AnsweredAssumed Answered

74LVC163 as VHF prescaler

Question asked by József Hermann on Jan 4, 2017

Dear Communty Members,

I would like to build a /16 frequency divider for the also NXP TDA7021T FM receiver chip (100MHz range) using LVC163 or LV393 counters (to display the reception frequency=fosc-0,075MHz, note the TDA has low IF=75KHz).

The supply voltage in 2-3V range (not stable, two AA battery).


Previosly, I successfully used the 74LV163 but on fixed 3,3V supply voltage and an pre-amplifier shaping sinusoid oscillator signal to near square-wave.


I would like to elimanate the pre-amplifier, only using a single BFS17 transistor in common collector configuration.

The LVC163/LV393 input would be biased to VCC/2 by two resistors (CMOS input has half supply threshold) and using capacitive coupling between the transistor buffer and the CLK_In. Note, the TDA oscillator signal has 250mVrms level.

Theoritically, the internal inverter at the CLK pin should amplifiy and shape the signal enough for other internal circutry (Flip-Flops, setup logic). 


I would like to ask whether sombody has similar experiment with LVC163, especially power consumption and it really could handle such low level AC coupled signals detailed above?


Thank you for your comments in advance!


Kind regards,