WM8352 datasheet(173/336 Pages) WOLFSON

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Production Data

WM8352

PD, February 2011, Rev 4.4

173

19.3 VOLTAGE SCALING AND REFERENCES

For inputs AUX1, AUX2, AUX3 and AUX4, the AUXADC measurements may be referenced to either

VRTC or VREF (see Section 21). The selected reference can be selected independently for each

input, using the control fields described in Table 116. In the case of USB, BATT, LINE and

Temperature, the AUXADC measurements are referenced to VRTC.

In the case of AUXADC measurements which are referenced to VREF, a buffered copy of VREF is

used as an input to the AUXADC. Setting the AUXADC_RBMODE field allows this buffer to be

enabled at all times when the AUXADC is enabled, or else to only be enabled when a VREF-

referenced measurement is made.

In order to measure voltages that may be higher than VRTC or VREF, a programmable divider is

provided on each of AUX1, AUX2, AUX3 and AUX4. These are controlled using the

AUXADC_SCALEn bits, allowing the inputs to be divided by 1, 2 or 4. In the case of USB, BATT and

LINE, a fixed ‘divide by 2’ applies.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R152 (98h)

AUX1

R153 (99h)

AUX2

R154 (9Ah)

AUX3

R155 (9Bh)

AUX4

14:13

AUXADC_SCAL

En [1:0]

AUXn input select

00 = Off

01 = Input divided by 1

10 = Input divided by 2

11 = Input divided by 4

AUXADC_REFn

AUXn reference select

0 = AUXn measured relative to

VRTC

1 = AUXn measured relative to

VREF

R145 (91h)

Digitizer Control

(2)

AUXADC_RBM

ODE

Enable for AUXADC bandgap

(VREF) buffer.

0 = AUXADC REFBUF is only

enabled during conversions that

use the VREF as a reference

1 = AUXADC REFBUF is always

enabled when the AUXADC is

enabled

Table 116 AUXADC Reference Selection

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