5

®

VFC110

NONLINEARITY vs FULL SCALE FREQUENCY

10

Full Scale Frequency (Hz)

1

0.1

0.01

0.001

4

10

5

10

6

10

7

NONLINEARITY vs INPUT VOLTAGE

0

Input Voltage (V)

0.02

0.01

0

–0.01

–0.02

123456789

10

1

0.8

0.6

0.4

0.2

0

–0.2

–0.4

–0.6

–0.8

–1

f

f

OPERATION

Figure 1 shows the connections required for operation at a

full-scale output frequency of 4MHz. Only power supply

required for this mode of operation. A 0V to 10V input

voltage produces a 0Hz to 4MHz output frequency. The

internal input resistor, one-shot and integrator capacitors set

the full-scale output frequency. The input is applied to the

summing junction of the integrator amplifier through the

25k

Ω internal input resistor. Pin 14 (the non-inverting ampli-

fier input) should be referred directly to the negative side of

limited to approximately –1V to +1V referred to analog

ground. This allows the non-inverting input to Kelvin-sense

the common connection of V

FIGURE 1. 4MHz Full-Scale Operation.

ground-drop errors. The input impedance loading V

equal to the input resistor—approximately 25k

Ω.

OPERATION AT LOWER FREQUENCIES

The VFC110 can be operated at lower frequencies simply by

limiting the input voltage to less than the nominal 10V full-

scale input. To maintain a 10V FS input and highest accu-

racy, however, external components are required (see Table

I). Small adjustments may be required in the nominal values

indicated. Integrator and one-shot capacitors are added in

parallel to internal capacitors. Figure 2 shows the connec-

tions required for 100kHz full scale output. The one-shot

one-shot connection (pin 6) is not short-circuit protected.

Short-circuits to ground may damage the device.

2

14

IN

V

112

11

One-Shot

V

REF

–V

S

Analog Ground

413

NC

3

6

8

Logic Ground

OUT

f

10

+V

S

7

NC

5

NC

50pF*

NC

PU

R

680

Ω

–15V

+15V

V

L

+5V

0 to 4MHz

25k

Ω*

0 to

+10V

* Nominal Values (±20%)