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MANUAL
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7/198 17-LXE 108 566 Uen
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3.1.2 Status Signals Recommended Circuitry
The status group contains five signals, one output from the application, three inputs to the application, and one bi-
directional signal.
3.1.2.1 MODULE_PWR_EN_B
This signal, located on pin 12 in the system connector, enables the main supply voltage in the phone module so
that it powers on. This is an open drain input to the phone module. Its reference voltage is VCC_MAIN.
Figure 15: MODULE_PWR_EN_B Recommendation
3.1.2.2 VREF
This signal, located on pin 2 in the system connector, provides the application with its logic supply voltage (VDIG).
The main purpose for this signal is for the application to current-amplify this signal and use it to supply its interface
circuits (VREF_CA). Transistor T1 can be switched to an N-channel, PNP, or P-channel depending on preferred
solution and VCC voltage level.
The input + and – signals of the OP-amp must be switched if a PNP, or P-channel transistor is used.
Figure 16: VREF Recommendation
The VREF-signal can also be used to detect if the module powers on (VREF_DET) or as an application “on
request”-signal (ALARM_DET) if the VRTC is used to set up an Alarm wakeup. VREF is then set high for 250ms
through the ALARM-signal. The application detects the low-to-high transition and performs a normal power on
sequence. If this signal is used to detect phone module status it is recommended that it is connected so that it can
detect 0.8V-3.0V high low to high transition even if the application is in a power down state.
