AK4620A Datasheet, PDF (37/42 Pages) Asahi Kasei Microsystems – 24 BIT 192KHZ AUDIO CODEC WITH IPGA

ASAHI KASEI
[AK4620A]
4. Analog Inputs
4-1. Single-ended Input (ADMODE pin = “L”)
The IPGA inputs are single-ended. The input resistance of IPGA is typically 5.1kΩ at IPGA=0dB and typically
1.18kΩ at IPGA=+18dB. The input signal is typically AC coupled through a capacitor. The cut-off frequency is fc =
(1/2πRC). The input signal range scales with the VREF voltage and is nominally 3.07Vpp (VREF=5V) centered
around the internal common voltage (about VA/2). In single-ended mode, the AK4620A includes an anti-aliasing
filter (RC filter) to attenuate noise around 128fs.
4-2. Full-Differential Input (ADMODE pin = “H”)
The AK4620A can accept input voltages from AGND to VA. The input signal range scales with the VREF voltage
and is nominally 2.82Vpp (VREF = 5V), centered around the internal common voltage (about VA/2). Figure 17 shows
an input buffer circuit example. This is a fully differential input buffer circuit with an inverted amplifier (gain:
−10dB). The capacitor of 10nF between AINL+/− (AINR+/−) decreases the clock feedthrough noise of the modulator,
and composes a 1st order LPF (fc=360kHz) with a 22Ω resistor before the capacitor. This circuit also has a 1st order
LPF (fc=370kHz) composed of op-amp. The evaluation board should be referred about the detail.
Analog In
9.3Vpp
VA
10k
0.1µ 10µ
10k
910
4.7k
470p
4.7k
VP+ _{47µ 3k}
VP-
NJM5532
Bias
910
470p
47µ _3k
VA = 5V
Bias
VP+ = 15V
Bias
VP- = -15V
2.82Vpp
22
AIN+
10n
AK4620A
22
AIN-
2.82Vpp
Figure 17. Input Buffer example in differential mode
MS0368-E-00
- 37 -
2004/12