XR19L200_07 Datasheet, PDF (13/40 Pages) Exar Corporation – SINGLE CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER

XR19L200
REV. 1.0.1
SINGLE CHANNEL INTEGRATED UART AND RS-232 TRANSCEIVER
2.14.1.2 UART active, charge pump of RS-232 transceiver shut down
If the ACP pin is HIGH and the UART portion of the L200 is not in sleep mode, then the charge pump will
automatically shut down to conserve power if the following conditions are true:
■ no activity on the TXD output signals
■ RXD input signal has been idling LOW for approximately 30 seconds
When these conditions are satisfied, the L200 shuts down the charge pump and tri-states the RS-232 drivers
to conserve power. In this mode, the RS-232 receivers are fully active and the internal registers of the L200
can be accessed. The time for the charge pump to resume normal operation after exiting the sleep mode is
typically 45µs. It will wake up by any of the following:
■ a receive data start bit transition on the RXD input (LOW to HIGH)
■ a data byte is loaded to the transmitter, THR or FIFO
Because the receivers are fully active when the charge pump is turned off, any data received will be transferred
to/from the UART without any issues.
2.14.2 Full Sleep Mode
In full sleep mode, the L210 shuts down the charge pump and the internal oscillator. The L210 enters the full
sleep mode if the following conditions are satisfied:
■ the UART portion of the L210 is already in sleep mode (no output on XTAL2)
■ the ACP (Autosleep for Charge Pump) pin is HIGH
When these conditions are satisfied, both the UART and the charge pump will be in the sleep mode. In this
mode, the RS-232 receivers are fully active and the internal registers of the L200 can be accessed. The L200
exits the full sleep mode if either the ACP pin becomes LOW or the internal oscillator starts up. The time for the
charge pump to resume normal operation after exiting the full sleep mode is typically 45µs.
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