wm8350 Wolfson Microelectronics plc, wm8350 Datasheet - Page 191

• Manufacturer Part Number: wm8350
• Description: Wolfson Audioplus? Stereo Codec With Power Management
• Manufacturer: Wolfson Microelectronics plc

Production Data
21 VOLTAGE REFERENCES
21.1 MAIN REFERENCE (VREF)
21.2 LOW-POWER REFERENCE
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The WM8350 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 WM8350 where it is needed.
The main reference generates a highly accurate reference voltage VREF. It requires a decoupling
capacitor on the C_REF pin and an accurate resistor on the R_REF pin.
The accuracy of supply voltages generated by the WM8350 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.
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, June 2009, Rev 4.1
WM8350
191