AD565A/AD566A
FIGURE 6. OTHER VOLTAGE RANGES
Table I. Digital Input Codes
The AD566A can also be easily configured for a unipolar 0 volt
to +5 volt range or 2.5 volt and 10 volt bipolar ranges by
using the additional 5k application resistor provided at the 20
volt span R terminal, Pin 11. For a 5 volt span (0 V to +5 V or
2.5 V), the two 5k resistors are used in parallel by shorting Pin
11 to Pin 9 and connecting Pin 10 to the op amp output and the
bipolar offset resistor either to ground for unipolar or to VREF
for the bipolar range. For the 10 volt range (20 volt span) use
the 5k resistors in series by connecting only Pin 11 to the op
amp output and the bipolar offset connected as shown. The
10 volt option is shown in Figure 6.
DIGITAL INPUT
ANALOG OUTPUT
MSB
LSB
Straight Binary
Offset Binary
Twos Compl.*
0 0 0 0 0 0 0 0 0 0 0 0
0 1 1 1 1 1 1 1 1 1 1 1
1 0 0 0 0 0 0 0 0 0 0 0
1 1 1 1 1 1 1 1 1 1 1 1
Zero
–FS
Zero
Mid Scale – 1 LSB Zero – 1 LSB
+FS – 1 LSB
–FS
+1/2 FS
Zero
+FS – l LSB
+ FS – 1 LSB
Zero – 1 LSB
*Inverts the MSB of the offset binary code with an external inverter to obtain
twos complement.
R1
5k⍀
BIPOLAR OFF
20V SPAN
10V SPAN
AD566A
9.95k⍀
5k⍀
5k⍀
14k⍀
10pF
R2
5k⍀
REF
IN
19.95k⍀
DAC
OUT
0.5mA
I
O
8k⍀
I
REF
DAC
E
REF
AD509
7.5V
–V
I
=
AD561
OUT
20k⍀
2.4k⍀
REF
REF
GND
CODE
INPUT
POWER
GND
R3
26k⍀*
–V
LSB
EE
MSB
*
THE PARALLEL COMBINATION OF THE BIPOLAR OFFSET RESISTOR
AND R3 ESTABLISHES A CURRENT TO BALANCE THE MSB CURRENT.
THE EFFECT OF TEMPERATURE COEFFICIENT MISMATCH BETWEEN
THE BIPOLAR RESISTOR COMBINATION AND DAC RESISTORS IS
EXPANDED ON PREVIOUS PAGE.
Fgure 6. 10 V Voltage Output
–10–
REV. D
ADI [ ADI ]
