WM8742GEDSSLASHRV datasheet(17/66 Pages) CIRRUS

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WM8742

Rev 4.4

DVDD

Vpor_lo

Vpord

DGND

Internal POR active

INTERNAL

DIGITAL PORB

Device Ready

Internal

POR active

No Power

POR

Undefined

Vpor_hi

Figure 8 DVDD Power up Sequence

Test Conditions

DVDD = 3.3V, DGND = 0V, TA = +25

oC, TA_max = +125oC, TA_min = -25oC, DVDDmax = 3.6V, DVDDmin = 3.0V

PARAMETER

SYMBOL

TEST CONDITIONS

MIN

TYP

MAX

UNIT

Power Supply Input Timing Information

DVDD level to POR rising

edge (DVDD rising)

Vpor_hi

Measured from DGND

1.86

DVDD level to POR falling

edge (DVDD falling)

Vpor_lo

Measured from DGND

1.83

Table 7 Digital POR Timing

In a real application the designer is unlikely to have control of the relative power up sequence of

AVDD and DVDD.

The POR circuit ensures a reasonable delay between applying power to the

device and Device Ready.

Figure 7 and Figure 8 show typical power up scenarios in a real system. DVDD must be established

before the device can be written to. Any writes to the device before device ready will be ignored.

Note: DVDD must be established before the MCLK is started. This will ensure all synchronisation

circuitry within the device is fully initialised and ready.

AVDD must be established before the device will output any signal. Whilst the device will output

signal as soon as the Internal Analogue PORB indicates device ready, normal operation is not

possible until the VMID pin has reached the midrail voltage.

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