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LM358: LM358N (ST) Replace by LM358AP (TI)

February 25, 2019, 11:16 pm
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Part Number:LM358

Hi Team,

one of my customer  using LM358AP (Dual Opamp) in their Fire alarm System .

 

Earlier they are using ST LM358N that we replaced by LM358AP .Now out of both  OPamp (LM358AP) second Opamp do not operate.

 

Please check  below observation tables of both devices.

 

LM358AP (TI)

LM3358N(ST)

Pins

V at Non operating

V at Operating condition

Pins

V at Non operating

V at Operating condition

IN1-

21.8

17

IN1-

21.8

18

IN1+

20.4

20.1

IN1+

20.3

20.1

OUT1

 

Working

OUT1

 

Working

IN2-

22.5

22.5

IN2-

22.5

22.5

IN2+

21.9

22.5

IN2+

21.8

22.5

OUT2

 

Not working

OUT2

 

Working

 

Please advise how we can resolve .

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AMC1200: AMC1200B input bias current range

February 25, 2019, 11:48 pm
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Part Number:AMC1200

Hi

Can you please give the input bias current & input offset current specifications of AMC1200B? I can't find them in the datasheet.

Thanks & Regards,

Naveen.

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TINA/Spice/THS4531A: Stability analysis with spice model

February 26, 2019, 12:17 am
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Part Number:THS4531A

Tool/software:TINA-TI or Spice Models

Hello,

I am trying to  build a differential Transimpedence Amplifier with THS4531A.

I used a feedback resistor (which serves as Transimpedance) value of 20k in parallel with a compensation capacitor of 7.5pF

I used the pspice model for THS4531A in my Spectre simulations to check the stability. 

It gives me the phase margin ~ 72 degrees and Gain Margin ~ 16dB. which looks good enough to me.

My question is : Can I trust these spice models for the stability simulations I did in Spectre ?

regards,

Ashish

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Sensing high voltage over a barrier

February 26, 2019, 1:51 am
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Hi,

I need to sense line voltage over a barrier. The barrier is functional so I want to measure via a high resistance barrier. Does TI have special opamp/documentation for this?

I need to be small. space is an issue.

Thanks,

EVS

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INA225: Current sensing on high power bldc driver

February 26, 2019, 2:24 am
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Part Number:INA225

Hi,

I'm trying to build a bldc controler able to drive a 15kW motor...

I have trouble to get a coherant measure of current in each phase... I fact i am developping the controller board using a pre-existing powerboard to speed-up the task. But  this power board has only shunt resistors on each phase but no common shunt... and it is realy low resistors  (i mean pcb trace) about 50 micro-ohms...

I'm trying to get the rotor position using the inductance variation method, shortly I drive High to phase and the third is driven low and then reverse the phases...

Here you can find some pictures of waveform :

First pulse U and V are pushed to 30V and W is driven to 0V then in the secon pulse W is driver high end U and V are diven low...

The current is taken from the shunt resistor to an INA225 with G=100 and a ref voltage around 0.5V.

Currents : Yellow = phase U, blue = phase V and pink = phase W...

Is someone can explain me why in the first pulse I catch a current in every shunt ? I mean why the yelow one is following the other ones ??

Mosfet is off and I've done many simulations and I can't understand why the op amp amplify this ghost current...

Here is a schematic of one simulation with layout resistance of the bridge

I can' t explain what I see on the scope...

I'm pretty sure this current does not exist !

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LM7171: Overheating problem in inverting amplifier configuration

February 26, 2019, 2:50 am
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Part Number:LM7171

Dear All,

I have been using a OP07E amplifier in a inverting amplifier configuration and I understood the response to an AC signal. However when I changed the amplifier to the LM7171 the response was incorrect and the amp started to overheat. I intended to use the LM7171 due to its higher unity gain bandwidth. I have attached a diagram showing the circuit I made. Why does the LM7171 overheat in this configuration? Does the high speed ampllifier work in a different manner to the OP07 amp range?

Kind regards,

Conor Davidson

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AMC1301: AMC1301 output overshoot while VDD1 is power off.

February 26, 2019, 2:52 am
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Part Number:AMC1301

The AMC1301 VDD2=5V,

the normal situation is that when VDD1=5V,the output Pin6-7 should be 0V, when the VDD1= 0V, the output pin6-7 should be-2.5V.

while the AMC1301(15 pcs among 40 pcs amc1301 LOT 85TG4）were found that the output was turn to +2.5V first(Overshoot obviously) and then down to -2.5V when the VDD1 change from 5V to 0V, the output should change from 0 V to-2.5V directly. this  +2.5V over will cause fault implement.

most of the these MP amc1301 were OK, while this Lot(85TG4)was not OK.

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INA240: INA240-SEP, PWM rejection in Output

February 26, 2019, 4:44 am
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Part Number:INA240

Dear Team

I was designing a circuit with INA240-SEP.

However, I am facing a problem in the output pin of this IC. I am applying a modulated signal (12V to 0V) @ 200 Hz at the input pins and am using a 0.27 ohm shunt resistor. Now, in the output pin I am able to get a voltage signal that is directly proportional to the current consumed, however, this output is also modulated at the same duty cycle in which I have applied the signal. Moreover, I am getting spikes as well.

The datasheet of the IC mentions that it has good PWM rejection, but it isn’t doing so. Attached is my circuit diagram.

I seek your support, an early response from your side will be highly appreciable.

 

I thank you in anticipation and look forward to hearing from you.

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INA139-Q1: internal circuit question

February 26, 2019, 6:34 am
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Part Number:INA139-Q1

Hi team,

Our customer asked a question about INA139Q1.

Could you support to answer these questions?

1. I want to know the internal circuit between PIN 8 and PIN6 in INA139-Q1 for  DFMEA analysis. Could you share the internal circuit with us?

2.Will PIN 8 and PIN6 have chance to be a short situstion below the formula? When will this situation happen,if it happen, what is the impact?

Best Regards,

Nishimura

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LMH3401: LMH3401 maximizing output voltage for pulsed input

February 26, 2019, 11:54 am
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Part Number:LMH3401

Hello e2e,

Follow-on questions from https://e2e.ti.com/support/data-converters/f/73/p/772076/2857052

1) Please consider this circuit:
           _______         ___________
Signal----|       |--40Ω--|           |
          |LMH3401|       |ADC12DJ3200|
VDC--50Ω--|_______|--40Ω--|___________|
|
v

In my design I want the average voltage presented to the LMH3401 inputs to be different. That's because V_IN+ is not symmetric, i.e. the voltage duty cycle is far from 50%. In other words, the DC voltage of V_IN+ - V_IN- is far from 0. Does it cause problems in the amp to not have a balanced input like that? 

2) Please consider this circuit:
           _______     ___________
Signal----|       |---|           |
          |LMH3401|   |ADC12DJ3200|
VDC--50Ω--|_______|---|___________|
|
v

If one connects the LMH3401 V_OUT+- directly to ADC12DJ3200 INA+- without 40 Ohm resistors on a board (trace length < lambda / 10) thus bypassing the 40 Ohm resistive loss, would the 0.55 voltage loss from the 40 Ohm resistors be improved to ~1 in practice? Would this circuit work in practice for broadband inputs? What would be the deviations from specified performance?

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PGA308: Thermal Pad Connection for the DRK Package

February 26, 2019, 12:14 pm
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Part Number:PGA308

Hello,

The datasheet for the PGA308 does not mention what to connect the thermal pad connection to on the PCB. My guess is that either of these options will work but I would like to make sure:

  • Can the thermal pad be tied directly to ground?
  • Can the thermal pad be soldered to a floating copper plane?

Thanks,

John

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LOG114: Step response performance greatly differs from datasheet

February 26, 2019, 1:20 pm
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Part Number:LOG114

Hi!

I've got a problem with LOG114, it does not match submicrosecond step response time as it should according to datasheet. My scheme has +-5V dual supply, I2=2,5uA and I am getting submicrosecond responce times only in area of at list 1-10mA input currents. If I try 1uA to 100uA or 1uA to 1ma or 100uA to 1ma square pulse it shows response times (10 - 90% rise time) greater than 1,5 - 3us. Datasheet states that response time should be less than 0,15us. Is there any resonable explanation for that? Tried already replacing IC with another LOG114, got same results.

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How to build a current mirror with discrete components?

February 26, 2019, 2:17 pm
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Hi all,

    I am trying to build a current mirror circuit for my application, however, I can only do this with discrete components on a PCB, which I suspect it is possible since I have no control over the W and L of the MOS to have desired gain. So my questions are:

(1) Is it possible to build current mirror with discrete components ? How can I tune the gain ?

(2) Are there any current mirror ICs off-the-shelf that I can have a small current input and an amplified current output?

    Thank you for help!

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LH0094 (Obsolete Part) Sine Function As In National Semiconductor Application Note 637 (SNOA139)

February 26, 2019, 2:01 pm
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Is there any replacement for the LH0094 so that I could build the sine function circuit as  described in SNOA139?

Also acceptable would be a replacement for the AD639 (obsolete trigonometric function IC) although I don't think it is a TI or National Semiconductor part. 

Thanks for any help.

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MF10-N: MF10-N

February 26, 2019, 2:31 pm
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Part Number:MF10-N

I have a square wave of 400Hz and want to have a sine wave. Is this device suitable for that application (as the frequency is low)

I assume  LPF ?

Suggestions

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INA219: used on wide range power input

February 26, 2019, 8:25 pm
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Part Number:INA219

Hi Sirs,

Sorry to bother you.

Could you double check  if IN219 can be used on wide range power input(12V~24V)?

Because Intel got an information shows INA219 only can be used on fixed voltage input, otherwise the accuracy will be very poor.

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LMH6645: LMH6645 replacement

February 26, 2019, 11:44 pm
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OPA2314: About the noise of ADC collection circuit.

February 27, 2019, 12:26 am
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Part Number:OPA2314

Hello ! I use OPA2314 and piezo electric sensor to design a  device to collect pause walve signal. The  Schematic and noise image is liking the image down. I am wondering the possiable reasons acoouting for the noise.Would please help me. Throug searching the revelated documents.The frequency of pause walve is no more than 30Hz. Thanks for replying.

 

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INA226: Conversion behavior for Bus voltage only mode

February 27, 2019, 12:46 am
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Part Number:INA226

Hello

I would like to cralfy about measurment sequence of INA226.

If i set Bus voltage only setting to the MODE bits of configuretion register, The device does not measure shunt voltage? or the device internal sequence measures shunt voltage but ignored?

For example, if I set Bus Voltage Triggered,  Bus voltage Conversion time = 1.1ms and Averaging =4, Can I get the bus voltage result in 4.4ms?

Best regards,

Tetsuro

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OPA549: E/S function

February 27, 2019, 1:46 am
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Part Number:OPA549

Hello,

I have a question about E/S function.

When E/S pin is changed from Hi to Low,
does the output become zero(GND level)?

It is written that the output is disabled and shut down in 1µs
in the datasheet.

Is this the meaning that output will be high impedance, not zero?


Best regards,
itabi

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