WM8199 查看數據表（PDF） - Cirrus Logic

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WM8199

20MSPS 16-bit CCD Digitiser

Cirrus Logic 

WM8199

Production Data

Figure 10 Typical Power up Sequence where DVDD1 is Powered before AVDD

Figure 10 shows a typical power-up sequence where DVDD1 is powered up first. It is assumed that

DVDD1 is already up to specified operating voltage. 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. When AVDD rises

to Vpora_on, 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 DVDD1 falls first, PORB is asserted low whenever DVDD1 drops below the

minimum threshold Vpord_off.

SYMBOL

TYP

UNIT

Vpora

0.6

V

Vpora_on

1.2

V

Vpora_off

0.6

V

Vpord_on

0.7

V

Vpord_off

0.6

V

Table 1 Typical POR Operation (typical values, not tested)

Note: It is recommended that every time power is cycled to the WM8199 a software reset is written

to the software register to ensure that the contents of the control registers are at their default values

before carrying out any other register writes.

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PD, Rev 4.4, July 2008

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