TLV9302: replacing TL082 issue

Howard Zou

Genius 12365 points

Part Number: TLV9302
Other Parts Discussed in Thread: TL082, TLV9102, TLV9352, , TLV9152

Hi,

my customer was using TL082 to sense the output current of an PSFB converter.

TL082 is used to sense the current with a shunt resistor placing at ground side(R27).

TL082 is powered by ±5V. The switching frequency of the PSFB is around 120k.

A 5mohm resistor is placed between Isamp1- and AGND.

The customer would like to test some OPA with lower drift to replace TL082.

So we recommended TLV9102, TLV9302, TLV9152, TLV9352.

With TL082, with the same current, the output of TL082 is constant with VOUT increasing.

With TLV9102/9302/9152/9352, and we keep the current constant, the output of the amp will increase along with VOUT increasing, which is not acceptable.

We don’t know what parameter difference between TLV series and TL082 could lead to such new problem.

Since it's placed at low side, so common mode voltage is almost zero and should not be the cause.

over 3 years ago

0 Jerry Madalvanos over 3 years ago

TI__Mastermind 22361 points

Hello Howard,

Could you clarify what you mean by constant output with VOUT increasing? There is no VOUT in your schematic and your resistor on the output (R69) does not show its connection/appears floating. Do you possibly have oscilloscope shots of the behavior you're seeing?

Best,
Jerry

0 kai klaas69 over 3 years ago in reply to Jerry Madalvanos

Guru 140200 points

Hi Jerry,

a "VOUT" can be seen in the first picture :-)

Kai

0 Howard Zou over 3 years ago in reply to Jerry Madalvanos

TI__Genius 12365 points

Vout means the DCDC's output voltage. We are just measuring the output current of the DCDC stage with TL082.

0 Jerry Madalvanos over 3 years ago in reply to Howard Zou

TI__Mastermind 22361 points

Howard,

Are you able to provide any more information about the circuit? If VOUT is decoupled from the shunt resistor, the only thing driving IDC1 should be the current sense circuit. Can you provide a more complete circuit, or a simulation file of the circuit in either TINA or PSpice for TI?

There is an architecture difference between TL082 and TLV9302. TL082 is JFET whereas TLV family is CMOS.

Best,
Jerry

0 Michael Steffes over 3 years ago

Guru 47485 points

Your problem statement is mystifying,

I do also wonder why you use a +/-15V device on +/-5V application,

might look at the TLV9102 which was in your original list, normally, the closer you match your supply needs to the device range, the lower the quiescent current will be.

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TLV9302: replacing TL082 issue