OPA170-Q1: discrete solution to replace LM1815

Hi Kevin,

but both chips are totally different. The OPA170 does not contain a monoflop. e.g.

Why is the costumer interested in a discrete solution?

Kai

Hi Kevin,

The OPA170 might be able to work as the amplifier portions of the product you referenced, but there is much more going on in the circuit. Let us know what specific functionality with amplifiers the customer is requiring and we can provide some more direct advice.

Best,
Paul

Hi kai,

This is because LM1815 do not have automotive qualified version. so we want to try to use automotive qualified device to build a discrete solution.

Kevin

Hi Paul,

the input siganl is a sinusoidal wave, the minimum input amplitude is +/-233mV, the maximum input amplitude is +/- 180V, frequency is below 1kHz. Customer need a solution to process the input signal, to get a PWM signal that have the same frequency as the input siganl. then, the PWM signal is connent to a MCU TIM input (timer) and MCU calculate the frequency.

would you please help to suggest a solution? Thanks.

Kevin

We have a circuit cookbook that covers a PWM generator - it doesn't quite meet your needs, but is this the type of waveform the customer is looking for? www.ti.com/.../sboa212.pdf

Otherwise, it sounds like the customer is really looking for a type of zero-crossing detector. The most difficult requirement is the wide input voltage range, but I think with the creative use of input diodes, you could limit the input voltage and create the waveform you're looking for. I think a comparator would be best for this application though.

Let me know what type of PWM output your customer is looking for.

-Paul

Hi Paul,

we think it should be working as a zero-crossing detector. would you please share your idea about how to use input diode to handle the wide input voltage range? we think it should like have buffer amplifier to handle this wide input voltage range and then, the amplifier output go to comparator, right?

Kevin

Hi Kevin,

the range of input signal is huge, as if the signal is coming from an inductive sensor. Is this right?

Kai

Hi Kai,

Yes, Variable reluctance (VR) sensors, also known as mag (magnetic) sensors are
built with a wire wound around a permanent magnet (pole) similar to a solenoid or DC
motor.

Kevin

Hi Kevin,

can you give us a datasheet of this sensor?

Kai

Hi Kai,

customer didn't get sensor datasheet from their end customer, they only got sensor output signal description: the input siganl is a sinusoidal wave, the minimum input amplitude is +/-233mV, the maximum input amplitude is +/- 180V, frequency is below 1kHz.

Kevin