SPECIFIC FUNCTION
CS
R/C
BUSY EXT/INT DATACLK PWRD SB/BTC
OPERATION
Initiate Conversion and
Output Data Using
Internal Clock
1>0
0
1
0
Output
0
x
Initiates conversion “n”. Data from conversion “n–1”
clocked out on DATA synchronized to 12 clock
pulses output on DATACLK.
0
1>0
1
0
Output
0
x
Initiates conversion “n”. Data from conversion “n–1”
clocked out on DATA synchronized to 12 clock
pulses output on DATACLK.
Initiate Conversion and
Output Data Using External
Clock
1>0
0
0
1>0
1
1
1
1
1
1
1
Input
Input
Input
0
0
x
x
x
x
Initiates conversion “n”.
Initiates conversion “n”.
1>0
Outputs a pulse on SYNC followed by data from
conversion “n” clocked out synchronized to external
DATACLK.
1>0
0
1
0>1
0
0
0
1
1
x
Input
Input
x
0
0
0
x
x
x
Outputs a pulse on SYNC followed by data from
conversion “n–1” clocked out synchronized to
external DATACLK.(1) Conversion “n” in process.
Outputs a pulse on SYNC followed by data from
conversion “n–1” clocked out synchronized to
external DATACLK .(1) Conversion “n” in process.
Incorrect Conversions
Power Down
0
0>1
CS or R/C must be HIGH or a new conversion will
be initiated without time for acquisition.
x
x
x
x
x
x
x
x
x
x
0
1
x
x
Analog circuitry powered. Conversion can proceed.
Analog circuitry disabled. Data from previous
conversion maintained in output registers.
x
x
x
x
x
x
x
x
x
x
x
x
0
1
Serial data is output in Binary Two’s Complement
format.
Selecting Output Format
Serial data is output in Straight Binary format.
NOTE: (1) See Figure 3b for constraints on previous data valid during conversion.
Table III. Control Truth Table.
DIGITAL OUTPUT
BINARY TWO’S
COMPLEMENT
(SB/BTC LOW)
STRAIGHT BINARY
(SB/BTC HIGH)
HEX
HEX
DESCRIPTION
ANALOG INPUT
BINARY CODE
CODE
BINARY CODE CODE
Full-Scale Range
Least Significant Bit (LSB)
+Full Scale (FS – 1LSB)
Midscale
±10
±5
±3.33V
0V to 5V 0V to 10V
1.22mV 2.44mV
0V to 4V
0.98mV
4.88mV
2.44mV
1.63mV
9.99512V 4.99756V 3.33171V 4.99878V 9.99756V
0V 0V 0V 2.5V 5V
–4.88mV –2.44mV –1.63mV 2.49878V 4.99756V
–10V –5V –3.333333V 0V 0V
3.99902V 0111 1111 1111
2V 0000 0000 0000
1.99902V 1111 1111 1111
0V 1000 0000 0000
7FF
000
FFF
800
1111 1111 1111
FFF
1000 0000 0000 800
0111 1111 1111 7FF
0000 0000 0000 000
One LSB Below Midscale
–Full Scale
Table IV. Output Codes and Ideal Input Voltages.
ADS7808
6
SBAS018A
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