AK5388_09 Datasheet, PDF (25/31 Pages) Asahi Kasei Microsystems – 120dB 24-bit 192kHz 4-Channel ADC

Digital Ground
Analog Ground
[AK5388]
System
Controller
1 LIN1+
2 LIN1-
3 VSS1
4 AVDD1
5 TEST1
6 VSS2
7 CKS0
8 CKS1
9 CKS2
10 PDN
11 M/SN
RIN2+ 33
RIN2- 32
VSS6 31
AVDD2 30
TEST2 29
VSS5 28
VSS4 27
DVDD2 26
HPFE 25
MONO 24
DIF 23
Figure 22. Ground Layout
Note: VSS1-6 must be connected to the same analog ground plane.
1. Grounding and Power Supply Decoupling
The AK5388 requires careful attention to power supply and grounding arrangements. AVDD1/2 and DVDD1/2 are
usually supplied from the system’s analog supply. Alternatively if AVDD1/2 and DVDD1/2 are supplied separately, the
power up sequence is not critical. VSS1-6 of the AK5388 must be connected to the 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 AK5388 as possible, with the small value ceramic capacitor
being the nearest.
2. Voltage Reference Inputs
The reference voltage for A/D converter is supplied from VREFP1/2 pins at VREFL1/2 reference. VREFL1/2 pins are
connected to analog ground and an electrolytic capacitor over 10μF parallel with a 0.1μF ceramic capacitor between the
VREFP1/2 pins and the VREFL1/2 pins eliminate 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
VREFP1/2 pins in order to avoid unwanted coupling into the AK5388.
VCOM1/2 is a signal ground for this device. An electrolytic capacitor (2.2µF typical) attached to the VCOM1/2 pins
eliminates the effects of high frequency noise. It is important that a ceramic capacitor should be as near to the pins as
possible. No load current may be drawn from the VCOM1/2 pins. All signals, especially clocks, should be kept away
from the VCOM1/2 pins in order to avoid unwanted coupling into the AK5388.
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 ±2.8Vpp(typ). The AK5388 can accept input voltages from VSS1-6 to AVDD1/2. The ADC output data
format is two’s complement. The internal HPF removes DC offset.
The AK5388 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 AK5388 includes an anti-aliasing filter (RC filter) to
attenuate a noise around 128fs.
The AK5388 requires a +5V analog supply voltage. Any voltage which exceeds the upper limit of AVDD1/2+0.3V and
lower limit of VSS1-6 − 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.
MS1096-E-01
- 25 -
2009/08