ak4620b AKM Semiconductor, Inc., ak4620b Datasheet - Page 37

• Manufacturer Part Number: ak4620b
• Description: 24-bit 192khz Audio Codec With Ipga
• Manufacturer: AKM Semiconductor, Inc.

ASAHI KASEI
4. Analog Inputs
MS0401-E-00
4-1. Single-ended Input (ADMODE pin = “L”)
4-2. Full-Differential Input (ADMODE pin = “H”)
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 AK4620B includes an anti-aliasing
filter (RC filter) to attenuate noise around 128fs.
The AK4620B 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
10k
10k
9.3Vpp
VA
0.1µ
10µ
Figure 17. Input Buffer example in differential mode
4.7k
Bias
NJM5532
VA = 5V
VP+ = 15V
VP- = -15V
4.7k
VP+
VP-
47µ
47µ
3k
3k
- 37 -
Bias
Bias
470p
470p
910
910
22
22
2.82Vpp
10n
2.82Vpp
AIN+
AIN-
AK4620B
[AK4620B]
2005/07