SP232ACTSLASHTR datasheet(8/12 Pages) SIPEX

8 / 12 page

Date: 10/17/ 05

SP232A Series Enhanced RS232 Transceivers

Table 1. Wake-up Function Truth Table.

SP310A transmitter and receiver outputs in a high

impedance condition (tri-stated). The shutdown

mode is controlled on the SP312A by a logic “0”

on the SHUTDOWN control line (pin 18); this also

puts the transmitter outputs in a tri–state mode.

The receiver outputs can be tri–stated separately

during normal operation or shutdown by a logic

“1” on the ENABLE line (pin 1).

Wake–Up Feature for the SP312A

The SP312A has a wake–up feature that keeps

all the receivers in an enabled state when the

device is in the shutdown mode. Table 1 defines

the truth table for the wake–up function.

With only the receivers activated, the SP312A

typically draws less than 5

µA supply current.

In the case of a modem interfaced to a computer

in power down mode, the Ring Indicator (RI)

signal from the modem would be used to "wake

up" the computer, allowing it to accept data

transmission.

After the ring indicator signal has propagated

through the SP312A receiver, it can be used to

trigger the power management circuitry of the

computer to power up the microprocessor, and

bring the SD pin of the SP312A to a logic high,

taking it out of the shutdown mode. The receiver

propagation delay is typically 1

µs. The enable

time for V+ and V– is typically 2ms. After V+ and

V– have settled to their final values, a signal can

be sent back to the modem on the data terminal

ready (DTR) pin signifying that the computer is

ready to accept and transmit data.

Pin Strapping for the SP233ACT/ACP

The SP233A packaged in the 20–pin SOIC pack-

age (SP233ACT) has a slightly different pinout

thanthe SP233AinPDIPpackaging(SP233ACP).

To operate properly, the following pairs of pins

must be externally wired together:

Power

Up/Down

Receiver

Outputs

Down

Enable

Tri–state

Enable

Tri–state

Pins Wired

Together

SOIC

PDIP

Two V- Pins

10 & 17

12 & 17

Two C2+ Pins

12 & 15

11 & 15

Two C2- Pins

11 & 16

10 & 16

No Connections for

Pins 8, 13, and 14

Connect Pins 6 and 9

to GND

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