AD7798/AD7799
Data Sheet
Rev. B | Page 6 of 28
TIMING CHARACTERISTICS
AVDD = 2.7 V to 5.25 V, DVDD = 2.7 V to 5.25 V, GND = 0 V, Input Logic 0 = 0 V, Input Logic 1 = DVDD, unless otherwise noted.
Table 2.
Limit at TMIN, TMAX (B Version)
Unit
Conditions/Comments
t3
100
ns min
SCLK high pulse width
t4
100
ns min
SCLK low pulse width
Read Operation
t1
0
ns min
CS falling edge to DOUT/RDY active time
60
ns max
DVDD = 4.75 V to 5.25 V
80
ns max
DVDD = 2.7 V to 3.6 V
0
ns min
SCLK active edge to data valid d
elay460
ns max
DVDD = 4.75 V to 5.25 V
80
ns max
DVDD = 2.7 V to 3.6 V
10
ns min
Bus relinquish time after CS inactive edge
80
ns max
t6
0
ns min
SCLK inactive edge to CS inactive edge
t7
10
ns min
SCLK inactive edge to DOUT/RDY high
Write Operation
t8
0
ns min
CS falling edge to SCLK active edge setup t
ime4t9
30
ns min
Data valid to SCLK edge setup time
t10
25
ns min
Data valid to SCLK edge hold time
t11
0
ns min
CS rising edge to SCLK edge hold time
1
Sample tested during initial release to ensure compliance. All input signals are specified with tR = tF = 5 ns (10% to 90% of DVDD) and timed from a voltage level of 1.6 V.
2
3
These times are measured with the load circuit of Figure 2 and defined as the time required for the output to cross the VOL or VOH limits. 4
SCLK active edge is the falling edge of SCLK.
5
These times are derived from the measured time taken by the data output to change 0.5 V when loaded with the circuit o
f Figure 2. The measured time is then
extrapolated back to remove the effects of charging or discharging the 50 pF capacitor. This means that the times quoted in the timing characteristics are the true bus
relinquish times of the part and, as such, are independent of external bus loading capacitances.
6
RDY returns high after a read of the ADC. In single-conversion mode and continuous-conversion mode, data can be reread, if required, while RDY is high, but care
should be taken to ensure that subsequent reads do not occur close to the next output update. In continuous read mode, the digital word can be read only once.
ISINK (1.6mA WITH DVDD = 5V,
100A WITH DVDD = 3V)
ISOURCE (200A WITH DVDD = 5V,
100A WITH DVDD = 3V)
1.6V
TO
OUTPUT
PIN
50pF
04856-
002
Figure 2. Load Circuit for Timing Characterization