wm8903 Wolfson Microelectronics plc, wm8903 Datasheet - Page 26

• Manufacturer Part Number: wm8903
• Description: Ultra Low Power Codec For Portable Audio Applications
• Manufacturer: Wolfson Microelectronics plc

WM8903
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INPUT PGA ENABLE
The input PGAs (Programmable Gain Amplifiers) and Multiplexers are enabled using register bits
INL_ENA and INR_ENA, as shown in Table 1.
Table 1 Input PGA Enable
To enable the input PGAs, the reference voltage VMID and the bias current must also be enabled.
See “Reference Voltages and Master Bias” for details of the associated controls VMID_RES and
BIAS_ENA.
INPUT PGA CONFIGURATION
The analogue input channels can each be configured in three different modes, which are as follows:
The mode is selected by the L_MODE and R_MODE fields for the Left and Right channels
respectively. The input pins are selected using the L_IP_SEL_N and L_IP_SEL_P fields for the Left
channel and the R_IP_SEL_N and R_IP_SEL_P for the Right channel. In Single-Ended mode,
L_IP_SEL_N alone determines the Left Input pin, and the R_IP_SEL_N determines the Right Input
pin.
The three modes are illustrated in Figure 23, Figure 24 and Figure 25. It should be noted that the
available gain and input impedance varies between configurations (see also “Electrical
Characteristics”). The input impedance is constant with PGA gain setting.
The Input PGA modes are selected and configured using the register fields described in Table 2.
R12 (0Ch)
Power
Management
0
REGISTER
ADDRESS



Single-Ended Mode (Inverting)
Differential Line Mode (Inverting)
Differential Mic Mode (Non-Inverting)
BIT
1
0
INL_ENA
INR_ENA
LABEL
DEFAULT
0
0
Left Input PGA Enable
0 = disabled
1 = enabled
Right Input PGA Enable
0 = disabled
1 = enabled
PP, Rev 3.1, August 2009
DESCRIPTION
Pre-Production
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