ADS7825_14 Datasheet, PDF (7/22 Pages) Texas Instruments – 4 Channel, 16-Bit Sampling CMOS A/D Converter

BASIC OPERATION
PARALLEL OUTPUT
Figure 1a shows a basic circuit to operate the ADS7825 with
parallel output (Channel 0 selected). Taking R/C (pin 22)
LOW for 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 updated. If BYTE (pin
21) is LOW, the 8 most significant bits will be valid when
pin 24 rises; if BYTE is HIGH, the 8 least significant bits
will be valid when BUSY rises. Data will be output in
Binary Two’s Complement 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 commands will be ignored while BUSY is
LOW.
The ADS7825 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.
SERIAL OUTPUT
Figure 1b shows a basic circuit to operate the ADS7825 with
serial output (Channel 0 selected). Taking R/C (pin 22)
LOW for 40ns (12µs max) will initiate a conversion and
output valid data from the previous conversion on SDATA
(pin 16) synchronized to 16 clock pulses output on
DATACLK (pin 15). BUSY (pin 24) will go LOW and stay
LOW until the conversion is completed and the serial data
has been transmitted. Data will be output in Binary Two’s
Complement 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 ADS7825 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.
Parallel Output
(a)
1
±10V
2
3
28
0.1µF 10µF
27
+
+ ^+5V
26
+
2.2µF
+
2.2µF
4
25
5
24
6
23
7
22
ADS7825
8
21
9
20
BUSY
Convert Pulse
R/C
BYTE
40ns min
+5V⁽¹⁾
10
19
11
18
12
17
13
16
14
15
Pin 21 D15 D14 D13 D12 D11
LOW
Pin 21 D7 D6 D5 D4 D3
HIGH
NOTE: (1) PAR/SER = 5V
D10 D9 D8
D2 D1 D0
±10V
Serial Output
1
28
2
27
3
26
4
25
5
24
+
2.2µF
+
2.2µF
6
23
7
22
ADS7825
8
21
NC⁽²⁾ 9
20
NC⁽²⁾ 10
19
NC⁽²⁾ 11
18
EXT/INT
12
17
SYNC
13
16
14
15
NOTES: (1) DATACLK (pin 15) is an output when EXT/INT (pin 12) is LOW
and an input when EXT/INT is HIGH. (2) NC = no connection. (3) PAR/SER = 0V.
FIGURE 1. Basic Connection Diagram, (a) Parallel Output, (b) Serial Output.
(b)
0.1µF 10µF
+
+ ^+5V
BUSY
Convert Pulse
R/C
40ns min
(3)
SDATA
DATACLK⁽¹⁾
®
7
ADS7825