EVAL-AD7934CB View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'EVAL-AD7934CB' PDF : 32 Pages View PDF
PARALLEL INTERFACE
The AD7933/AD7934 have a flexible, high speed, parallel
interface. This interface is 10 bits (AD7933) or 12 bits (AD7934)
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 also 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 t1. This
must happen after the 14th falling edge of CLKIN; otherwise, the
conversion is aborted and the track-and-hold goes back into track.
AD7933/AD7934
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 10 bits or 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 13th rising edge of CLKIN
after this (see Figure 34). When operating the device in
autoshutdown or autostandby mode, where the ADC powers
down at the end of each conversion, a rising edge on the
CONVST signal is used to power up the device.
CONVST
CLKIN
BUSY
INTERNAL
TRACK/HOLD
tCONVERT
12
34 5
t2
t3
B
t1
A
12 13 14
t20
t9
tACQUISITION
CS
RD
DB0 TO DB11
THREE-STATE
t10
t12
t11
t13
t14
DATA
THREE-STATE
tQUIET
WITH CS AND RD TIED LOW
DB0 TO DB11
OLD DATA
DATA
Figure 34. AD7933/AD7934 Parallel Interface—Conversion and Read Cycle Timing in Word Mode (W/B = 1)
Rev. B | Page 23 of 32
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