ADC574 Burr-Brown Corporation, ADC574 Datasheet - Page 7

• Manufacturer Part Number: ADC574
• Description: Microprocessor-compatible Analog-to-digital Converter
• Manufacturer: Burr-Brown Corporation

FIGURE 2. Unipolar Configuration.
for the 20V range) that causes the output code to be DB0 ON
(high). Adjust potentiometer R
toggling ON and OFF with all other bits OFF. Then adjust
full scale by applying an input voltage of nominal full-scale
value minus 3/2LSB, the value which should cause all bits
to be ON. This value is +9.9963V for the 10V range and
+19.9927V for the 20V range. Adjust potentiometer R
bits DB1-DB11 are ON and DB0 is toggling ON and OFF.
CALIBRATION PROCEDURE—BIPOLAR RANGES
If external adjustments of full-scale and bipolar offset are
not required, the potentiometers may be replaced by 50 ,
1% metal-film resistors.
If adjustments are required, connect the converter as shown
in Figure 3. The calibration procedure is similar to that
described above for unipolar operation, except that the offset
adjustment is performed with an input voltage which is
1/2LSB above the minus full-scale value (–4.9988V for the
TABLE II. ADC574A Control Line Functions.
100k
5V range, –9.9976V for the 10V range). Adjust R
PIN
DESIGNATION
CE (Pin 6)
CS (Pin 3)
R/C(Pin 5)
A
12/8 (Pin 2)
R
O
1
(Pin 4)
+V
–V
Common
CC
CC
Analog
100
100k
Analog
Unipolar
Input
Adjust
Offset
DEFINITION
Chip Enable
(active high)
Chip Select
(active low)
Read/Convert
(“1” = read)
(“0” = convert)
Byte Address
Short Cycle
Data Mode Select
(“1” = 12 bits)
(“0” = 8 bits)
R
2
100
Full-Scale
Adjust
Range
Range
10V
20V
10
12
13
14
8
9
1
until DB0 is alternately
Must be high (“1”) to either initiate a conversion or read output data. 0-1 edge may be used to initiate a conversion.
Must be low (“0”) to either initiate a conversion or read output data. 1-0 edge may be used to initiate a conversion.
Must be low (“0”) to initiate either 8- or 12-bit conversions. 1-0 edge may be used to initiate a conversion.
Must be high (“1”) to read output data. 0-1 edge may be used to initiate a read operation.
In the start-convert mode, A
in two 8-bit bytes, A
When reading output data, 12/8 = “1” enables all 12 output bits simultaneously. 12/8 = “0” will enable the MSBs
or LSBs as determined by the A
Ref In
Ref Out
Bipolar Offset
Comparator
ADC574A
O
= “0” accesses 8 MSBs (high byte) and A
2
1
until
O
for
selects 8-bit (A
O
line.
7
FIGURE 3. Bipolar Configuration.
DB0 to toggle ON and OFF with all other bits OFF. To
adjust full-scale, apply a DC input signal which is 3/2LSB
below the nominal plus full-scale value (+4.9963V for 5V
range, +9.9927V for 10V range) and adjust R
toggle ON and OFF with all other bits ON.
CONTROLLING THE ADC574A
The Burr-Brown ADC574A can be easily interfaced to most
microprocessor systems and other digital systems. The mi-
croprocessor may take full control of each conversion, or the
converter may operate in a stand-alone mode, controlled
only by the R/C input. Full control consists of selecting an
8- or 12-bit conversion cycle, initiating the conversion, and
reading the output data when ready—choosing either 12 bits
all at once, or 8 bits followed by 4 bits in a left-justified
format. The five control inputs (12/8, CS, A
are all TTL/CMOS-compatible. The functions of the control
inputs are described in Table II. The control function truth
table is listed in Table III.
O
Full-Scale Adjust
FUNCTION
= “1”) or 12-bit (A
Analog
Input
Bipolar
Offset
Adjust
Common
Analog
R
2
R
1
100
O
100
O
= “1” accesses 4 LSBs and trailing “0s” (low byte).
Range
Range
= "0") conversion mode. When reading output data
10V
20V
10
12
13
14
8
9
ADC574A
Ref In
Ref Out
Bipolar Offset
Comparator
O
, R/C, and CE)
ADC574A
2
for DB0 to
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