WM8959 Wolfson Microelectronics Ltd., WM8959 Datasheet - Page 33

• Manufacturer Part Number: WM8959
• Description: Mobile Multimedia DAC with Dual-mode Class AB/D Speaker Driver
• Manufacturer: Wolfson Microelectronics Ltd.

w
Pre-Production
Figure 14 Typical Power up Sequence where DCVDD is powered before AVDD
Figure 14 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 1 Typical POR Operation (typical values, not tested)
Notes:
1.
2.
3.
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.
, PORB is released high and all registers are in their default state and writes to the control
pora
SYMBOL
V
V
V
V
, there is enough voltage for the circuit to guarantee PORB is asserted low and the
V
pord_off
pora_on
pora_off
pord_on
pora
por
pord_off
period is maintained even if DCVDD and AVDD have zero rise time. This
.
MIN
pora_off
1.52
0.92
TYP
0.9
0.6
1.5
or V
pord_off
MAX
) then the chip will not reset and will resume normal
UNIT
V
V
V
V
V
PP, May 2008, Rev 3.1
pora_off
WM8959
or V
pord_off
33
.