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INA240: INA240A2

September 2, 2019, 1:01 am
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Part Number: INA240

Hello,

we need to track the resonance frequency of a DUT by measuring the phase shift between voltage and current of the DUT.

The DUT is driven by sinusoidal voltage between 15Vpp and 45Vpp. The DUT has a minimal Impedance between 70Ω and 200Ω.

We are using the INA240-A2 for this purpose, but we measure a delayed output of the INA240 in comparison with a oscilloscope current probe in the area of 0.8µs to 1.2µs.

Because the signal frequency is in the area between 90kHz and 120kHz this delay represents a additional phase shift.

So we have following questions:

- can this delay be removed?

- is the output delay constant?

- is there an error in our circuit?

- is the INA240 the wrong selection for this task?

 

Orange = Voltage

Green = current (Oscilloscope probe)

Blue = INA240-A2 output voltage

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OPA350: Input offset voltage calculation using Tina -TI ; OPA 350

September 2, 2019, 8:31 pm
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Part Number: OPA350

Hi,

I am referring to the TI precision Labs, course by TI (link), and while simulating input offset voltage, I am unable to get right offset voltage. 

According to the instructor, input offset voltage should be  -150uV. Pic (Fig. 1).

The answer I am getting is -444.53fV (Fig. 2).

Analysis --> DC Analysis --> Calculate nodal voltages in Tina-TI.

I am not able to make out the error, 

                                                                    Fig. 1

                                                                                                 Fig. 2

Regards,

Tapas

                                                      

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THS4551: TOP MARKING

September 2, 2019, 11:33 pm
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Part Number: THS4551

We purchased 136pcs * THS4551IRUNR from the distributor  the part marking is "XJ51". But according to the data sheet the marking should be "4551", pls help to confirm if XJ51 is right.

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INA332: What is the maximuim capacitance which can be connected to INA332 output?

September 2, 2019, 11:54 pm
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Part Number: INA332

 Hello guys,

 One of my customers wants to drive some capacitances by INA332 output.

 Could you please tell me what the maximuim capacitance which can be connected to INA332 output is?

 According to the graph, PERCENT OVERSHOOT vs LOAD CAPACITANCE on page 7 in INA332 datasheet,

 http://www.ti.com/jp/lit/ds/symlink/ina332.pdf

  10000pF is plotted as the maximum. But the customer wanted to drive 0.5uF.

 Is there any problem (Ex. device broken, device damage, output oscillation) on INA332, if 0.5uF is connected to the output?

 Your reply would bemuch appreciated.

 Best regards,

 Kazuya.

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THS7372: VGA rise/fall time test fail

September 3, 2019, 2:00 am
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Part Number: THS7372

Hi Team,

Now we get VGA rise/fall time test fail (>spec time)as attached test report.

We concern about the down resistor, series resistors and pi filter on the VGA trace.

Please kindly double check the schematic, and advice how to improve the rise/fall time.

Thanks

(Please visit the site to view this file)

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LM2904: LM2904PWR PCN issue and Screen printing issue

September 3, 2019, 2:45 am
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Part Number: LM2904

we have buy LM2904PWR  and find the Screen printing is different, show as attached picture.

show as the red square, the screen printing is different.

even though their are from different factory.

and their X-ray picture are also different.

so we need TI to confirm if they are both TI LM2904PWR? or one of them is not  TI parts? 

if they are the same to LM2904PWR, how to explain the different.

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OPA2180: Rogowski coil signal acquisition

September 3, 2019, 6:11 am
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Part Number: OPA2180

1、I use a signal generator to generate 50MV, 50HZ signal to the J2 input terminal of TIDA-00777.When I connect the positive signal to the PIN of J2 and the negative terminal to PIN2, the output signal is the correct amplification factor, but when I reverse the connection, the output signal is wrong, the signal is very small.Assume that the magnification is about 70 times。The first picture is the output waveform of the positive connection, and the second picture is the output waveform of the reverse connection. Why?

2、How large is the normal operating current of the OPA2188? I now use the TPS65131 which output ±15V to power 7channel OPA2188s, and I feel that the output current is not enough.

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LMH5401-SP: Cold Sparing?

September 3, 2019, 9:05 am
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Part Number: LMH5401-SP

Is the LMH5401-SP cold sparing? We plan to use this part as a DE-DE amplifier w/unity gain. We will have active signal transitions on this device when the power is removed from the part. Note that the input signals are also AC coupled. 

This is most likely an exercise in calculating the residual RMS voltages that will pass through the AC coupling capacitors and then be divided down by the feedback circuits. 

It would be good to know if this device is cold sparing or at least tolerant of active inputs when unbiased.

Thanks

John

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LMH6702: a way to drive a speed pulse (PECL) into a 3-5V 50 ohm load

September 3, 2019, 11:33 am
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Part Number: LMH6702

Team, 

Looking to see if I can use the LMH6702 to drive a speed pulse (PECL) into a 3-5V 50 ohm load.

I’m not sure I’m in the digital, analog or uwave region.

In the analog domain, the slew rate would be 10,000V/us, BW in 1GHz. 

In the digital domain it’s a rise time of 500ps.

Both working into a 50 Ohm load. 

Would the LMH6702 be able to do this?

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OPA820: Design Methodology for MFB Filters

September 3, 2019, 12:26 pm
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Part Number: OPA820

Hello, I'm using the document "www.ti.com/lit/an/sboa114/sboa114.pdf" "Design Methodology for MFB Filters in ADC Interface" to design a 2nd order Low-pass filter with a gain of 1 and Fc = 15KHz. I'm looking at the example on page 8 and have a question about the calculation of R2. The document says that R2 is calculated by Equation 9 on page 4. I don't know what the term 2kT is and would like ask someone for help.

The in and en are from the datasheet of the OPA820, am I correct?

If anyone can help me I would be very thankful.

Respectfully,

Joe

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INA303: Draws huge current

September 3, 2019, 12:27 pm
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Part Number: INA303

As mentioned in my earlier query, I am using INA303A2 to sense overcurrent condition set at 170mA. To test this circuit I set the load current from Power supply at 180mA and gradually increase the voltage. But the supply's short LED turns on as soon as the voltage knob is moved. This even happens even if the INA303 circuit is not powered on and only the load is powered. Any idea what could be the issue?

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TAS2562H - 4

September 3, 2019, 6:15 pm
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INA199: INA199 going to positive saturation while connecting to -ve bus supply

September 3, 2019, 10:31 pm
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Part Number: INA199

Hello,

I am using INA199A1DCKR in one of my DC energy metering project for telecom applications.

DC voltage to be measured - 60VDC max using LM358 in differential mode

DC current to be measured - 100A max using 100A/50mV shunt from INA199

The 60VDC input to the system is fed to an isolated SMPS generating 5VDC for my control supply (for INA199 with ref pin connected to controller supply ground as well)

Same 60VDC is being monitored in differential mode

Current is being sensed in low side topology.

Since, the project is for telecom application; i am getting 48VDC GND as distribution terminal which is input to my DCEM shunt terminal; the other end of shunt is then fed to the load and positive terminal is directly connected to the load.

The issue is, as soon as i connect 48VDC GND (Isolated from 5VDC and GND which is supply to INA199) to shunt terminals (at this point load is not switched ON); INA199 is going to positive saturation and giving maximum output.

At this point, I am seeing -0.5VDC at both IN+ and IN- pin of INA199. I know its common mode range on lower side is -0.3V. May be this is causing INA199 to latch-up but it is not damaging.

I want to know what I can do to avoid this issue

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TL081: Input Impedance

September 4, 2019, 12:57 am
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Part Number: TL081

Hi Team, we have a customer that would like to ask the input capacitance value of TL081CP. He also wants to confirm if he could leave the offset pin floating.

We hope you could help us. 

Thank you.

-Mark

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OPA171-Q1: Could you please help to understand the circuit

September 4, 2019, 1:10 am
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Part Number: OPA171-Q1

Hello All,

I have given a circuit as below and simulated in P-Spice. I am confused of the circuit working behavior.

1. Could anyone help to understand the circuit behavior and the impact of 5V at R5 and R6 node.

2. also explain solved solutions for the voltages displayed in simulation result. 

Thanks in advance.

Sathish Kaliappan

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TL082: Non linearity closed at 0V input

September 4, 2019, 1:35 am
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Part Number: TL082

Hi team,

I've simulated following schematic, and found 1.55V non linearity voltage at closed at 0V input. About 1.55V is reasonable value?

Best regards,

Takeshi Sasaki

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TLV7031: voltage at in+ and in- without supply voltage

September 4, 2019, 2:14 am
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Part Number: TLV7031

Hi,

is it allowed if the supply voltage of the TLV7031 (3.3V) is turned off and there is still a voltage at the in+ and in- inputs (e.g. 5V)?

it's no problem for me if the output is not defined but the the TLV should not be damaged

thanks

chris

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LM2903-Q1: Difference between part numbers

September 4, 2019, 6:54 am
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Part Number: LM2903-Q1

Hello All,

To select correct part number for automotive products, can you please specify the difference between following part numbers:

LM2903AVQPWRG4Q1 and LM2903AVQPWRQ1

Regards

Shrikant L

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VCA820: Non-linear issue of VCA820

September 4, 2019, 7:59 am
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Part Number: VCA820

Hi team,

   I want to use this device as below,  Rf=845Ohm, Rg=16.9, Vg=2V, which means Avmax=40dB;

   When I apply VG1 signal, Vpp=5mV, f=20MHz, we can see that Vpp of VF1 is about 700mV. This is not aligned with the gain*Vpp=500mV. What is the reason? 

   Also, I am not clear about the relationship between Vg and gain, it is not clear in our datasheet. Please help answer these two questions ASAP. I have attached the TINA file to help you simulate this device. Thanks. 

(Please visit the site to view this file)

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OPA2364: Difference/s between OPA2364IDGKT & OPA2364AIDGKT

September 4, 2019, 8:06 am
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Hello!

Can you please advise the difference between these two?
We checked the datasheet and found no difference.


Thank you for your help.

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