ak5365 AKM Semiconductor, Inc., ak5365 Datasheet - Page 39

• Manufacturer Part Number: ak5365
• Description: 24-bit 96khz ?? Adc With Selector/pga/alc
• Manufacturer: AKM Semiconductor, Inc.

[AK5365
ASAHI KASEI
]
1. Grounding and Power Supply Decoupling
The AK5365 requires careful attention to power supply and grounding arrangements. AVDD and DVDD are usually
supplied from the analog supply in the system. Alternatively if AVDD and DVDD are supplied separately, the power up
sequence is not critical. AVSS and DVSS of the AK5365 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 AK5365 as possible, with the small value ceramic capacitor being
the closest.
2. Voltage Reference Inputs
The differential voltage between AVDD and AVSS sets the analog input range. VCOM is a signal ground 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 the VREF and VCOM pins in order to avoid unwanted coupling into the AK5365.
3. Analog Inputs
An analog input of AK5365 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. 0.2 x AVDD Vrms) of IPGA (IPGAL, IPGAR
pin). Between the Pre-Amp output (LOUT, ROUT pin) and the IPGA input (IPGAL, IPGAR pin) is AC coupled with
capacitor. When the impedance of IPGAL/R pins is “R” and the capacitor of between the Pre-Amp output and the IPGA
input is “C”, the cut-off frequency is fc = 1/(2 RC).
The ADC output data format 2’s compliment. The internal HPF removes the DC offset.
The AK5365 samples the analog inputs at 64fs. The digital filter rejects noise above the stop band except for multiples of
64fs. The AK5365 includes an anti-aliasing filter (RC filter) to attenuate a noise around 64fs.
4. Attention to the PCB Wiring
LIN1-5 and RIN1-5 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 LIN1-5 and RIN1-5 pins should be left open.
When external devices are connected to LOUT and ROUT pin, the input impedance of an external device which the LOUT
and ROUT pins can drive is min 6.3k .
MS0164-E-01
2002/08
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