WM8352
Production Data
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 100kΩ (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.
PD, February 2011, Rev 4.4
188
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
