lm49370rl National Semiconductor Corporation, lm49370rl Datasheet - Page 56

• Manufacturer Part Number: lm49370rl
• Description: Audio Sub-system With An Ultra Low Emi, Spread Spectrum, Class D Loudspeaker Amplifier, A Dual-mode Stereo Headphone Amplifier, And A Dedicated Pcm Interface For Bluetooth Transceivers
• Manufacturer: National Semiconductor Corporation

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Bits
2:0
5:3
12.38 GPIO CONFIGURATION REGISTER
This register is used to control the GPIOs and to control the digital signal routing when using the ADC and DAC to perform sample
rate conversion.
12.39 DAC PATH COMPENSATION FIR CONFIGURATION REGISTERS
To allow for compensation of roll off in the DAC and analog filter sections an FIR compensation filter is applied to the DAC input
data at the original sample rate. Since the DAC can operate at different over sampling ratios the FIR compensation filter is pro-
grammable. By default the filter applies approx 2dB of compensation at 20kHz. 5 taps is sufficient to allow passband equalization
and ripple cancellation to around +/0.01dB.
The filter can also be used for precise digital gain and simple tone controls although a DSP or CPU should be used for more
powerful tone control if required. As the FIR filter must always be phase linear, the coefficients are symmetrical. Coefficients C0,
C1, and C2 are programmable, C3 is equal to C1 and C4 is equal to C0. The maximum power of this filter must not exceed that
of the examples given below:
6
7
ADC_SRC_MODE If set, the ADC analog is disabled and the digital is enabled, using the resampler input.
DAC_SRC_MODE This does not have to be set to use DAC in SRC mode, but should be set if the user wishes to disable the
GPIO_1_SEL
GPIO_2_SEL
Field
This configures the GPIO_1 pin.
This configures the GPIO_2 pin.
DAC analog to save power.
GPIO_1_SEL
GPIO_2_SEL
000
001
010
011
100
101
110
111
000
001
010
011
100
101
110
111
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
TABLE 38. GPIO Control (0x1Fh)
56
Dig_Mic R Clock
Dig_Mic L Clock
Class D Enable
Class D Enable
Dig_Mic_Data
Does What?
Does What?
Description
AUX Enable
SPI_SDO
SPI_SDO
Output 0
Output 1
Output 0
Output 1
Disable
Disable
Read
Read
Direction
Direction
Output
Output
Output
Output
Output
Output
Output
Output
Output
Output
Output
Input
Input
Input
HiZ
HiZ