User's Manual

LZT 123 1834 49
5.8 Powering the Module ON and OFF (ON/OFF)
Pin Name Direction Function
14 ON/OFF Input Device on/off control
5.8.1 Turning the Module On
Figure 5.8-1 Power On timing
The GR64 power ON sequence is shown above. The significant signals are VCC,
ON/OFF and VREF, shown by solid lines. The other signals (in dashed lines) are
internal to the module and are shown for reference purposes only.
Initially, power is supplied to the VCC pins. The presence of power raises the ON/OFF
through a pull-up resistor to VCC potential. In order to power the module, ON/OFF is
pulled to ground. Once ON/OFF has been held low for 125ms (denoted by t
1
) the
primary LDOs power up; the VREF signal comes from one of the primary LDOs. For
module variants where VREF supplies a reference voltage to the host, it acts as a
useful indicator that the baseband is powered.