AK7750 Datasheet, PDF (75/77 Pages) Asahi Kasei Microsystems – Audio DSP with Built-in Hands-Free Phone Features

[ASAHI KASEI]
[AK7750]
Signal
10k
Vop
BIAS ^{0.1µ 4.7k}
10µ ⁺
4.7k
10k
Vop
-
+
10k
BIAS
10k
-
+
330
NJM2100
Vop = VA+ = 3.3V
330
BIAS
1.32Vpp
AVSS
AIN+
1.5nF
AIN-
1.32Vpp_AIN-
AVSS
Fig.1 Input Buffer Circuit Example ( Differential input )
10k
Signal
10k
Vop
BIAS ^{0.1µ 4.7k}
10µ ⁺
4.7k
Vop
NJM2100
-
+
BIAS
330 _10µ+
330
Vop = VA+ = 3.3V
BIAS
AVSS
AIN+
3.3nF
AIN-
2.64Vp_Ap_IN-
AVSS
Fig.2 Input Buffer Circuit Example ( Single-Ended input )
The AK7750 can also receive single-ended analog signals. In this case, the analog signal is fed to the AIN-
input pin (FS = (VREFH – VREFL) x 0.8= 2.64 Vp-p at VREFH = 3.3 V, VREFL = 0.0 V), and a bias voltage
is fed to the AIN+ input pin. When 3.3 V OP amps are used in, low-saturation type OP amps are
recommended. An electrolytic capacitor connected to AIN+ pin is effective in lowering secondary
harmonics (refer to Figure 2).
5) Analog Output
The analog output is single-ended. Output range is 2.00 Vp-p (typ) centered on VCOM.
The Out-of-Band noise (shaping noise) generated by an internal delta-sigma modulator is attenuated by an
on-chip switched capacitor filter (SCF) and a continuous time filter (CTF). Therefore it is not necessary to
add an external filter for normal use. If ADC without anti-aliasing input filter is connected to DAC’s output
directly, the spurious noise may be appear. In this case, the insertion of low pass filter that has fo< 20kHz,
2^nd order (>12dB/oct) is effective.
The input code format is in 2’s complement. Positive full-scale output corresponds to 7FFFFFh (@ 24 Bit)
input code, Negative full scale is 800000h (@ 24 Bit) and VCOM voltage ideally is 000000h (@ 24 Bit).
6) Connection with Digital Circuit
In order to minimize noise caused by Digital circuits, use low voltage logic ICs to connect the digital outputs.
Recommended logic families are 74LV, 74LV-A, 74ALVC and 74AVC series ICs.
[MS0296-E-00]
75
2005/03