ASAHI KASEI [AK2301A]
<MS0300-E-01> 12 2005/8
CIRCUIT DESCRIPTION
BLOCK FUNCTION
AMPT Op-amp for input gain adjustment. This op-amp is used as an inverting or
differential amplifier. Adjusting the gain with external resistors. The resistor should
be larger than 10kΩ for the feedback resistor.
VFTN: Negative op-amp input.
VFTP: Positive op-amp input.
GST: Op-amp output.
AMPR Op-amp for output gain adjustment. This op-amp is used as an inverting amplifier.
Adjusting the gain with external resistors. The combined resistor larger than 8kΩ is
recommended for the feedback and the output load
VFR: Negative op-amp input.
GSR: Op-amp output.
VR and GSR can be used as the differential output.
AAF Integrated anti-aliasing filter which prevents signals around the sampling rate from
folding back into the voice band. AAF is a 2nd order RC active low-pass filter.
CODEC
A/D
Converts the analog signal to 14bit PCM data. The band limiting filter is also
intergrated.
CODEC
D/A
Converting the 14bit PCM data from the DR to the analog
D/A coverter is fed into the SMF to suppress the high frequency element.
SMF Extracts the inband signal from D/A output. It also corrects the sinx/x effect of the
D/A output.
BGREF Provide the stable analog ground voltage using an on-chip band-gap reference
circuit which is temperature compensated. The output voltage is 1.5V for 3.3V
An external capacitor of 1.0uF or larger should be connected between VREF and
VSS to stabilize analog ground (VREF). Please do not connect external load to
this pin. TAGND pin is used as the analog ground level output for the AMPT. An
external capacitor of 1.0uF or larger should be connected between TAGND and
VSS to stabilize analog ground.
PCM I/F For the PCM data rate, 256kHz or 512kHz are available. The 14bit PCM data is
input/output by the 2’s compliment 16bit serial data format. Two kinds of data
format (Long Frame/Short Frame) are available. Each data format is automatically
detected by AK2301A.
PCM data is input to DR pin and output from DX pin.
AMP1, AMP2
Universal op-amp for the filter of the external voice path. The maximum load is 8kΩ
(including the feedback resistor and AC load). These op-amps are assumed as
using for the inverting LPF with 20kHz cut off frequency.
