RATE
vs. LOAD CAPACITANCE
MAX3238-02
SLEW RATE (V/
LOAD CAPACITANCE (pF)
SUPPLY CURRENT vs. LOAD CAPACITANCE
WHEN TRANSMITTING DATA
MAX3238 TOC-03
SUPPLY CURRENT (mA)
LOAD CAPACITANCE (pF)
__________________________________________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™
MAX3238
+3.0V to +5.5V, 1µA, up to 250kbps, True
RS-232 Transceiver with AutoShutdown Plus™
_______________Detailed Description
Dual Charge-Pump Voltage ConverterThe 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 TransmittersThe 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 FORCEOFFis 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 ReceiversThe 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
VCCis set to 0V in shutdown to accommodate peripher-
als, such as UARTs (Figure 2).
Table 1. Output Control Truth TableX = 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™
AutoShutdown Plus Mode1µA supply current is achieved with Maxim’s
AutoShutdown Plus feature, which operates when
FORCEOFFis 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-
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
INVALIDoutput is high when the receivers are active.
Since INVALIDindicates the receiver inputs’ condition,
it can be used in any mode (Figure 3).
