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AMC1200: reliability data

January 12, 2018, 7:35 am
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Part Number:AMC1200

Hello every one

I'm looking for the FIT rate of AMC1200BDUB.

I didn't found it on TI site, some one can help me?

thank you

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TINA/Spice/TLV8542: Spice Model Misleading and Wrong

January 15, 2018, 8:21 am
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Part Number:TLV8542

Tool/software:TINA-TI or Spice Models

Hello Precision Amplifiers Forum,

This may belong in the Simulations and Models Forum, but I believe this forum will best answer my immediate question/concern.

I have been very hard pressed to find a model of the TLV8542, simply because I need it in some sort of library/component form so that I can use it in a circuit board design.  The only models offered on the TI site are a .LIB file, which is the library extension for KiCad.  When attempting to import this LIB file into KiCad there is an error that is just a Chinese character.  The only other option is the SPICE model which I wouldn't mind having because I like the ability to model things in SPICE before building them.

My second issue is with this SPICE model.   Model is a strong word, it is technically only a schematic (.TSC), but when this schematic is opened there is a basic circuit with a component labeled as TLV8542.  I assume this is where the data from the TLV8542 datasheet was generated, since there is also a graph representing Gain vs Frequency.  The problem is that in this SPICE schematic this component is NOT TLV8542, under the properties it is LMP8672.

The question: is LMP8672 even close to a valid representation for TLV8542?  I would argue that the simple fact that LMP8672 is not RRIO and TLV8542 is RRIO would massively impact all of the simulated models.

I need to use TLV8542 very specifically in an RRIO setting, and I would like to model it in SPICE using the most basic Bubba Oscillator circuit.  Are there any suggestions on components that actually exist in SPICE that would be viable representations of the TLV8542?

Best regards,

Michael Slitts

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OPA330: Input Impedance

January 15, 2018, 8:24 am
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Part Number:OPA330

I am having a little difficulty understanding the impedance specifications. The data sheet for the OPA330 does not list any impedance values.

I did read a post in E2E that explained that you could calculate the common-mode impedance of an op amp (OPA330) by taking the change in the common mode voltage and dividing it by the change in the in the bias current. Many data sheets have a graph of this so calculating this is possible. I have done this calculation and it appears that the common-mode impedance of the OPA330 is (5V/5pA=) 1000Gohms. Is this the correct approach?

 The issue that I am having is that the customer is asking for the differential impedance. This is not listed, but is there a way to calculate this? I did see a post that stated that if the op amp was produced using a CMOS process that you could estimate that the differential impedance would be 100Mohms and the common-mode impedance would be 6000Gohms. I am not sure if this applies to these chopper driven op amps like the OPA330. Can you elaborate at all on this? Are there any calculations available? Are there any impedance specifications available?

 Thanks for your help with this!

Richard Elmquist

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LMP7731: Input capacitance

January 15, 2018, 11:46 pm
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Part Number:LMP7731

Where I can get the value of input capacitance for this OpAmp?
I want compare it with ADA4528-1 and this characteristic is important in an application.

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LMP7721: Gamma radiation sensor

January 16, 2018, 11:41 am
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Part Number:LMP7721

Hello,

I have inherited this radiation detection board design at work. None of the original designers are with us and very little documentation exists. The design has been through several revisions and still 30% of the boards do not work as desired, or they work at our facility when we test them but do not work at customer's site. 

A PIN diode (PDB-C156-ND) is used as the sensor, followed by an LMP7721 as the first stage transimpedance amplifier. I first suspected layout and noise issues, because there were no guard rings on the board. The whole circuit is enclosed in an aluminum shield, but no guard rings. As I investigated more, now I suspect the feedback capacitor and resistors values as well. 

This stage is followed by a band-pass filter. Of course I found cut-off frequency settings to be a little off and as I changed the values performance improved significantly. 

Though I still cannot figure out how previous designers of this board calculated capacitor and resistor values for LMP7721, and I need a second opinion with that since my own calculations yield different values.

You can see the LMP7721 part of the circuit below, where;

C19 = 0.6pF, R3 = 10Mohm, R17 = 100Kohm & R18 = 49.9Kohm

Using equation 8 from the datasheet (page 19) and assuming that;

Cs = Cin + Cj + Cstray, where Cin is LMP7721 input capacitance (11pF), Cj is junction capacitance of photodiode (10pF) and assuming 3pF for any stray capacitance. I have Cf ~= 0.4pF. Where if I Do not change R17 & R18, then C19 should be 0.8pF, or if I change R17 & R18 to 50K and 10K, C19 nan be 2pF.

So I have two questions;

1- Do you think the current values will work fine and I should just leave them the way they are, or shall I replace them with any of these configurations I mentioned above?

2- Do you suggest that I change the layout and add a guard ring for LMP7721?

Thanks for your help,

May Varza

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LMH6401: input common-mode voltage

January 16, 2018, 6:08 pm
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Part Number:LMH6401

Urgently need clarification of the following Electrical Characteristics,  Vicm, Viclr, Vichr, found in the datasheet;   literal interpretation implies there is dc common mode voltage at each input pin.

Vicm states that is is self-biased to mid-supply (in our case 2.5V DC);    Our concern is interference with the DC common mode voltage at the stage driving the LMH6401;  are dc blocking capacitors

required in this case ?   Is there truly Vicm = 2.5V at each input pin ?   Thank you

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AMC1200: AMC1200BDWV

January 16, 2018, 6:52 pm
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Part Number:AMC1200

Dear,

I have a question about AMC1200BDWV datasheet description.

3.3V Operation on Low-side  

Does it mean it only can be used on low side? We want to replace ACPL-C790-500E with AMC1200. Could you give some advice? 

Thanks!

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TLE2061M: Thermal Impedance data

January 17, 2018, 7:11 am
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Part Number:TLE2061M

Hi,

Can you please provide the following thermal impedance data for TLE2061MD?

1. Junction to lead (pin 4 and pin 7)

2. Junction to Case (plastic body)

Thanks,

Shihab.

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OPA192: Long term effect of output saturation

January 17, 2018, 8:12 am
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Part Number:OPA192

Is there any long term harm to driving the OPA192 or OPA4192 so that the output drives to the negative rail? I see from the data sheet that there is a recovery time associated with overloading and this is fine. My concern is with any long term affect on offset voltage. The amplifier would be operated as non-inverting with a gain of 10 and the input CM will not hit either rail.

Thanks,

Tom

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LM2907-N: NPN flow sensor circuit for LM2907-N

January 17, 2018, 9:24 am
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Part Number:LM2907-N

Hello,

I want to convert the frequency signal from this flow sensor:

to a voltage from 0-10V

The input voltage is 12V DC

The max frequency is 80Hz the normal operating frequenc is 48,85Hz

At the moment i put an Pull-Up Resistor parallel to the NPN to make a PNP. The Amplitude Voltage is max 9,2V

Can someone help me, i don`t know how the circuit design for the input at pin 1, must look like with an open collector (or the PNP)? And how i can calculate then R1, C1 and C2 or other needed resistors?

I calculatet for the regular minimum component tacometer:

R1 = 100K Ohm
C1 = 0,1µF
C2 = 10µF

i get an Vout of 9,6V at 80Hz.

Thanks to everyone!

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OPA128: Top and Side Markings Required

January 17, 2018, 12:45 pm
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Part Number:OPA128

Hello TI,

I need the Top and Side Markings for the OPA128SM.

Can you send us a reference picture or diagrams of the CAN package top and side markings?

 We are finding different markings on these parts within each date code.  We want to know what these markings mean.

 So far we can only find he generic package outline for reference.

Thanks,

Dan

 

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LF398-N: What is advantage of using two of these sample-hold circuits in tandem?

January 17, 2018, 3:01 pm
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Part Number:LF398-N

Hello,

On page 20 of the datasheet for this part shows an example of typical applications, titled "Fast Acquisition, Low Droop Sample and Hold". The datasheet I'm looking at is:

http://www.ti.com/lit/ds/symlink/lf198-n.pdf

In this example, there are two LF398s in tandem. Could you please explain how this achieves "fast acquisition" and "low droop" compared to doing it with a single LF398?

Thank you,

Jae Jeon

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LMP91200: amplifier for differential pH sensor

January 17, 2018, 3:18 pm
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Part Number:LMP91200

I am aware of the LMP91200. However, we need to use a fully differential pH probe - see attached diagram - which has the contained liquid as its ground reference. Could you suggest an appropriate low bias matched (dual probably works) diff amp (or other circuit/part) to attain similar results as those of the 91200? Thank you

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PGA280: Schottky diode spec

January 18, 2018, 1:52 am
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Part Number:PGA280

Hi,

I would like you to cofirm about below.

* Which schottky diode should be selected ?

According to datasheet of PGA280, there is following description.

VSN is connected to the substrate; therefore, the voltage at VSON or DGND must not turn on the substrate
diode to VSN. Use external Schottky diodes from VSON to VSN and from DGND to VSN (refer to Figure 50) to
prevent such a condition.

So, I believe user need to implement schottky diode. However, there is no description about required spec of this schottly diode.

How many current pulse(or continuous current) will cause ?

Or, if you have recommended schottky diode, could you please let me know ?

Best regards,

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LMP91200: ORP SENSING USING LMP91200 IC

January 18, 2018, 2:44 am
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Part Number:LMP91200

Hello Sir

I am using LMP91200 IC for pH as well as ORP sensing.

For pH sensing range is -500 mV to +500 mV, it works fine.

But for ORP sensing Range is -2000mV to +2000mV,Can I directly apply this -2000mV to + 2000mV. to input pins of LMP91200IC(i.e; Pin no 5 & Pin  no. 8).

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XTR115: XTR115

January 14, 2018, 2:17 am
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Part Number:XTR115

Hi,

I have XTR115  but I don't have instrumentation amplifier.I want to check 4-20mA current at the output of XTR115.So it is possible to check by applying 40-200uA at IN pin with series resistance.

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XTR115: XTR115

January 14, 2018, 2:31 am
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Part Number:XTR115

Hi,

I have XTR115 but I don't have Instrumentation amplifier. I want to check 4-20mA current at output of XTR115.So it is ossible to check by applying sufficient current at IN pin with series resistance.

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PGA308: Why PGA308 OTP registers automatically become garbled?

January 15, 2018, 8:49 pm
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Part Number:PGA308

Hi team,

Our customer from deyi support is using our PGA308 in their sensor system. Schematic is as follows:

They made 30 several sensors, there have been four sensors of them has the problem of OPT register garbled.

Could you please help to analyze the problem?

Thanks & best regards,

Alix.

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XTR115: Loop Current Changes with Loop voltage

January 18, 2018, 12:40 pm
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Part Number:XTR115

Hello,

I am using XTR115 in my application and the circuit works fine (except some non linearity) with 4 to 20mA output. when I changed Vloop from 16V to 24V, the DC loop current jumped to 30mA from 4mA. 

The other question I have is, if Rload always required or we can just measure current using a meter connected in sereies with Vloop.

Thanks.

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LMP91000: Automotive CO2 sensor application.

January 18, 2018, 11:49 pm
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Part Number:LMP91000

Dear team,

My customer want to know about Automotive CO2 sensor application.  

1. Is there any AFE solution of Automotive CO2 sensor application? I have been finding AFE of CO2 sensor but there Is no automotive version.

2. For CO2 sensor, would you recommend vendor of CO2 sensor for automotive application(temperature grade : -40C ~ 85C)? At LMP91000 TI design(Gas Sensor Platform Reference Design), Alphasense sensor is used but temp grade is up to 50C.

Please let me know your opinion.

Thank you.  

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