MAX3238CAI+T Maxim Integrated Products, MAX3238CAI+T Datasheet - Page 5

• Manufacturer Part Number: MAX3238CAI+T
• Description: IC TXRX RS-232 TRUE 28-SSOP
• Manufacturer: Maxim Integrated Products
• Type: Transceiverr

Specifications of MAX3238CAI+T

• Number Of Drivers/receivers: 5/3
• Protocol: RS232
• Voltage - Supply: 3 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 28-SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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 (V
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.
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 3k
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.
Table 1. Output Control Truth Table
X = Don’t Care
*Time since last receiver or transmitter input transition.
_______________Detailed Description
FORCEON
X
1
0
0
Dual Charge-Pump Voltage Converter
RS-232 Transceiver with AutoShutdown Plus
F F O O R R C C E E O O F F F F
+3.0V to +5.5V, 1µA, up to 250kbps, True
_______________________________________________________________________________________
0
1
1
1
RS-232 Transmitters
in parallel with 1000pF,
AUTOSHUTDOWN
<30sec*
>30sec*
PLUS*
X
X
Shutdown
(Forced Off)
Normal Operation
(Forced On)
Normal
Operation
(AutoShutdown
Plus)
Shutdown
(AutoShutdown
Plus)
CC
OPERATION
STATUS
)
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 V
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
V
als, such as UARTs (Figure 2).
CC
is set to 0V in shutdown to accommodate peripher-
T_OUT
High-Z
High-Z
Active
Active
R_OUT
High-Z
Active
Active
Active
RS-232 Receivers
CC
.
R1OUTB
Active
Active
Active
Active
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