WM8741(2009) データシートの表示（PDF） - Wolfson Microelectronics plc

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WM8741
(Rev.:2009)

24-bit 192kHz DAC with Advanced Digital Filtering

Wolfson Microelectronics plc 

WM8741

Production Data

INTERNAL POWER ON RESET CIRCUIT

The WM8741 includes two internal Power On Reset (POR) circuits which are used to reset the digital

logic into a default state after power up and to allow the analogue circuits to power-up silently.

The digital POR circuit is powered from DVDD. This circuit monitors DVDD and asserts the internal

digital reset if DVDD are below the minimum DVDD threshold which will allow the digital logic to

function.

The analogue POR circuit is powered from AVDD. The circuit monitors AVDD, tri-stating the DAC

outputs and isolating the internal reference resistor strings from AVDDL and AVDDR until there is

sufficient AVDD voltage to allow the analogue DAC stages to function correctly.

Figure 7 AVDD Power up Sequence

Test Conditions

AVDD = 5V, AGND = 0V, TA = +25oC, TA_max = +125oC, TA_min = -25oC, AVDDmax = 5.5V, AVDDmin = 4.5V

PARAMETER

SYMBOL

Power Supply Input Timing Information

AVDD level to POR rising

edge (AVDD rising)

Vpor_hi

AVDD level to POR falling

edge (AVDD falling)

Vpor_lo

Table 6 Analogue POR Timing

TEST CONDITIONS

Measured from AGND

Measured from AGND

MIN

TYP

2.00

1.84

MAX

UNIT

V

V

w

PD, Rev 4.2, October 2009

16

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