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AS3542 3v2
Data Sheet, Strictly Confidential - D e ta i l e d D e s c r i p t i o n - S Y S T E M F u n c t i o n s
10.1.3 Start-up Sequence
The AFE offers different power-up sequences. While VPRG1 and VPRG2 pins are defining the regulator voltages
VPRG3 is setting the sequence of powering on the regulators during the start-up. These pins detect 5 logical input
states which shall come from an external resistor divider network.
At first, LDO2 (AVDD27) and LDO1 (AVDD17) are powered up. This cannot be influenced with the selection of specific
sequences below. LDO2 is necessary for the internal supply of the AFE, LDO1 could be turned off later if no audio
functionality is needed.
After power-up sequence all voltage settings and power on/off conditions of the described regulators can be pro-
grammed via the serial interface
10.1.4 XRES delay with PWGD pin
With using an exteral capacitor on PWGD, the XRES signal can be delayed. This delay can be calculated with the
10uA pull-up current and a comparator threshold of ~1V. Using a 100nF capacitance will give a delay of 10ms.
Table 29. Start-Up Sequence
CVDD1
CVDD2
PVDD1
PVDD2
VPRG1 (core)
open
1.2V
VPRG2 (peri)
vdd
2.5V
3.3V
3.3V
150k PU
2.8V
1.8V
3.3V
open
1.8V
3.3V
3.3V
150k PD
vss
3.3V
3.3V
3.3V
VPRG3 (sequence)
vdd
1
st
2
nd
3
rd
off
150k PU
1
st
2
nd
3
rd
3
rd
open
3
rd
2
nd
1
st
1
st
150k PD
vss
3
rd
2
nd
1
st
off