IF Counter Structure

The LC72131 IF counter is a 20-bit binary counter. The result, i.e., the counter’s msb, can be read serially from the DO pin.

The IF frequency (Fc) is measured by determining how many pulses were input to an IF counter in a specified

measurement period, GT.

Fc =

(C = Fc

× GT)

C: Count value (number of pulses)

1. IF Counter Frequency Calculation Examples

• When the measurement period (GT) is 32 ms, the count (C) is 53980 hexadecimal (342400 decimal):

IF frequency (Fc) = 342400

÷ 32 ms = 10.7 MHz

• When the measurement period (GT) is 8 ms, the count (C) is E10 hexadecimal (3600 decimal):

IF frequency (Fc) = 3600

÷ 8 ms = 450 kHz

C

GT

No. 4921-16/23

LC72131, 72131M

GT1

GT0

Measurement time

Measurement period (GT) (ms)

Wait time (twu) (ms)

0

0

4

3 to 4

0

1

8

3 to 4

1

0

32

7 to 8

1

1

64

7 to 8