LM2907-N: Frequency to Voltage Converter Circuit

Hi Neha,

you could do it this way. For 62.5Hz:

...and 125Hz:

neha_lm2907.zip

Also, swap R1292 and C77 and wire R1292 as pull-down.

Kai

Or like this, with your 100k + 2u2 post filter :

Kai

Or with this faster compromise filter:

Kai

Hi Neha,

Thanks Kai for the series of the simulation!

I think that the following inquiry is related to this one as well. Please let us know if you have additional questions.  

https://e2e.ti.com/support/amplifiers-group/amplifiers-internal/f/amplifiers-internal-forum/1211020/lm2907-n-f-to-v-converter/4570244#4570244

Best,

Raymond

Thank you Kai for the quick simulation.

We have tried your circuit but not getting results as per your simulation. However we tried multiple combinations of R1 and C1 as below but getting output Voltage in the range of 7.7 - 10 V for given frequency range.We are not getting lower voltage as shown in simulations. 

We are using 14Pin LM2907 IC but we have replicated the same circuit.

Any logic to increase frequency band because for certain combinations we are getting desired frequency but not the full band.Also for many combinations,Vout is not as per formula specified in datasheet.

Kindly share LTSpice model of your simulated circuit or IC if possible.

Thanks in advance

Hi Neha,

keep in mind that the 8 pin version and 14 pin version of LM2907 are differemt. So, please show a complete schematic of your 14 pin version.

Kai

Hi Kai,

We have used below 8Pin Ckt with 14 Pin IC with below modification:

1. Pin 3 and Pin 4 short

2. Pin 5 as EMIT and Pin 10 as IN-

3. Pin 11 and Pin 12 short

Hi Neha, 

I replied to the inquiry in the thread below. 

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1213147/lm2907-n-lm2907-n-8pin-and-14-pin

There are differences between LM2907 and LM2917, you need confirm which one you are selecting. 

In addition, you need to tell us the frequency input DC and PWM amplitude between 65Hz -110Hz. Two parts has two different trigger mechanism, so the input parts are not interchangeable. Also, please provide us the supply voltage and output level of the design requirements. 

Best,

Raymond 

Hi Neha,

Neha Sawade said:

Kindly share LTSpice model of your simulated circuit or IC if possible

Here it comes:

lm2907_8.lib

Kai

Hi Neha,

you should not only read the datasheet of LM2907-N but also this appnote:

AN-162 LM2907 Tachometer/Speed Switch Building Block Applications

And this thread discusses how to implement the ".lib" file into LTSpice:

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1034332/pga281-ltspice-simulation-error

Kai

HI Raymond,

We are using LM2907 14 Pin IC. Our Working Voltage is 12V and Frequency is 65Hz -110Hz. 

We have used below 8 pin circuit with our 14PIn IC with below modifications:

1. Pin 3 and Pin 4 short

2. Pin 5 as EMIT and Pin 10 as IN-

3. Pin 11 and Pin 12 short

Hi Neha, 

The differences between LM2907N-8 and LM2907N-14 are the following shown in red marks. 

The input pin1 of LM2907-8 is compared to GND, while input pin1 in LM2907N-14 is user defined. If you use LM2907N-14, you need to configure the comparator properly. So is pin7 of LM2907N-8 and Pin10 in LM2907N-14 package. I do not think that we have a model for LM2907-14 pin package, so I used LM2917-14 to simulate the functionality. 

LM2907-14 04062023.TSC

Below is the block diagram. Please let me know if you need additional help. 

Best,

Raymond