0 reference inputs, Applications information – Rainbow Electronics ADC10D020 User Manual

Page 24

Applications Information

(Continued)

2.0 REFERENCE INPUTS

The V

and V

pins should each be bypassed with a 5 µF

(or larger) tantalum or electrolytic capacitor and a 0.1 µF
ceramic capacitor. Use these pins only for bypassing. DO
NOT connect anything else to these pins.

Figure 4 shows a simple reference biasing scheme with
minimal components. While this circuit will suffice for many
applications, the value of the reference voltage will depend
upon the supply voltage.

The circuit of

Figure 5 is an improvement over the circuit of

Figure 4 because the reference voltage is independent of
supply voltage. This reduces problems of reference voltage
variability. The reference voltage at the V

REF

pin should be

bypassed to AGND with a 5 µF (or larger) tantalum or
electrolytic capacitor and a 0.1 µF ceramic capacitor.

The circuit of

Figure 6 may be used if it is desired to obtain

a precise reference voltage not available with a fixed refer-
ence source. The 240

Ω

and 1k resistors can be replaced

with a potentiometer, if desired.

20025569

FIGURE 2. The ADC10D020 is designed for use with
differential signals of 1.0 V

P-P

with a common mode

voltage of 1.5V. The signal swing should not cause any

pin to experience a swing more than 300 mV beyond

the supply rails.

20025570

FIGURE 3. Use of an input transformer for

single-ended to differential conversion can simplify

circuit design for single-ended signals.

ADC10D020