AK5367 Datasheet, PDF (26/28 Pages) Asahi Kasei Microsystems – 96kHz 24-Bit ΔΣ ADC with 0V Bias Selector

[AK5367]
1. Grounding and Power Supply Decoupling
The AK5367 requires careful attention to power supply and grounding arrangements. AVDD, DVDD and CVDD are
usually supplied from the analog supply in the system. Alternatively if AVDD, DVDD and CVDD are supplied
separately, the power up sequence is not critical. VSS1 and VSS2 of the AK5367 must be connected to analog ground
plane. System analog ground and digital ground should be connected together near to where the supplies are brought onto
the printed circuit board. Decoupling capacitors should be as near to the AK5367 as possible, with the small value
ceramic capacitor being the closest.
2. Voltage Reference Inputs
The differential voltage between AVDD and VSS1 sets the analog input range. VCOM is a signal common of this chip.
An electrolytic capacitor 2.2µF parallel with a 0.1µF ceramic capacitor attached to VCOM pin eliminates the effects of
high frequency noise. No load current may be drawn from the VCOM pin. All signals, especially clocks, should be kept
away from VCOM pins in order to avoid unwanted coupling into the AK5367.
3. Analog Inputs
An analog input of AK5367 is single-ended input to Pre-Amp through the external resistor. For input signal range, adjust
feedback resistor so that Pre-Amp output may become the input range (typ. 0.6 x AVDD Vpp) of ADC (LISEL,RISEL
pin). Between the Pre-Amp output (LOUT, ROUT pin) and the ADC input (LISEL,RISEL pin) is AC coupled with
capacitor. When the impedance of LISEL/RISEL pins is “R” and the capacitor of between the Pre-Amp output and the
ADC input is “C”, the cut-off frequency is fc = 1/(2πRC). The ADC output data format is 2’s compliment. The internal
HPF removes the DC offset. The AK5367 samples the analog inputs at 64fs. The digital filter rejects noise above the stop
band except for multiples of 64fs. The AK5367 includes an anti-aliasing filter (RC filter) to attenuate a noise around 64fs.
4. Attention to the PCB Wiring
LIN1-4 and RIN1-4 pins are the summing nodes of the Pre-Amp. Attention should be given to avoid coupling with other
signals on those nodes. This can be accomplished by making the wire length of the input resistors as short as possible. The
same theory also applies to the LOPIN/ROPIN pins and feedback resistors; keep the wire length to a minimum. Unused
input pins among LIN1-4 and RIN1-4 pins should be left open. When external devices are connected to LOUT and ROUT
pin, the input impedance is min. 15kΩ.
4. I²C bus Connection
SCL and SDA pins should be connected to DVDD through the resistor based on I²C standard. As there is a protection
between each pin and DVDD, the pulled up voltage mast be DVDD or lower(Figure 25).
+3.3V
DVDD
AK5367
SDA pin
VSS2
Figure 25. SDA pin output
MS0694-E-00
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2007/12