WM8985_07 WOLFSON [Wolfson Microelectronics plc], WM8985_07 Datasheet - Page 22

• Manufacturer Part Number: WM8985_07
• Description: Multimedia CODEC With Class D Headphone and Line Out
• Manufacturer: WOLFSON [Wolfson Microelectronics plc]

WM8985
Figure 9 Typical Power up Sequence where DCVDD is Powered before AVDD1
w
Table 2 Typical POR Operation (Typical Simulated Values)
1.
2.
3.
Figure 9 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 AVDD1 goes above the minimum
threshold, V
chip is held in reset. In this condition, all writes to the control interface are ignored. When AVDD1
rises to V
control interface may take place.
On power down, where DCVDD falls first, PORB is asserted low whenever DCVDD drops below the
minimum threshold V
Notes:
SYMBOL
V
V
V
V
V
pora_on
pora_off
pord_on
pord_off
If AVDD1 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 AVDD1 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.
pora
pora_on
pora
, there is enough voltage for the circuit to guarantee PORB is asserted low and the
, PORB is released high and all registers are in their default state and writes to the
MIN
0.4
0.9
0.4
0.5
0.4
por
pord_off
period is maintained even if DCVDD and AVDD1 have zero rise time. This
TYP
0.6
1.2
0.6
0.7
0.6
.
pora_off
MAX
0.8
1.6
0.8
0.9
0.8
or V
UNIT
pord_off
V
V
V
V
V
) then the chip will not reset and will resume normal
PP, Rev 3.5, March 2007
pora_off
Pre-Production
or V
pord_off
22
.