WM8352 datasheet(188/336 Pages) WOLFSON

188 / 336 page

WM8352

Production Data

PD, February 2011, Rev 4.4

188

21 VOLTAGE REFERENCES

The WM8352 generates several reference voltages used for different purposes.

The main reference voltage VREF, and additional internal references derived from it, are used in the

DC-DC converters, the LDO regulators and the auxiliary ADC. VREF is highly stable, accurate, and

independent of the supply voltage. It can be trimmed for improved accuracy.

The VRTC regulator (see Section 17.6) uses a separate, low-power reference at start-up.

The mid-rail reference VMID is used in the audio CODEC. It is generated from AVDD.

Each reference voltage is internally provided to those parts of the WM8352 where it is needed.

21.1 MAIN REFERENCE (VREF)

The main reference generates a highly accurate reference voltage VREF. It requires a decoupling

capacitor on the C_REF pin; a 2.2uF X5R capacitor is recommended, as noted in Section 29.2; and

an accurate resistor on the R_REF pin; a 100k

Ω (1%) resistor is recommended, as noted in

Section 29.2.

The WM8352 will malfunction if those components are omitted.

The accuracy of supply voltages generated by the WM8352 depends on VREF, and can be improved

by trimming. This scales VREF by up to +15/-16% in 1% steps, to compensate for deviations from

the nominal value.

The main reference can be overdriven with an externally generated reference voltage, if desired.

21.2 LOW-POWER REFERENCE

The low-power reference determines the accuracy of VRTC on start-up. Once the main bandgap has

been trimmed and has settled VRTC switches across to the main bandgap for greater accuracy.

WM8352 bảng dữ liệu(PDF) 188 Page - Wolfson Microelectronics plc