WM8944B Datasheet, PDF (62/165 Pages) Cirrus Logic – Mono Low-Power CODEC with Video Buffer

WM8944B
LDO_VSEL [4:0]
LDO OUTPUT
LDO_VSEL [4:0]
LDO OUTPUT
00h
Vref x 1.42
10h
Vref x 2.85
01h
Vref x 1.50
11h
Vref x 3.00
02h
Vref x 1.58
12h
Vref x 3.16
03h
Vref x 1.66
13h
Vref x 3.32
04h
Vref x 1.74
14h
Vref x 3.49
05h
Vref x 1.82
15h
Vref x 3.63
06h
Vref x 1.90
16h
Vref x 3.79
07h
Vref x 1.97
17h
Vref x 3.95
08h
Vref x 2.06
18h
Vref x 4.12
09h
Vref x 2.13
19h
Vref x 4.28
0Ah
Vref x 2.21
1Ah
Vref x 4.42
0Bh
Vref x 2.29
1Bh
Vref x 4.58
0Ch
Vref x 2.37
1Ch
Vref x 4.75
0Dh
Vref x 2.45
1Dh
Vref x 4.90
0Eh
Vref x 2.53
1Eh
Vref x 5.06
0Fh
Vref x 2.69
1Fh
Vref x 5.23
Note – Vref is the applicable voltage reference, selected by LDO_REF_SEL.
Table 38 LDO Output Voltage Control
BG_VSEL [4:0]
BG VOLTAGE (V)
00h
1.200
01h
1.227
02h
1.253
03h
1.280
04h
1.307
05h
1.334
06h
1.360
07h
1.387
Table 39 Bandgap Voltage Control
BG_VSEL [4:0]
08h
09h
0Ah
0Bh
0Ch
0Dh
0Eh
0Fh
BG VOLTAGE (V)
1.414
1.440
1.467
1.494
1.520
1.547
1.574
1.600
REFERENCE VOLTAGES AND MASTER BIAS
This section describes the analogue reference voltage and bias current controls. It also describes the
VMID soft-start circuit for pop suppressed start-up and shut-down.
The analogue circuits in the WM8944B require a mid-rail analogue reference voltage, VMID. This
reference is generated via a programmable resistor chain. Together with the external decoupling
capacitor (connected to the VMIDC pin), the programmable resistor chain results in a slow, normal or
fast charging characteristic on the VMID reference. This is enabled using VMID_ENA and VMID_SEL.
The different resistor options controlled by VMID_SEL can be used to optimize the reference for
normal operation, low power standby or for fast start-up as described in Table 40.
The VMID resistor chain can be powered from the LDO output (LDOVOUT) or from the LDO supply
(LDOVDD). This is selected using VMID_REF_SEL.
Note that when VMID is selected as the LDO reference voltage, VMID cannot be generated from the
LDOVOUT supply voltage (VMID_REF_SEL = 1) and must be generated from the LDOVDD supply
voltage (VMID_REF_SEL = 0).
The VMID ratio can be selected using VMID_CTRL. This selects the ratio of VMID to the supply
voltage that has been selected by VMID_REF_SEL. VMID should be half of the LDOVOUT supply
voltage for maximum voltage swing. In the case where VMID_REF_SEL has selected the LDOVOUT
supply voltage, then VMID_CTRL should select the ratio “1/2”. In the case where VMID_REF_SEL
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