ADS7807 Burr-Brown Corporation, ADS7807 Datasheet - Page 8

• Manufacturer Part Number: ADS7807
• Description: Low-Power 16-Bit Sampling CMOS ANALOG-to-DIGITAL CONVERTER
• Manufacturer: Burr-Brown Corporation

The ADS7807 will begin tracking the input signal at the end
of the conversion. Allowing 25 s between convert com-
mands assures accurate acquisition of a new signal. Refer to
Tables III and IV for a summary of CS, R/C, and BUSY
states and Figures 2 through 6 for timing diagrams.
Table III. Control Functions When Using Parallel Output
Table V. Output Codes and Ideal Input Voltages.
Table IV. Control Functions When Using Serial Output.
NOTE: (1) See Figures 2 and 3 for constraints on data valid from
conversion “n-1”.
NOTE: (1) See Figures 4, 5, and 6 for constraints on data valid from conversion “n-1”.
DESCRIPTION
Full-Scale Range
Least Significant Bit (LSB)
+Full Scale (FS – 1LSB)
Midscale
One LSB Below Midscale
–Full Scale
CS
1
0
0
0
0
X
CS
0
0
0
0
X
R/C
X
X
0
1
1
1
0
(DATACLK tied LOW, EXT/INT tied HIGH).
R/C
0
0
1
1
0
X
®
BUSY
X
1
1
1
0
0
0
ADS7807
BUSY
OPERATION
None. Databus is in Hi-Z state.
Initiates conversion “n”. Databus remains
in Hi-Z state.
Initiates conversion “n”. Databus enters Hi-Z
state.
Conversion “n” completed. Valid data from
conversion “n” on the databus.
Enables databus with valid data from
conversion “n”.
Enables databus with valid data from
conversion “n-1”
Enables databus with valid data from
conversion “n-1”
New conversion initiated without acquisition
of a new signal. Data will be invalid. CS and/or
R/C must be HIGH when BUSY goes HIGH.
New convert commands ignored. Conversion
“n” in progress.
1
1
1
1
1
0
0
0
EXT/INT
9.999695V
–305 V
305 V
–10V
0
0
1
1
1
1
1
X
X
0V
10
(1)
(1)
. Conversion n in progress.
. Conversion “n” in progress.
DATACLK
ANALOG INPUT
Output
Output
Input
Input
Input
Input
Input
X
X
4.999924V
2.499924V
0V to 5V
76 V
2.5V
0V
OPERATION
Initiates conversion “n”. Valid data from conversion “n-1” clocked out on SDATA.
Initiates conversion “n”. Valid data from conversion “n-1” clocked out on SDATA.
Initiates conversion “n”. Internal clock still runs conversion process.
Initiates conversion “n”. Internal clock still runs conversion process.
Conversion “n” completed. Valid data from conversion “n” clocked out on SDATA synchronized
to external data clock.
Valid data from conversion “n-1” output on SDATA synchronized to external data clock.
Conversion “n” in progress.
Valid data from conversion “n-1” output on SDATA synchronized to external data clock.
Conversion “n” in progress.
New conversion initiated without acquisition of a new signal. Data will be invalid. CS and/or R/C
must be HIGH when BUSY goes HIGH.
New convert commands ignored. Conversion “n” in progress.
3.999939V
1.999939V
0V to 4V
61 V
2V
0V
8
CS and R/C are internally OR’d and level triggered. There
is not a requirement which input goes LOW first when
initiating a conversion. If, however, it is critical that CS or
R/C initiates conversion ‘n’, be sure the less critical input is
LOW at least 10ns prior to the initiating input. If EXT/INT
(pin 8) is LOW when initiating conversion ‘n’, serial data
from conversion ‘n-1’ will be output on SDATA (pin 19)
following the start of conversion ‘n’. See Internal Data
Clock in the Reading Data section.
To reduce the number of control pins, CS can be tied LOW
using R/C to control the read and convert modes. This will
have no effect when using the internal data clock in the serial
output mode. However, the parallel output and the serial
output (only when using an external data clock) will be
affected whenever R/C goes HIGH. Refer to the Reading
Data section.
READING DATA
The ADS7807 outputs serial or parallel data in Straight
Binary or Binary Two’s Complement data output format. If
SB/BTC (pin 7) is HIGH, the output will be in SB format,
and if LOW, the output will be in BTC format. Refer to
Table V for ideal output codes.
The parallel output can be read without affecting the internal
output registers; however, reading the data through the serial
BINARY TWO’S COMPLEMENT
0111 1111 1111 1111
0000 0000 0000 0000
1111 1111 1111 1111
1000 0000 0000 0000
BINARY CODE
(SB/BTC LOW)
DIGITAL OUTPUT
CODE
7FFF
FFFF
8000
HEX
0000
1111 1111 1111 1111
1000 0000 0000 0000
0111 1111 1111 1111
0000 0000 0000 0000
BINARY CODE
STRAIGHT BINARY
(SB/BTC HIGH)
CODE
7FFF
HEX
8000
0000
FFFF