LC72121MA
Structure of the IF Counter
The LC72121MA IF counter is a 20-bit binary counter, and takes the IF signal from the IFIN pin as its input. The result
of the count can be read out serially, MSB first, from the DO pin.
IF counter
(20-bits binary counter)
IFIN
(Fc)
L
M
S
S
B
B
DO pin
4/8/32/64
ms
(GT)
0 to 3 4 to 7 8 to 11 12 to 15 16 to 19 (C)
CTE
GT0 GT1
C = Fc × GT
Measurement time
GT1
GT0
Measurement time (GT)
Wait time (tWU)
0
0
4 ms
3 to 4 ms
0
1
8
3 to 4
1
0
32
7 to 8
1
1
64
7 to 8
The IF frequency (Fc) is measured by determining how many pulses were input to the IF counter in the stipulated
measurement time, GT.
C
Fc = GT
(C=Fc × GT)
C: Counted value (the number of pulses)
IF Counter Frequency Measurement Examples
(1) When the measurement time (GT) is 32ms and the counted value (C) is 53980 (hexadecimal) or 342,400
(decimal).
IF frequency (Fc) = 342400 ÷ 32ms = 10.7MHz
5
3
9
8
0
01010011100110000000
(2) When the measurement time (GT) is 8ms and the counted value (C) is E10 (hexadecimal) or 3600 (decimal).
IF frequency (FC) = 3600 ÷ 8ms = 450kHz
0
0
E
1
0
00000000111000010000
No.A2009-16/24