AK5394A Datasheet, PDF (18/24 Pages) Asahi Kasei Microsystems – Super High Performance 192kHz 24-Bit ADC

ASAHI KASEI
[AK5394A]
1. Grounding and Power Supply Decoupling
The AK5394A requires careful attention to power supply and grounding arrangements. Analog ground and digital ground
of the system should be separate and connected together near to where the supplies are brought onto the printed circuit
board. Decoupling capacitors should be as near to the AK5394A as possible, with the small value ceramic capacitor being
the nearest.
2. On-chip Voltage Reference and VCOM
The reference voltage for A/D converter is supplied from VREF+/− pin at AGND reference. A 0.22µF ceramic capacitor
should be attached between VREF+ and VREF−. An electrolytic capacitor (<1000µF) should be connected between
AGND and VREF+/− respectively to eliminate the effects of low frequency noise. Especially a ceramic capacitor should
be as near to the pins as possible. And all digital signals, especially clocks, should be kept away from the VREF+/− pins in
order to avoid unwanted coupling into the AK5394A. No load current may be taken from the VREF+/− pins.
VCOM is a common voltage of the analog signal. In order to eliminate the effects of high frequency noise, a 0.22µF
ceramic capacitor should be connected as near to the VCOM pin as possible. And all signals, especially clocks, should be
kept away from the VCOM pin in order to avoid unwanted coupling into the AK5394A. No load current may be drawn
from the VCOM pin.
3. Analog Inputs
Analog signal is differentially input into the modulator via the AIN+ and the AIN− pins. The input voltage is the difference
between AIN+ and AIN− pins. The full-scale of each pin is nominally ±2.4Vpp (typ). The AK5394A can accept input
voltages from AGND to VA. The ADC output data format is 2’s complement. The output code is 7FFFFFH (@24bit) for
input above a positive full scale and 800000H (@24bit) for input below a negative full scale. The ideal code is 000000H
(@24bit) with no input signal. The DC offset is removed by the offset calibration.
The AK5394A samples the analog inputs at 128fs (6.144MHz@fs=48kHz, Normal Speed Mode). The digital filter rejects
noise above the stop band except for multiples of 128fs. A simple RC filter may be used to attenuate any noise around
128fs and most audio signals do not have significant energy at 128fs.
The AK5394A accepts +5V supply voltage. Any voltage which exceeds the upper limit of VA+0.3V and lower limit of
AGND−0.3V and any current beyond 10mA for the analog input pins (AIN+/−) should be avoided. Excessive currents to
the input pins may damage the device. Hence input pins must be protected from signals at or beyond these limits. Use
caution specially in case of using ±15V in other analog circuits.
MS0137-E-01
- 18 -
2002/07