TC9400CPD View Datasheet(PDF) - Microchip Technology

Part Name

Description

MFG CO.

TC9400CPD

Voltage-to-Frequency/Frequency-to-Voltage Converters

Microchip Technology 

TC9400/9401/9402

FIGURE 7-4:

DC - 10kHz CONVERTER

+5V

14

VDD

TC9400A

42

TC9401A

See

Figure 7-1:

TC9402A

Threshold

FIN

"Frequency

Input Level

Detect 11

Shifter"

3µsec

Delay

Threshold

Detector

Offset

Adjust

+5V

2kΩ

-5V

100kΩ 2 Zero Adjust

2.2kΩ

IBIAS

VSS

1

4

10kΩ

VREF

7

–

Op

Amp

+

VREF

(Typically -5V)

V+

*

FOUT/2 10

Output

V+

Common 9 *

*

FOUT 8

*Optional/If

Buffer is Needed

VREF

OUT

5

12pF

IIN 3

60pF Amp

Out 12

CREF

56pF

RINT

1MΩ

CINT

1000pF

VOUT

GND

6

7.4 Output Filtering

The output of the TC9400 has a sawtooth ripple super-

imposed on a DC level. The ripple will be rejected if the

TC9400 output is converted to a digital value by an inte-

grating analog-to-digital converter, such as the TC7107

or TC7109. The ripple can also be reduced by increas-

ing the value of the integrating capacitor, although this

will reduce the response time of the F/V converter.

The sawtooth ripple on the output of an F/V can be

eliminated without affecting the F/V's response time by

using the circuit in Figure 7-5. The circuit is a capaci-

tance multiplier, where the output coupling capacitor is

multiplied by the AC gain of the Op Amp. A moderately

fast Op Amp, such as the TL071, should be used.

FIGURE 7-5:

RIPPLE FILTER

VREF OUT 5

TC9400 IIN 3

AMP OUT 12

47pF

1M .001µF

200

GND

6

.01µF 1M

0.1µF

2–

3+

1M

+5

7

6

4

-5

VOUT

TL071

DS21483B-page 14

© 2002 Microchip Technology Inc.

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