AK8456 Datasheet, PDF (20/32 Pages) Asahi Kasei Microsystems – 3 channel input 16bit 30MSPS Video ADC with LED driver

[AK8456]
 CIS Signal Input Channel Number Select
There are 3-channel mode and 1-channel mode as input channel number. Input channel
number is selected by register. In 1-channel mode, signal is input to CISIN0. At this time,
CISIN1 and CISIN2 can be connected to AVSS, or opened, or input dummy signal. Sample
and hold circuit and DAC of not used channels are power down.
Frequency of ADCK in 3-channel mode is three times the pixel frequency per channel. In
1-channel mode, ADCK frequency is equal the pixel frequency.
 CIS Reference Voltage
It is able to select to use internal voltage or to use externally input voltage as sensor
reference voltage by register. Input range of external voltage is from 0.8V to 1.2V. Internal
voltage is 1.0V (typ.) or 1.1V (typ.).
 Offset Adjustment
Offset adjustment is done by adding DAC output voltage to sensor signal. Resolution of
DAC is six bit, range is 369mV(typ.)/300mV(min.) in equivalent input voltage. 50mV
(max.) out of 369mV is used to cancel LSI internal offset. Therefore effective range for
correcting signal offset is 319mV(typ.)/250mv(min.).
The equivalent input voltage does not change even if set 6dB gain at sample and hold block.
VDC
Offset DAC
Vref
S/H
CISINn
Signal
Vsig
Reference
Vref
GND
Internal
Reference
Level
Vsig
+Max.(011111b)
369mV
369mV
Max.(100001b)
 Sampling
Fig.22 Offset adjustment
Sensor signal are sampled at SHD falling edge.
 Gain Adjustment
It is possible to amplify signals at sample and hold block. And it is possible to amplify A/D
output code by digital PGA. Gain of digital PGA is from 0dB to 18dB. Its resolution is 8bit.
 Output Format
Output Formal is straight binary. Gray code output is possible too.
014002433-E-00
- 20 -
2014/06