WM8741(2009) Просмотр технического описания (PDF) - Wolfson Microelectronics plc

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WM8741
(Rev.:2009)

24-bit 192kHz DAC with Advanced Digital Filtering

Wolfson Microelectronics plc 

Production Data

WM8741

Figure 8 DVDD Power up Sequence

Test Conditions

DVDD = 3.3V, DGND = 0V, TA = +25oC, TA_max = +125oC, TA_min = -25oC, DVDDmax = 3.6V, DVDDmin = 3.0V

PARAMETER

SYMBOL

Power Supply Input Timing Information

DVDD level to POR rising

edge (DVDD rising)

Vpor_hi

DVDD level to POR falling

edge (DVDD falling)

Vpor_lo

Table 7 Digital POR Timing

TEST CONDITIONS

Measured from DGND

Measured from DGND

MIN

TYP

MAX

1.86

1.83

UNIT

V

V

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.

w

PD, Rev 4.2, October 2009

17

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