LTC1535 Linear Technology, LTC1535 Datasheet - Page 4

• Manufacturer Part Number: LTC1535
• Description: Isolated RS485 Transceiver
• Manufacturer: Linear Technology

PI FU CTIO S
LTC1535
Note 1: Absolute Maximum Ratings are those values beyond which the
life of a device may be impaired.
Note 2: RS422 50 specification based on RS485 27 test.
Note 3: I
V
Note 4: Input fault conditions on the RS485 receiver are detected with a
fixed receiver offset. The offset is such that an input short or open will
result in a high data output.
Note 5: The low voltage detect faults when V
and reenables when greater than 4.4V. The fault can be monitored
through the weak driver output on RE.
Note 6: Value derived from 1 second test.
POWER SIDE
V
tor.
ST1 (Pin 2): DC Converter Output 1 to DC Transformer.
ST2 (Pin 3): DC Converter Output 2 to DC Transformer.
GND (Pin 4): Ground.
DI (Pin 25): Transmit Data TTL Input to the Isolated Side
RS485 Driver. Do not float.
DE (Pin 26): Transmit Enable TTL Input to the Isolated
Side RS485 Driver. A high level enables the driver. Do not
float.
RE (Pin 27): Receive Data Output Enable TTL Input. A low
level enables the receiver. This pin also provides a fault
output signal. (See Applications Information.)
RO (Pin 28): Receive Data TTL Output.
4
ELECTRICAL CHARACTERISTICS
CC2
CC
U
= GND2 5.25V.
(Pin 1): 5V Supply. Bypass to GND with 10 F capaci-
IN
is tested at V
U
CC2
U
= 5V, guaranteed by design from
CC2
or V
CC
drops below 4.2V
Note 7: The input signals are internally sampled and encoded. The internal
sample rate determines the data output jitter since the internal sampling is
asynchronous with respect to the external data. Nominally, a 4MHz
internal sample rate gives 250ns of sampling uncertainty in the input
signals.
Note 8: The maximum baud rate is 350kBd with 10% sampling jitter.
Lower baud rates have lower jitter.
Note 9: Start-up time is the time for communication to recover after a fault
condition. Data time-out is the time a fault is indicated on RE after data
communication has stopped.
ISOLATED SIDE
GND2 (Pin 11): Isolated Side Power Ground.
Z (Pin 12): Differential Driver Inverting Output.
Y (Pin 13): Differential Driver Noninverting Output.
V
Bypass to GND with 10 F capacitor.
B (Pin 15): Differential Receiver Inverting Input.
A (Pin 16): Differential Receiver Noninverting Input.
RO2 (Pin 17): Isolated Side Receiver TTL Output.
SLO (Pin 18): Slow Slew Rate Control of RS485 Driver. A
low level forces the driver outputs into slow slew rate
mode.
CC2
(Pin 14): 5V to 7.5V Supply from DC Transformer.