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TC 9400 v to f converter

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marrc

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hi!
i have implemented fig 4.2, except that have shorted digital and analog grounds, but am getting a triangular pulse at o/p whose amplitude increases with i/p vtg. pls help!
Cint: .22pf and Cref: .1 microf
 

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Cint: .22pf and Cref: .1 microf
Click to expand...
Really? Datasheet says 3CREF ≤ CINT ≤ 10CREF.

Watching which output?
Open collector output voltage may give sawtooth shape if load capacitance is too high.
 

was typo error, Cint=1microf, cref=.1 microf,
have checked both o/ps
connecting o/p directly to i/p of cro, via pullup resistor of 10k
the ic is fine as am getting proper bias voltgs of +/- 7.5 V
 

Makes no sense. Fout/2 is a square wave (possibly with slower rising edge according to Rpullup*Cload).

Something seems basically wrong with your design or oscilloscope connection.
 

by mistake i had connected a 1k resistor at the i/p. have replaced it by 1 meg but am getting a very low voltage saw tooth kind of waveform at o/p that dosent change with i/p. i dont think the ic is damaged as am still getting proper bias voltages i.e +/- 7 volts
 

someone please relply how i can chk whether the ic is still working properly or has been damaged?
 

should i change the ic? please reply i am stuck!
 

For us to assist you, we require a couple of things:

1) Your schematic. I'm not asking about the datasheet schematic, a schematic that you found on google, but your actual schematic. With actual component values.

2) Scope waveforms and/or DMM readings. Clearly labeled where those waveforms and readings were taken.

If you are unable to provide that information, then your only recourse is to start replacing components. One by one.
 
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    marrc

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schmitt trigger said:
For us to assist you, we require a couple of things:

1) Your schematic. I'm not asking about the datasheet schematic, a schematic that you found on google, but your actual schematic. With actual component values.

2) Scope waveforms and/or DMM readings. Clearly labeled where those waveforms and readings were taken.

If you are unable to provide that information, then your only recourse is to start replacing components. One by one.
Click to expand...

Hi!
i am attaching schematic diagram and o/p waveform at pin 10. the cro volt/div knob is pointing at 20mv/div and the sec/div knob is at 5ms. further the multimeter reading at pin 10 is 7v and + and - rails are +7 and -7 respectively. i am using 7.5v zeners and 15v D.C power supply.the pot is 22k
the op dosent change at all when i/p voltage is varied . please help
p.s:in spite of me trying several times an inverted w/f is getting attached, i have tried my best
 

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  • 21483d(1).pdf
    545.8 KB · Views: 82
  • 20170304_113452[1].jpg
    20170304_113452[1].jpg
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  • 20170304_113707[1].jpg
    20170304_113707[1].jpg
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FvM said:
At least the 1M resistor is wrongly connected in the schematic.
Click to expand...

the idea is to give a variable vtg input at pin 3 (while limiting the current to 10micoA)and thats what i have tried to do...will connecting the ip exactly as per fig 4.2 of data sheet solve the problem?..is the rest of the ckt. OK?..pls elaborate
 

At least the 1M resistor is wrongly connected in the schematic.

- - - Updated - - -

I don't see how the wrong IIN connection can cause the shown output, but obviously the device can't work correctly with floating IIN.
 

Pin 3 (Iin) must be DC coupled, but you have a capacitor C2 preventing that.
Is pin 7 actually tied to pin 4? There is no connecting dot.
 

schmitt trigger said:
Pin 3 (Iin) must be DC coupled, but you have a capacitor C2 preventing that.
Is pin 7 actually tied to pin 4? There is no connecting dot.
Click to expand...

have attached corrected schematic..is it OK now? but still i am getting the same o/p. the preset at pin no 3 is added to vary i/p voltage and is also there in fig 4.2 of datasheet(R3).
a quick reply would be appreciated
 

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  • 20170304_113707[1].jpg
    20170304_113707[1].jpg
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  • 21483d(1).pdf
    545.8 KB · Views: 78

20170315_173205[1].jpg

HQ image attached. Vss and Vref are shorted right?
 

Hi,

instead of posting fotos of your monitor you just could use the "screenshot".

If you upload this file as PNG then the file size (in bytes) is less than yours while having best quality.


Klaus
 

Hi !
You havent replied..
Since when i posted last i have found that was incorrectly connecting the cro strobe pins(was not connecting the ground of the cro to the gnd of the ckt)
i think thats why i was getting the w/f like the ones i have attached..
now i have rectified that mistake but am getting following o/p:
when i/p vtg is varied o/p amplitude varies but frequency remains same....
am getting a sawtooth waveform at the op whose frequency dosent change with i/p
pls help!
 

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