AD7938-6 Analog Devices, AD7938-6 Datasheet - Page 23

• Manufacturer Part Number: AD7938-6
• Description: 8-Channel, 625 kSPS, 12-Bit Parallel ADCs with a Sequencer
• Manufacturer: Analog Devices

Specifications of AD7938-6

• Resolution (bits): 12bit
• # Chan: 8
• Sample Rate: 625kSPS
• Interface: Par
• Analog Input Type: Diff-Uni,SE-Uni
• Ain Range: Uni (Vref),Uni (Vref) x 2
• Adc Architecture: SAR
• Pkg Type: CSP,QFP

Data Sheet
PARALLEL INTERFACE
The AD7938-6 has a flexible, high speed, parallel interface. This
interface is 12-bits wide and is capable of operating in either
word (W/ B tied high) or byte (W/ B tied low) mode. The
CONVST signal is used to initiate conversions, and when
operating in autoshutdown or autostandby mode, it is used to
initiate power-up.
A falling edge on the CONVST signal is used to initiate
conversions and it puts the ADC track-and-hold into track.
Once the CONVST signal goes low, the BUSY signal goes high
for the duration of the conversion. In between conversions,
CONVST must be brought high for a minimum time of t
must happen after the 14
conversion is aborted and the track-and-hold goes back into track.
TRACK/HOLD
DB0 TO DB11
DB0 TO DB11
INTERNAL
CONVST
CLKIN
BUSY
th
falling edge of CLKIN; otherwise, the
RD
CS
Figure 35. AD7938-6 Parallel Interface—Conversion and Read Cycle Timing in Word Mode (W/ B = 1)
WITH CS AND RD TIED LOW
t
2
t
3
1
2
THREE-STATE
OLD DATA
3
4
1
. This
t
CONVERT
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5
12
A
At the end of the conversion, BUSY goes low and can be used to
activate an interrupt service routine. The CS and RD lines are
then activated in parallel to read the 12 bits of conversion data.
When power supplies are first applied to the device, a rising
edge on CONVST is necessary to put the track-and-hold into
track. The acquisition time of 125 ns minimum must be allowed
before CONVST is brought low to initiate a conversion. The
ADC then goes into hold on the falling edge of CONVST and
back into track on the 13
Figure 35
autostandby mode, where the ADC powers down at the end of
each conversion, a rising edge on the
power up the device.
13
t
B
10
t
9
14
). When operating the device in autoshutdown or
t
20
t
13
t
12
t
DATA
DATA
ACQUISITION
t
1
th
rising edge of CLKIN after this (see
THREE-STATE
t
t
11
14
t
QUIET
CONVST signal is used to
AD7938-6