WM8900LGEFK/RV Wolfson Microelectronics, WM8900LGEFK/RV Datasheet - Page 27

• Manufacturer Part Number: WM8900LGEFK/RV
• Description: Audio CODECs Ultra Low Power Hi-Fi CODEC
• Manufacturer: Wolfson Microelectronics

Specifications of WM8900LGEFK/RV

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Production Data
INTERNAL POWER ON RESET CIRCUIT
Figure 10 Typical Power up Sequence where AVDD is Powered before DCVDD
w
Figure 9 Internal Power on Reset Circuit Schematic
The WM8900 includes an internal Power-On-Reset Circuit, as shown in Figure 9, which is used to
reset the digital logic into a default state after power up. The POR circuit is powered from AVDD
and monitors DCVDD. It asserts PORB low if AVDD or DCVDD is below a minimum threshold.
Figure 10 shows a typical power-up sequence where AVDD comes up first. When AVDD goes
above the minimum threshold, V
asserted 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 DCVDD rises to V
and all 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
pord_on
PD, August 2008, Rev 4.0
and PORB is released high
WM8900
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