LTC1535(1999) Ver la hoja de datos (PDF) - Linear Technology

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LTC1535
(Rev.:1999)

Isolated RS485 Transceiver

Linear Technology 

LTC1535

ELECTRICAL CHARACTERISTICS

Note 1: Absolute Maximum Ratings are those values beyond which the

life of a device may be impaired.

Note 2: RS422 50Ω specification based on RS485 27Ω test.

Note 3: IIN is tested at VCC2 = 5V, guaranteed by design from

VCC2 = GND2 ≤ 5.25V.

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 VCC2 or VCC drops below 4.2V

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.

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.

PI FU CTIO S

POWER SIDE

VCC (Pin 1): 5V Supply. Bypass to GND with 10µF capaci-

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.

ISOLATED SIDE

GND2 (Pin 11): Isolated Side Power Ground.

Z (Pin 12): Differential Driver Inverting Output.

Y (Pin 13): Differential Driver Noninverting Output.

VCC2 (Pin 14): 5V to 7.5V Supply from DC Transformer.

Bypass to GND with 10µF 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.

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