AK5578EN Datasheet, PDF (66/70 Pages) Asahi Kasei Microsystems – 8-Channel Differential 32-bit  ADC

[AK5578]
1. Grounding and Power Supply Decoupling
The AK5578 requires careful attention to power supply and grounding arrangements. Normally AVDD1/2
and TVDD are supplied from analog supply of the system. The power-up sequence between AVDD1/2
and TVDD are not critical when AVDD1/2 and TVDD are supplied separately. DVSS and AVSS1/2 must
be connected to the same analog ground plane. System analog ground and digital ground should be
wired separately and connected together as close as possible to where the supplies are brought onto the
printed circuit board. Decoupling capacitors for high frequency should be placed as near as possible to
the supply pin.
2. Reference Voltage
The differential voltage between the VREFH1-4 pins and the VREFL1-4 pins are the common voltage of
A/D conversion. The VREFL1-4 pins are normally connected to AVSS. In order to remove a high
frequency noise, connect a 20 Ω resistor between the VREFH1-4 pins and analog 5 V supply, and
connect a 0.1 μF ceramic capacitor in parallel with an 100 μF electrolytic capacitor between the
VREFH1-4 pins and the VREFL1-4 pins. Especially the ceramic capacitor should be connected as close
as possible to the pin. All digital signals, especially clocks, should be kept away from the VREFH1-4 pins
and VREFL1-4 pins in order to avoid unwanted noise coupling into the AK5578.
3. Analog Inputs
The Analog input signal is differentially supplied into the modulator via the AINn+ and the AINn- pins (n=
1-8). The input voltage is the difference between the ALINn+ and ALINn- pins (n= 1-8). The full scale
signal on each pin is nominally ±2.8 V (typ). A voltage from AVSS1/2 to AVDD1/2 can be input to the
AK5578. The output code format is two’s complement. The internal HPF removes DC offset (including
DC offset by the ADC itself).
The AK5578 requires a +5 V analog supply voltage. Any voltage which exceeds the upper limit of
AVDD1/2+0.3 V and lower limit of AVSS1/20.3 V and any current beyond 10 mA for the analog input
pins 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 ±15 V for
other analog circuits in the system.
015016736-E-00
- 66 -
2015/12