Power On/Off Sequencing - Siemens SXG 75 Service Repair Documentation

AMUX_IN2 LCD_RST_N
Current control.
The vibramotor is driven by a current sink function on the PM6650
/VIB_DRV VIB_DRV
Power Management.
Power on/off and backup functions
(100uF capacitor,
VCOIN
C1312)
/PON_RST PON_RST_N
/KPDPWR PHONE_ON
PS_HOLD /
PS_HOLD
JTAG_PS_HOLD
Analogue Multiplexer.
Analogue voltages sensed on the PM6650 are fed to an ADC on the MSM6250 for measurement.
AMUX_OUT AMUX_OUT
PM6650 signal interfaces

8.5 Power On/Off sequencing

8.5.1 Power-On sequence
The PM6650 includes circuitry to manage the power-on and off operations. Dedicated circuits
continuously monitor events that might trigger a power-on sequence. If any of the events occurs,
these circuits power-on the PM6650 IC and take the MSM device out of reset.
The inputs to the power-on circuit are:
• PHONE_ON. This is the input from the END/power key on the keypad. A low voltage on this line
initiates the power-up sequence.
• Voltage detected on POWER line. This indicates that an external supply has been connected.
• Real Time Clock alarm triggered. While the PM6650 IC is off the Real Time Clock (RTC) and its
oscillator source are still active. This allows continued monitoring of RTC alarms programmed via
software. If an alarm occurs while the PM6650 IC is off an alarm interrupt is generated and the
power-on sequence is initiated.
• Sudden Momentary Power Loss (SMPL) condition was detected and an SMPL recovery is initiated.
If the power-on circuits detect that the SMPL function is enabled when the PS_HOLD signal
is cleared, the power-on sequence is initiated.
The normal power-on sequence begins when the keypad power button is pressed; this pulls the
PM6650 PHONE_ON input to the PM6650 low. At this point the PM6650 holds the reset output to
the MSM6250 (PON_RST_N) low, and turns on the following power supplies in the following
sequence:
• VREG_MSMC
• VREG_MSME
• VREG_MSMP
• VREG_MSMA
• VREG_TCXO
Technical Documentation
TD_Repair_L3_SXG75_R1.0.pdf
LCD Reset.
Current sink for Vibrator Motor
Back-up capacitor. 100uF for 40 sec backup
Reset output to MSM6250
Direct connection to Power / End key
Power latch from MSM / JTAG
Multiplexer output to MSM6250 ADC
Company Confidential
2006©BenQ
Release 1.0
01/2006
Page 40 of 73