wm8961 Wolfson Microelectronics plc, wm8961 Datasheet - Page 17

• Manufacturer Part Number: wm8961
• Description: Ultra-low Power Stereo Codec With 1w Stereo Class D Speaker Drivers And Ground Referenced Headphone Drivers
• Manufacturer: Wolfson Microelectronics plc

INTERNAL POWER ON RESET CIRCUIT
w
WM8961
Figure 6 Typical Power up Sequence when AVDD is Applied before DVDD
INTERNAL PORB
DGND
AGND
DVDD
AVDD
LO
HI
No Power
V
V
pora
pord_on
POR
Undefined
Figure 5 Internal Power-on Reset Circuit Schematic
The WM8961 includes an internal Power-On-Reset Circuit, as shown in Figure 5, which is used to
reset the digital logic into a default state after power up. The POR circuit is powered from AVDD and
monitors DVDD. It asserts PORB low if AVDD or DVDD is below a minimum threshold.
Figure 6 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. Now
AVDD is at full supply level. Next DVDD rises to V
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
Internal
POR active
pora_off
pora
.
, there is enough voltage for the circuit to guarantee PORB is asserted
Device Ready
pord_on
and PORB is released high and all registers
Internal POR active
PP, August 2009, Rev 3.1
Pre-Production
V
pora_off
17