AK5397 Datasheet, PDF (38/44 Pages) Asahi Kasei Microsystems – 32-Bit Stereo Premium ADC

[AK5397]
1. Grounding and Power Supply Decoupling
The AK5397 requires careful attention to power supply and grounding arrangements. To minimize digital
noise coupling, AVDD and DVDD should be individually de-coupled at the AK5397. AVDD is usually
supplied from analog supply in system and DVDD is supplied from digital supply in system. Power lines
of AVDD and DVDD should be distributed separately from the point with low impedance of regulator etc.
AVSS and DVSS must be connected to the same analog ground plane. Decoupling capacitors for high
frequency should be placed as near as possible to the supply pin.
2. Voltage Reference Inputs
The reference voltage for A/D converter is the difference between VREFHL/R pin and VREFLL/R pin.
VREFLL/R pins are connected to AVSS and an electrolytic capacitor over 10µF parallel with a 0.1µF
ceramic capacitor between the VREFHL/R pin and the VREFLL/R pin eliminates the effects of high
frequency noise. It is important that a ceramic capacitor should be as near to the pins as possible. All
digital signals, especially clocks, should be kept away from the VREFHL/R and VREFLL/R pins in order
to avoid unwanted coupling into the AK5397.
VCOM is a signal ground of this chip. A 10µF electrolytic capacitor in parallel with a 0.1µF ceramic
capacitor attached to the 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 VCOM pin in
order to avoid unwanted coupling into the AK5397.
3. Analog Inputs
The Analog input signal is differentially supplied into the modulator via the LIN+ (RIN+) and the LIN-
(RIN-) pins. The input voltage is the difference between the LIN+ (RIN+) and LIN- (RIN-) pins. The full
scale signal on each pin is nominally ±2.80V (typ). The output code format is two’s complement. The
output voltage (VAOUT) is positive full scale for 7FFFFFFFH (@32bit) and negative full scale for
80000000H (@32bit). The ideal VAOUT is 0V for 00000000H (@32bit). The internal HPF removes DC
offset.
The AK5397 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. The AK5397 includes an
anti-aliasing filter (RC filter) to attenuate a noise around 128fs.
The AK5397 requires a +5V analog supply voltage. Any voltage which exceeds the upper limit of
AVDD+0.3V and lower limit of AVSS-0.3V and any current beyond 10mA for the analog input pins
(LIN+/-, RIN+/-) 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 especially when using
±15V for other analog circuits in the system.
014011535-E-00
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2014/11