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OPA2234 Input Overshoot during lightning event

July 21, 2016, 5:31 am
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Hi

I plan to use the OPA2234U single supplied (+12V) in an application to measure a temperature (PT100).

During a lightning event (750V peak) the input filter limits the Voltage at the Input pins up to ~21V for a short (~2ms) time.

The absolute maximum ratings of OPA2234 state an input voltage of (V+)+0.7V. Because of the voltage I assume that the input is internally protected by a diode.

  • Is it possible, that the inputs can withstand such a voltage?
  • Does the current has to be limited (no value is stated in the Datasheet)?

Other lightning protection solutions will lead to a greater decease of accuracy due to leakage currents.

Below is a simulation of the voltage curve:

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SLAU502 -High Side Voltage to Current converter

July 21, 2016, 5:41 am
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Reposting in the correct Forum. Original request from Joseph St. Armour

-------------------------------------------------------------------------------------------------

I am looking at this circuit from TI and would like to modify it to become an LED current source.  

Ideally, I'd like to make a voltage controlled LED current source with this. The output LED load may vary in total voltage drop and VCC will swing to keep the minimal overhead required but reduce the power dissipation in the mosfet when the load changes. 

I've modified the TINA model of the circuit for 24V VCC, and 1A output current, but the circuit does not behave as expected. I've changed to the OPA2188 opamp for the higher supply current and adjusted the resistors based on this current according to the design document.

The output does not seem to be acting like a current source - if VCC is changed, the output current changes. If the load resistance changes, the output current changes. I can't seem to find the reason for this behavior.

Is this circuit inappropriate for what I am trying to do?

I'd appreciate any advise that could be given here. Thanks in advance.
Precision_current_source_1A.TSC

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AD SSM2164 and NEC C4574G replacement/upgrades

July 21, 2016, 8:49 am
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I have spend the last year rebuilding cip amps and am finding VCAs and opamps are just going bad aside from caps drying out. Contending with finding replacements has been an issue as most of them are no longer available. I have come to trust TI and Burr Brown over the years with my audio and would like to find a replacement. 

Thank You in advance. 

Jesse

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OPA320 : Input impedance

July 21, 2016, 8:02 pm
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To whom it may concern.

Our customer want to know input impedance.

There is no specification of input impedance in this datasheet but
input bias current is specified.

Can our customer assume input impedance using input bias current?

Your reply would be appreciated.
Thanks and best regards.

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AFE032 communication sequence

July 22, 2016, 1:32 am
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Hello,

I am a student of the Friedrich Alexander Universität (FAU), Erlangen, Germany. I am doing a thesis with the sensor's department. I am working with the AFE032 which will receive commands from a microcontroller and it will send the data to the power line, also the other way round, read from the power line and send it to the microcontroller...

I would like to know if there is any example of communication between the micro (using the SPI mode) and the AFE032 and the power line...also any example reading from the power line..

which pin are the one who transmit to the power line? (pin 43,42) is that right?

and to read from the power line is the pin 18?

my design in resume, is a microcontroller who sends the data to the AFE032 and this send the data to the power line, then, another AFE032 take the data from the powerline and send it to another micro (using a 24VDC power line)

thanks and best regards,

Andres.

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TLV246x output delay

July 22, 2016, 5:23 am
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Hi suppoer member,

My customer want to use TLV246x.

More than 1us output delay is observed at original circuit.

However offset applied input circuit isn't observed such delay.

What is the reason?

Attached documents show that.

Regards, Hirotaka Inoue(Please visit the site to view this file)(Please visit the site to view this file)(Please visit the site to view this file)

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pls check my triangular-wave generator designed by guide of TI'S DOC, the jitter of output wave is large,how to deal with it

July 21, 2016, 6:25 pm
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my design follow the guidance of TI'S DOC:ZHCU066-June 2013 by John Caldwell,using TI 's comps OPA2365 and tlv3502;

on my board, the jitter of tri-wave is so bad ,as a result,the backward PWM wave is not qualified.

any guys here pls give me some advise,many tks.

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OPA130, OPA2130 Power Dissipation

July 22, 2016, 9:32 am
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Hello,

What is the proper way to calculate power dissipation of the OPA130 (or the dual amplifier OPA2130 - I figure it's whatever the OPA130 method is and multiplied by two)?

Thanks

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Technical support

July 22, 2016, 7:35 pm
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Good evening everyone!


Congratulations to professionals of Texas Instruments!

Appropriate a report on the Texas Instruments service experience.

In july 13, 5:24:00 PM I requested 2 units LMP91000SDE / NOPB-Configurable AFE Potentiostat for Low-Power Chemical Sensing Applications.

In july 18, at around 04:00:00 PM I received the order, and to my surprise had 2 antistatic envelopes, only 1 of them was empty. I received only one chip having paid USD $ 20.99 regarding 2 chips.

On the same day, 7/18/2016 5:38:12 PM, I contacted support TI store (store.ti.com/contactus.aspx) detailing and explaining the situation.

The 07:38:00 PM in the same day, I received an automatic message informing the appropriate protocol and forwards with all the data I had provided.

On July 19, at 03:03:00 PM I received the Texas holder return thanking the contact and stating that a new order had been generated with the appropriate number, and that would not be charged any amount for sending the same product.

It seems to be highly relevant this respect, seriousness and honesty of a company towards its customers.

This attitude of Texas Instruments proves what I already knew:

Texas is the best company of this branch!

Thank you very much!

Regards,

Luiz.

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LM331(V-F) Equivalent SMD Part

July 24, 2016, 11:38 pm
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Sir,

   We are using LM331 V2F ,but we required LM331 equivalent smd part or any alternative part in smd package.

 please provide the availability of item.

Regards,

S.Geetha vani.

TEMC.

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LMP90077 General Questions

July 25, 2016, 6:06 am
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Hi,

I have questions about the LMP90077.

1. The Resolution is 16 bit, which makes 0 - 65536 values. I want to use the device single ended. Now the datasheet Figure 71 shows that the MSB seems to be reserved for the sign + or minus... Also the ADC Calcuation in 10.1.3 gives me a maximum of 32768 for VINP = 5V; VINN = 0V. Now i wonder how to measure 16bit single ended ?

2. I did some testing with the WEBENCH Designer for this chip. If gives me values of 20bits ENOB and 17.5 bits NFR. How to interpret these values?

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OPA625 input bias and offset current in SPICE model

July 25, 2016, 3:27 pm
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According to OPA625 datasheet the nominal input bias current in High-Drive mode is +2uA, and the input offset current is 20nA. While simulating the SPICE model of OPA625 in TINA-TI I've noticed that the input bias current is being +2uA into the positive input and -2uA into the negative input. This makes the input current to be 4uA, which is in direct contradiction with Ibias and Ioffset values defined in the datasheet. Seems like a problem in the model, but I would like to be sure. The device is being simulated in the same conditions defined in the datasheet:  V+ = 5 V, V– = 0 V, MODE pin connected to V– pin, VCOM = VO = 2.5 V, gain (G) = 1, RF = 1 kΩ, CF = 2.7 pF, CLOAD = 20 pF, and RLOAD = 2 kΩ connected to 2.5 V.

Please let me know if the problem is in the model, the datasheet or in my understanding.

Thank you

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Latent Failures of OPA2211AIDDA

July 25, 2016, 10:39 pm
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Hi Apps Support,

We are testing a custom Test Interface Unit that has several OPA2211 cascaded configurations.  Originally the default test plan did not take into consideration the voltage follower configuration and forced input voltages, while inadvertently applying voltage on the output of the previous amplifier.  Would the short test time, no more than 1 second, damage the device?  The failure rate of the devices is reported to be ~2% when the customer has received the boards.

This configuration and test resulted in atleast one failed U3-1 reference designator after shipment.  The Supplies are set to +/-15V and Inputs during testing of U4-1-B Vin+ is forced to 5.2V.  U4-1-B was tested after U3-1.

The following is part of a band-stop filter. 2 boards were reported to have failing devices within this configuration.  Again supplies are set to +/-15V and inputs were forced to 5.2V

Any other advice?  Or guidance to prevent damage during test?

Thanks,

Glen V.

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Does anyone know the output noise voltage density of ina129?

July 26, 2016, 7:39 am
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Does anyone know the output noise voltage density of ina129? I want  to calculate the output noise and compare it to ina188.

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op amp internal input protection

July 26, 2016, 2:53 pm
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I need an op amp with dual supplies 12V to -12V and has input overvoltage protection (30V to -30V) and also has protection against applying an input voltage before power up. Will OPA192 do it? If not, is there such a thing? Preferably SMD.

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PGA204 PIN Connection

July 26, 2016, 9:29 pm
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Hello ，

How should I connect the PIN1/PIN6/PIN7/PIN9 , if I don't need adjust the offset volatge of amplifier ?

From the following diagram , if we need to leave  it floating?


It seems the part is very old and its datasheet is not as well as the style TI used now .

Thanks.

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regarding noise in output of differential configuration of amplifier{OPA197}

July 26, 2016, 11:17 pm
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i am switching voltage levels of 32 channel  of a 32 channel multiplexers with the switching speed 20 ms/channel. The range of voltage is 0v to 15 volt..

 1st Stage:   then after i am passing voltage level through  unity gain buffer stage [OPA197]. 2nd Stage then after to reduce the voltage i am using OPA197 in differential configuration.

problem.

1) after unity gain stage i have 40 mV peak to peak noise(HIGH FREQUENCY) in my dc voltage level.
 but after deferential amplifier stage it increase to 200 mV peak to peak.


i tried to sort it out using a low pass filter but fail.

here below is my circuit

one thing i observed that the noise is more in low voltage levels such as 200mV 150 mV

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LMP7300 hysteresis problem

July 27, 2016, 3:22 am
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Hi ,

    I encountered a problem when I used the LMP7300. As illustrated in the following Fig, LMP7300 monitors the bus voltage. I set the Positive Hysteresis is zero, while the Negative Hysteresis is Vref*R11/(R11+R17) = 122mV, which is less than max hysteresis 130mV. However, when I turn up the Vin makes the voltage of input Pin -IN is larger than Vref, the output is still in high voltage. It can not work. When I tied the Pin HYSTN to Vref, It can work well. So I'm doubtful that the key of problem is the hsysteresis setting.

    Pls help me find the problem. Thx!

    ps:sorry for my poor Engilsh.

 

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TL972 - output source current and output sink current

July 27, 2016, 5:14 am
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Hi all

Would you mind if we ask TL972?

The datasheet shows as follows;
-Output sink current : 80mA
-Output source current : 1.4mA

If the output voltage is -5V to 5V sin wave form like as audio, in case of -5V, the current will be sink current 80mA.
If case of +5V, we guess that this is source current 1.4mA.
So, they are the same value.
Our customer would like to use 80mA both case, so is it possible?

Kind regards,

Hirotaka Matsumoto

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Help finding an opamp for my application

July 27, 2016, 7:54 am
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I need an opamp which can meet following specs.  Would someone suggest an op-amp?
Zin: high (preferably above 20 kOhm)

Zout: constant 50 Ohm.  Driving 50 ohms input of the 12-bit ADC.

freq. range: 100 kHz – 2.0 MHz (or 3.0 MHz)

THD < 1 % over above mentioned frequency range, Vout from 0 to 3Vrms and output RL of 50 ohms.

Vin: 0 – 3 V rms

Vout: 0 – 3 V rms
Thank you,

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