wm9081 Wolfson Microelectronics plc, wm9081 Datasheet - Page 32

• Manufacturer Part Number: wm9081
• Description: Mono Dac With 2.6w Class Ab/d Speaker Driver, Dynamic Range Controller And Retune Mobile Parametric Equalizer
• Manufacturer: Wolfson Microelectronics plc

WM9081
Figure 24 Typical Power up Sequence where DCVDD is Powered before AVDD
w
Figure 24 shows a typical power-up sequence where DCVDD comes up first. First it is assumed that
DCVDD is already up to specified operating voltage. When AVDD goes above the minimum
threshold, V
chip is held in reset. In this condition, all writes to the control interface are ignored. When AVDD rises
to V
interface may take place.
On power down, where DCVDD falls first, PORB is asserted low whenever DCVDD drops below the
minimum threshold V
Table 9 Typical POR Operation at typical supply voltages
Notes
1.
2.
3.
4.
Vpora_off
Vpord_off
SYMBOL
Vpora_on
Vpord_on
Vpora
pora_on
If AVDD and DCVDD suffer a brown-out (i.e. drop below the minimum recommended operating
level but do not go below V
operation when the voltage is back to the recommended level again.
The chip will enter reset at power down when AVDD or DCVDD falls below V
This may be important if the supply is turned on and off frequently by a power management
system.
The minimum t
specification is guaranteed by design rather than test.
V
pora
, PORB is released high and all registers are in their default state and writes to the control
is a simulated value
pora
, there is enough voltage for the circuit to guarantee PORB is asserted low and the
MIN
por
pord_off
period is maintained even if DCVDD and AVDD have zero rise time. This
TYP
1.46
1.44
0.91
0.90
0.6
.
pora_off
MAX
or V
UNIT
pord_off
V
V
V
V
V
) then the chip will not reset and will resume normal
PP, Rev 3.0, April 2009
pora_off
Pre-Production
or V
pord_off
32
.