IF Counter Structure

The LC72136 IF counter is a 20-bit binary counter. The result of the count can be read out serially, MSB first, from the

DO pin.

IF frequency (Fc) measurement consists of determining how many pulses enter the IF counter in a specified

measurement time (GT).

Fc =

(C = Fc

× GT)

C: count value (number of pulses)

Sample IF Counter Frequency Calculations

1. For a measurement time (GT) of 32 ms and a count value (C) of 53980 (hexadecimal), which is 342,400 (decimal)

IF frequency (Fc) = 342,400 ÷ 32 ms = 10.7 MHz

2. For a measurement time (GT) of 8 ms and a count value (C) of E10 (hexadecimal), which is 3600 (decimal)

IF frequency (Fc) = 3600 ÷ 8 ms = 450 kHz

C

GT

No. 5038-16/23

LC72136, 72136M

GT1

GT0

Measurement time

Measurement period (GT) (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