1
LT1537
Advanced Low Power
5V RS232 Transceiver with
Small Capacitors
D
U
ESCRIPTIO
S
FEATURE
The LT
1537 is a three-driver, five-receiver RS232 trans-
ceiver, pin compatible with the LT1137A, offering perfor-
mance improvements and two shutdown modes. The
LT1537’s charge pump is designed for extended compli-
ance and can deliver over 35mA of load current. Supply
current is typically 8mA, competitive with similar CMOS
devices. An advanced driver output stage operates up to
250kbaud while driving heavy capacitive loads.
The LT1537 is fully compliant with all RS232 specifica-
tions. Special bipolar construction techniques protect the
drivers and receivers beyond the fault conditions stipu-
lated for RS232. Driver outputs and receiver inputs can be
shorted to
±25V without damaging the device or the
power supply generator. In addition, the RS232 I/O pins
are resilient to multiple
±5kV ESD strikes.
The transceiver has two shutdown modes. One mode
disables the drivers and the charge pump, the other shuts
down all circuitry. While shut down, the drivers and
receivers assume high impedance output states.
, LTC and LT are registered trademarks of Linear Technology Corporation.
s
Low Cost
s
Uses Small Capacitors: 0.1
F, 0.2F
s
1
A Supply Current in Shutdown
s
120kBaud Operation for RL = 3k, CL = 2500pF
s
250kBaud Operation for RL = 3k, CL = 1000pF
s
CMOS Comparable Low Power: 40mW
s
Operates from a Single 5V Supply
s
Easy PC Layout: Flow-through Architecture
s
Rugged Bipolar Design
s
Outputs Assume a High Impedance State When Off
or Powered Down
s
Improved Protection: RS232 I/O Lines Can Be Forced
to
±25V Without Damage
s
Output Overvoltage Does Not Force Current Back
into Supplies
s
Absolutely No Latch-Up
s
Available in SO Package
U
S
A
O
PPLICATI
s
Notebook Computers
s
Palmtop Computers
U
A
O
PPLICATI
TYPICAL
R
LT1537 TA02
LT1537 TA01
5V VCC
0.1
F
2
× 0.1F
0.1
F
TO
LINE
LT1537
1
2
3
4
5
6
7
8
9
10
11
12
13
14
DRIVER OUT
RX IN
DRIVER OUT
RX IN
DRIVER OUT
RX IN
28
27
26
25
24
23
22
21
20
19
18
17
16
15
2
× 0.1F
DRIVER IN
RX OUT
DRIVER IN
RX OUT
DRIVER IN
RX OUT
+
TO LOGIC
V–
V+
ON/OFF = 5V
+
DRIVER
DISABLE
GND
INPUT
DRIVER
OUTPUT
RL = 3k
CL = 2500pF
RECEIVER
OUTPUT
CL = 50pF
Output Waveforms