wm8952 Wolfson Microelectronics plc, wm8952 Datasheet - Page 52

• Manufacturer Part Number: wm8952
• Description: Mono Adc With Microphone Pre-amplifier
• Manufacturer: Wolfson Microelectronics plc

WM8952
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RECOMMENDED POWER UP/DOWN SEQENCE
In order to minimise output pop and click noise, it is recommended that the WM8941 device is
powered up and down using one of the following sequences:
Power Up:
1.
2.
3.
4.
5.
6.
7.
8.
9.
Power Down:
1.
2.
3.
4.
5.
6.
7.
1. This step enables the internal device bias buffer and the VMID buffer for unassigned inputs. This
2. Choose the value of VMIDSEL bits based on the startup time (VMIDSEL = 10 for the slowest
Notes:
In addition to the power on sequence, it is recommended that the zero cross functions are used
when changing the volume in the PGAs to avoid any audible pops and clicks.
will provide a startup reference for all inputs. This will cause the inputs to ramp towards VMID in
a way that is controlled and predictable.
startup, VMIDSEL = 11 for the fastest startup). Startup time is defined by the value of the
VMIDSEL bits (the reference impedance) and the external decoupling capacitor on VMID.
Turn on external power supplies. Wait for supply voltages to settle.
Reset internal registers to default state (software reset).
Enable non-VMID derived bias generator (VMID_OP_EN = 1) and level shifters
Select Clock source to MCLK (CLKSEL = 0) and audio mode (Master or Slave).
Enable Power on Bias Control (POB_CTRL = 1) and VMID soft start
Set VMIDSEL[1:0] bits for 50kΩ reference string impedance.
Wait for the VMID supply to settle. *Note 2.
Enable analogue amplifier bias control (BIASEN = 1) and VMID buffer (BUFIOEN
Disable Power on Bias Control (POB_CTRL = 0) and VMID soft start
Enable non-VMID derived bias generator (VMID_OP_EN = 1).
Enable on Bias Control (POB_CTRL = 1).
Disable analogue amplifier bias control (BIASEN = 0) and VMID (VMIDSEL[1:0]
Enable Fast VMID Discharge (TOGGLE = 1) to discharge VMID capacitor.
Wait for VMID capacitor to fully discharge.
Reset all registers to their default state (software reset).
Turn off external power supply voltages.
(LVLSHIFT_EN = 1).
(SOFT_START = 1).
= 1). *Notes 1 and 2.
(SOFT_START = 0).
bits set to OFF).
PP, Rev 3.0, December 2008
Pre Production
52