Datasheet

ADS7807
7
SBAS022D
www.ti.com
output valid data from the previous conversion on SDATA
(pin 19) synchronized to 16 clock pulses output on DATACLK
(pin 18).
BUSY (pin 24) will go LOW and stay LOW until the
conversion is completed and the serial data has been trans-
mitted. Data will be output in BTC format, MSB first, and will
be valid on both the rising and falling edges of the data clock.
BUSY going HIGH can be used to latch the data. All convert
commands will be ignored while
BUSY is LOW.
The ADS7807 will begin tracking the input signal at the end
of the conversion. Allowing 25µs between convert com-
mands assures accurate acquisition of a new signal.
The offset and gain are adjusted internally to allow external
trimming with a single supply. The external resistors compen-
sate for this adjustment and can be left out if the offset and
gain will be corrected in software (refer to the Calibration
section).
STARTING A CONVERSION
The combination of CS (pin 23) and R/C (pin 22) LOW for a
minimum of 40ns puts the sample-and-hold of the ADS7807
in the hold state and starts conversion ‘n’.
BUSY (pin 24) will
go LOW and stay LOW until conversion ‘n’ is completed and
the internal output register has been updated. All new con-
vert commands during
BUSY LOW will be ignored. CS and/
or
R/C must go HIGH before BUSY goes HIGH, or a new
conversion will be initiated without sufficient time to acquire
a new signal.
BASIC OPERATION
PARALLEL OUTPUT
Figure 1a shows a basic circuit to operate the ADS7807 with
a ±10V input range and parallel output. Taking
R/C (pin 22)
LOW for a minimum of 40ns (12µs max) will initiate a
conversion.
BUSY (pin 24) will go LOW and stay LOW until
the conversion is completed and the output register is up-
dated. If BYTE (pin 21) is LOW, the eight Most Significant
Bits (MSBs) will be valid when
BUSY rises; if BYTE is HIGH,
the eight Least Significant Bits (LSBs) will be valid when
BUSY rises. Data will be output in Binary Two’s Complement
(BTC) format.
BUSY going HIGH can be used to latch the
data. After the first byte has been read, BYTE can be toggled
allowing the remaining byte to be read. All convert com-
mands will be ignored while
BUSY is LOW.
The ADS7807 will begin tracking the input signal at the end
of the conversion. Allowing 25µs between convert com-
mands assures accurate acquisition of a new signal.
The offset and gain are adjusted internally to allow external
trimming with a single supply. The external resistors compen-
sate for this adjustment and can be left out if the offset and gain
will be corrected in software (refer to the Calibration section).
SERIAL OUTPUT
Figure 1b shows a basic circuit to operate the ADS7807 with
a ±10V input range and serial output. Taking
R/C (pin 22)
LOW for 40ns (12µs max) will initiate a conversion and
FIGURE 1a. Basic ±10V Operation, both Parallel and Serial
Output.
FIGURE 1b. Basic ±10V Operation with Serial Output.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
NC
(1)
NC
(1)
NC
(1)
NC
(1)
NC
(1)
28
27
26
25
24
23
22
21
20
19
18
17
16
15
ADS7807
Serial Output
200Ω
66.5kΩ
±10V
+5V
0.1µF
NC
(1)
NC
(1)
NC
(1)
10µF
+
+5V
+
100Ω
++
2.2µF
2.2µF
Convert Pulse
BUSY
40ns min
R/C
SDATA
DATACLK
NOTE: (1) These pins should be left unconnected.
They will be active when
R/C
is HIGH.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
ADS7807
Parallel Output
200Ω
66.5kΩ
±10V
+5V
0.1µF
NC
(1)
10µF
+
+5V
+
100Ω
B10 B9 B8
B2 B1 B0
(LSB)
B13 B12B15
(MSB)
Pin 21
LOW
B14 B11
B5 B4B7Pin 21
HIGH
B6 B3
2.2µF
++
2.2µF
Convert Pulse
BUSY
R/C
BYTE
40ns min
NOTE: (1) SDATA (pin 19) is always active.