OPTIONAL CONVERSION TIME ADJUSTMENT
The ADC76 may be operated with faster conversion times
for resolutions less than 14 bits by connecting the Short
Cycle (pin 32) as shown in Table III. Typical conversion
times for the resolution and connections are indicated.
+15VDC
(a)
27
1.8MΩ
Ω
Ω
10k to 100k
Offset Adjust
R
1
Comparator In
–15VDC
+15VDC
Resolution (Bits)
Connect Pin 32 to
16
15
Pin 16 Pin 15 Pin 14 Pin 13
16µs 15µs 13µs 12µs
14
13
12
Open
(b)
27
R
Typical Conversion Time 17µs
1
180kΩ
180kΩ
Ω
Ω
10k to 100k
TABLE III. Short Cycle Connections for 12- to 16-Bit
Resolutions.
Offset Adjust
Comparator In
22kΩ
–15VDC
Clock Rate Control may be connected to an external multi-
turn trim potentiometer with a TCR of ±10ppm/°C or less as
shown in Figure 12. The typical conversion time versus the
Clock Rate Control voltage is shown in Figure 13. The effect
of varying the conversion time and the resolution on Linear-
ity Error and Differential Linearity Error is shown in Figure
6.
FIGURE 10. Two Methods of Connecting Optional Offset
Adjust.
+15VDC
Gain Adjust
270kΩ
29
10kΩ to 100k Ω
+15VDC
Gain Adjust
23
0.01µF
Internal Clock
5kΩ
Frequency Adjust
Clock Rate Control
–15VDC
22
Analog Common
FIGURE 12. Clock Rate Control, Optional Fine Adjust.
FIGURE 11. Connecting Optional Gain Adjust.
20
Adjust the Offset potentiometer until the actual end point
transition voltage occurs at EIN Off. The ideal transition
voltage values of the input are given in Table I.
Typical
Gain—Connect the Gain adjust potentiometer as shown in
Figure 11. Sweep the input through the end point transition
voltage; that should cause an output transition to all bits on
EIN On. Adjust the Gain potentiometer until the actual end
point transition voltage occurs at EIN On.
14-Bit Operation
15
16-Bit Operation
Table I details the transition voltage levels required.
10
0
2
4
6
8
CONVERT COMMAND CONSIDERATIONS
Control Voltage on Pin 23 (V)
Convert command resets the converter whenever taken high.
This insures a valid conversion on the first conversion after
power-up.
FIGURE 13. Conversion Time vs Clock Rate Control
Voltage.
Convert command must stay low during a conversion unless
it is desired to reset the converter during a conversion.
®
ADC76
8
BB [ BURR-BROWN CORPORATION ]
