AKD4620B-B_06 Datasheet, PDF (10/63 Pages) Asahi Kasei Microsystems – 24Bit A/D & D/A converter

ASAHI KASEI
[AKD4620B-B]
„ Analog Input Buffer Circuit
1. Differential Input Mode
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). Figure 3 shows an input buffer circuit example. This is a fully differential input buffer
circuit with an inverted amplifier (fc=370KHz,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.
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
AK4620B
22
AIN-
2.82Vpp
Figure 3. Input buffer circuit in differential mode
2. Single-ended Input Mode
When the AK4620B is evaluated by single-ended mode, C49 and C90 should be removed.
3.07Vpp
22u
Signal
+
22u
Signal
+
AK4620B
2 AINR+
3 AINR-
4 AINL+
5 AINL-
Figure 4. Input buffer circuit in Single-ended mode
<KM078901>
- 10 -
2006/06