TLV6001-Q1: Current sensing OPAMP

CHO SR

Genius 3415 points

Part Number: TLV6001-Q1
Other Parts Discussed in Thread: TLV9001-Q1, OPA2991-Q1, INA139-Q1

Tool/software:

Hi,

The customer tried to place the shunt resistor in position 1 and sense the current.

However, VBAT is being entered at all times, causing dark current problems.

So, we are planning to place it in position 2 and sense the current.

Position 2 changes the voltage at both ends of the shunt resistor by +/- when the CW/CCW is operated.

Please recommend a product that can sense both.

Current Spec : Peak: 5A~30A, NOM : 15A

If there is no product to recommend in position 2, can I use TLV9001-Q1 in position 1?

5 months ago

0 Clemens Ladisch 5 months ago

Guru 280390 points

There are circuits that allow to measure both positive and negative currents. Please show your measurement circuit, and the values of VBAT and of the opamp's supply.

0 Jerry Madalvanos 5 months ago in reply to Clemens Ladisch

TI__Mastermind 28526 points

Hello Cho,

The device you can use also is based upon what value of shunt resistor you plan on using. In the below example circuit, bidirectional current sense is achieved by biasing up the input voltage above V- and allowing the input voltage to swing in either direction without running into the common-mode or output limits of the op amp. Something similar can be done here.

https://www.ti.com/lit/an/sboa223b/sboa223b.pdf

Best,
Jerry

0 CHO SR 5 months ago in reply to Jerry Madalvanos

Genius 3415 points

Thank you for your support.

supply 0~ 36V

I =5A ~ 30A

Shunt resistor will be used 2 mΩ.

Please recommend Q100 certified high side current sensing products.

+1 Jerry Madalvanos 5 months ago in reply to CHO SR

TI__Mastermind 28526 points

Hello Cho,

If op amp supply is 36V, I would recommend OPA2991-Q1. This could be used in similar way to the example circuit posted above. Please let me know if you have questions on how to implement this.

Please note that July 4th is US holiday, and responses may be delayed.

Best,
Jerry

+1 Clemens Ladisch 5 months ago in reply to CHO SR

Guru 280390 points

So the measured voltages are between 10 mV and 60 mV. The amplifier's input offset error should be much smaller than this; the OPA2291-Q1 would be fine.

But a difference amplifier circuit is sensitive to resistor tolerances; if you care about accuracy, it might make sense to use a current-sense amplifier with integrated, matched resistors like the INA139-Q1.

0 CHO SR 4 months ago in reply to Jerry Madalvanos

Genius 3415 points

Hi Jerry,

The Vbus is 9 to 16 V.

SYSTEM LOAD has become a DC motor, so it will be used until MAX 30A.

Please guide me on how to configure the elements of R1, R2, R3, R4, and Rshunt.

0 Jerry Madalvanos 4 months ago in reply to CHO SR

TI__Mastermind 28526 points

Hey Cho,

If your shunt resistor is already selected at 2mOhm, what is the max voltage range of your MCU ADC?

Best,
Jerry

0 CHO SR 4 months ago in reply to Jerry Madalvanos

Genius 3415 points

Hi Jerry,

It is said that the ADC input of the MCU is possible up to 5V.

Is there anything else I need to check?

+1 Jerry Madalvanos 4 months ago in reply to CHO SR

TI__Mastermind 28526 points

Hey Cho,

If the shunt resistor is 2mOhm, your maximum input voltage is +/-60mV. If you set your output common mode to 2.5V and you want to maximize the linear range of the op amp, you will swing from 0.1V to 4.9V on the output. To scale 60mV to this voltage your gain needs to be 40V/V, and you will need a 2.5V reference buffered from a second op amp.

Best,
Jerry

0 CHO SR 4 months ago in reply to Jerry Madalvanos

Genius 3415 points

Hi Jerry

1. The current source flowing through 30A becomes a battery and is placed as shown in the figure below.

Even if the voltage changes from 9 to 16V, can the current be detected?

2. With the circuit configured below, it seems that the current flowing in R1 (shunt resistor) can be detected from -30A to 30A.

Is it possible to detect a two-way current flowing through the shunt resistor?

0 Jerry Madalvanos 4 months ago in reply to CHO SR

TI__Mastermind 28526 points

Hello Cho,

Yes, the voltage on the input of the amplifier is just the differential voltage across R1.

I'm not sure I understand the second question. If the current sensed can be from -30A to 30A, isn't -30A to 30A a two-way current through the shunt resistor?

Best,
Jerry

0 CHO SR 4 months ago in reply to Jerry Madalvanos

Genius 3415 points

Thank you.

Yes, -30A to 30A are bi-directional currents through the shunt resistor.

I understand the operation of the schematic as below.

Is it correct?

When current flows to CCW (0A to +30A), VF1 outputs from 2.5V to 5V.

When current flows to the CW (-30A to 0A), VF1 outputs from 0V to 2.5V.

+1 Jerry Madalvanos 4 months ago in reply to CHO SR

TI__Mastermind 28526 points

Hello Cho,

That is correct.

Best,
Jerry

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TLV6001-Q1: Current sensing OPAMP