lc72137 Sanyo Semiconductor Corporation, lc72137 Datasheet - Page 15

• Manufacturer Part Number: lc72137
• Description: Pll Frequency Synthesizer For Electronic Tuning
• Manufacturer: Sanyo Semiconductor Corporation

IF Counter Structure
The LC72137 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.
The IF frequency (Fc) is measured by determining how many pulses were input to the IF counter in the stipulated
measurement time, GT.
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)
2. For a measurement time (GT) of 8 ms and a count value (C) of E10 (hexadecimal), which is 3600 (decimal)
GT1
0
0
1
1
Fc =
IF frequency (Fc) = 342,400 ÷ 32 ms = 10.7 MHz
IF frequency (Fc) = 3600 ÷ 8 ms = 450 kHz
GT
GT0
C
0
1
0
1
Measurement period (GT) (ms)
(C = Fc GT)
16
32
4
8
Measurement time
Wait time (t
C: count value (number of pulses)
LC72137, 72137M
3 to 4
3 to 4
3 to 4
3 to 4
WU
) (ms)
No. 5743-15/22