ASAHI KASEI [AK2301]
<MS0416-E-02> 12 2013/05
CIRCUIT DESCRIPTION
BLOCK FUNCTION
AMPT Op-amp for input gain adjustment.
A differential or single-ended input amplifier is composed with an external resistor.
The feedback resistor should be larger than 10k. Each pin definition is shown below.
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. A differential or single-ended amplifier is
composed with an external resistor. Each pin definition is shown below.
VFR: Negative op-amp input.
GSR: Op-amp output.
VR and GSR can be used as the differential output. In this case, more than 600 AC
load should be composed with external and feedback resistors.
AAF Integrated anti-aliasing filter (AAF)
It prevents signal noise around the sampling rate from folding back into the voice
band. AAF is a 2
nd order RC active low-pass filter.
CODEC
A/D
Converts analog signal to 8bit PCM data according to the compounding schemes of
ITU recommendation G.711; A-law or u-law. Even bits are inverted in A-Law
conversion. The compounding schemes is set by the ALAWN pin as follows:
"H": u-Law
"L": A-Law
The band limiting filter is also integrated.
CODEC
D/A
Expands and playbacks the 8bit PCM data from the DR pin according to the
compounding schemes of ITU recommendation G.711; A-law or u-law. Even bits are
inverted in A-Law converting. The compounding schemes is set by the ALAWN pin as
follows:
"H": u-Law
"L": A-Law
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 typ. 1.5V. 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. Characteristics are not guaranteed when connecting an external load. The
output should be buffered if using this voltage externally.
PCM I/F PCM data transferring rate is dependent on BCLK. Two kinds of data format (Long
Frame/Short Frame) are available. Each data format is automatically detected by the
AK2301. PCM data is input to the DR pin and output from the DX pin.
