SP3221ECA datasheet(13/18 Pages) SIPEX

13 / 18 page

Date: 7/21/04

SP3221E +3.0V to +5.5V RS-232 Transceiver

Auto-Online Circuitry

The SP3221E device has an Auto-Online cir-

cuitry on board that saves power in the system

the device is designed into without changes to

the existing BIOS or operating system.

The SP3221E device incorporates an

Auto-Online circuit that automatically

enables itself when the cable is connected to

another RS232 device. Conversely, the Auto-

Online circuit also disables most of the internal

circuitry when the cable is disconnected and

goes into a standby mode where the device

typically draws 1

µA. This function is controlled

by the ONLINE pin. When this pin is tied to a

logic LOW, the Auto-Online function is active.

When the cable is disconnected, the receiver

inputs will be pulled down by its internal 5k

Ω

resistors to ground. When ONLINE is HIGH,

the Auto-Online mode is disabled.

When the SP3221E driver or internal charge

pump are disabled, the supply current is reduced

to 1

µA.

The Auto-Online mode can be overridden by the

SHUTDOWN pin. If this pin is a logic LOW,

the Auto-Online function will not operate

regardless of the logic state of the ONLINE pin.

Table 3 summarizes the logic of the Auto-Online

operating modes. The truth table logic of the driver

and receiver outputs can be found in Table 2.

The STATUS pin outputs a logic LOW signal

if the device is shutdown. This pin goes to a

logic HIGH when the external cable is connected

to another RS232 device.

When the SP3221E device is shutdown, the

charge pump is turned off. V+ charge pump

output decays to V

CC, the V- output decays to

GND. The decay time will depend on the size of

capacitors used for the charge pump. Once in

shutdown, the time required to exit the shut

down state and have valid V+ and V- levels is

typically 200

µs.

Tying ONLINE and SHUTDOWN together

will bypass the Auto-Online circuitry so this

connection acts like a shutdown input pin.

SP3221ECA Fiches technique(PDF) 13 Page - Sipex Corporation

SP3221ECA Fiches technique(HTML) 13 Page - Sipex Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Fiches technique Télécharger

Lien URL