WM8978CGEFLSLASHV datasheet(19/118 Pages) WOLFSON

номер детали	WM8978CGEFL/V

подробное описание детали	Stereo CODEC with Speaker Driver

PDF	118 Pages

Scroll/Zoom	100%

производитель	WOLFSON [Wolfson Microelectronics plc]

домашняя страница	http://www.wolfsonmicro.com

Logo

19 / 118 page

Production Data

WM8978

PD, Rev 4.5, October 2011

INTERNAL POWER ON RESET CIRCUIT

Figure 6 Internal Power on Reset Circuit Schematic

The WM8978 includes an internal Power-On-Reset Circuit (POR), as shown in Figure 6, which is

used 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 7 Typical Power up Sequence where AVDD is Powered before DVDD

Figure 7 shows a typical power-up sequence where AVDD comes up first. When AVDD goes above

the minimum threshold, Vpora, there is enough voltage for the circuit to guarantee PORB is asserted

low and the chip is held in reset. In this condition, all writes to the control interface are ignored. AVDD

will then ramp up to full supply level. Next DVDD rises to Vpord_on and PORB is released high 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 Vpora_off.

WM8978CGEFL/V датащи(PDF) 19 Page - Wolfson Microelectronics plc