ICL3221, ICL3222, ICL3223, ICL3232, ICL3241, ICL3243

4. Application Information

FN4805 Rev.23.00

Page 17 of 36

Apr.26.19

With any of the above control schemes, the time required to exit powerdown and resume transmission is only

100µs. A mouse or other application may need more time to wake up from shutdown. If automatic powerdown is

being used, the RS-232 device reenters powerdown if valid receiver levels are not re-established within 30µs of

the ICL32xx powering up. Figure 11 on page 18 shows a circuit that keeps the ICL32xx from initiating automatic

Figure 8. Power Drain Through Powered Down Peripheral

Figure 9. Disabled Receivers Prevent Power Drain

Figure 10. Connections for Manual Powerdown when No Valid Receiver Signals are Present

Old

VCC

Powered

GND

SHDN = GND

VCC

Rx

Tx

VCC

Current

VOUT = VCC

Flow

RS-232 Chip

Down

UART

ICL324X

Transition

RX

TX

R2OUTB

R2OUT

T1IN

FORCEOFF = GND

VCC

VCC

To

R2IN

T1OUT

VOUT = HI-Z

Powered

OR SHDN = GND, EN = VCC

Detector

Down

UART

Wake-Up

Logic

PWR

FORCEOFF

INVALID

CPU

I/O

FORCEON

ICL3221/23/43

MGT

Logic

UART