wm9081 Wolfson Microelectronics plc, wm9081 Datasheet - Page 31

• 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

Pre-Production
POWER ON RESET CIRCUIT
Figure 23 Typical CODEC Power up Sequence where AVDD is Powered before DCVDD
w
Figure 22 Internal Power on Reset Circuit Schematic
The WM9081 includes an internal CODEC Power-On-Reset Circuit, as shown in Figure 22, which is
used to reset the CODEC digital logic into a default state after power up. The CODEC POR circuit is
powered from AVDD and monitors DCVDD. It asserts PORB low if AVDD or DCVDD is below a
minimum threshold.
Figure 23 shows a typical power-up sequence where AVDD comes up first. When AVDD goes above
the minimum threshold, V
low and the chip is held in reset. In this condition, all writes to the control interface are ignored. After
AVDD has reached its full supply level, DCVDD rises to V
registers are in their default state and writes to the control interface may take place.
On power down, where AVDD falls first, PORB is asserted low whenever AVDD drops below the
minimum threshold V
pora_off
pora
.
, there is enough voltage for the circuit to guarantee PORB is asserted
pord_on
and PORB is released high and all
PP, Rev 3.0, April 2009
WM9081
31