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Impedance Balancing

October 31, 2019, 2:50 pm
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My apologies if this isn't the most appropriate forum to ask this question, but I have found the response from users on this form to be extremely helpful in the past with my electrical questions.

I am new to impedance balancing so bear with me. I have a transmitter and receiver with 2000 meters of electrical cable connecting the two. The signal I am transmitting is a 3.3 volt digital signal. I am trying to impedance balance this network and a bit confused where to hook up my VNA.  I drew a diagram below, is this correct?  If I understand it, my VNA connects to the transmitter circuit while it is connected to the 2000 m transmission cable, which is then connected to the receiving circuit. Using my VNA and a Smith Chart, I will impedance balance the TX circuit with some "L" network including a certain value inductor and capacitor.  After that is balanced on the VNA, I connect my VNA at the receiving end and do the same type of impedance balance.

Does this make sense or am I going about this wrong?  Thanks for any input anyone has.

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BQ40Z50-R2: How to safely test a new board

October 31, 2019, 3:31 pm
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Part Number: BQ40Z50-R2

Hi,

I'd like to design a board for the bq40z50-R2 to build my own lithium battery pack, but I am still unsure how can I test it safely.

I am worried that an error in my board design or in the configuration of the bq40z50 might cause a short circuit or some other unsafe condition to the batteries.

I was thinking of buying for the first tests a 2s or 3s commercial Lithium battery pack with protection (short circuit, overvoltage, undervoltage per cell,…) already integrated (unspecified IC).

I am unsure whether that protection circuit might interfere with the normal operation (measurement accuracy,…) of the bq40z50, invalidating the test.

I could also use stricter protection thresholds for the bq40z50:

For example I'd set 4.23V for overvoltage on the bq40z50, whereas the protection IC in the commercial battery pack is set for 4.35V. This way I'd see if the bq40z50 sets the appropriate flag during an overvoltage test.

During such a test, can I also use a multimeter to monitor the batteries voltage or would this also interfere with the protection ICs?

 

Once these first tests are done, I'd proceed using the designated batteries for my battery pack (branded 18650 Li-Ion or RC LiPo without protection IC already in them).

 

Could this work or do you suggest an other procedure/hardware?

 

I am doing this as private person (as a maker), so I have no access to costly equipment or facilities (or chemical fuses).

 

Thanks in advance for you help

Sincerely

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UCC28950: Worst Case Power Dissipation for clamp diodes Db and Dc

October 31, 2019, 3:16 pm
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Part Number: UCC28950

In the UCC28950 datasheet section 8.2.2.5 says the maximum power dissipation for clamping diodes Db and Dc is given as  = .5*Ls*I^2prms*Fsw   

What are the conditions where this worst case power dissipation can occur? 

The section in the datasheet says to use MURS360 SMC rectifiers.  However, based on the calculation for maximum power dissipation the power can be well over 10 watts which is not going to work with the diodes recommended.  Please advise!!

We have observed that certain conditions (abnormally low low output voltage operation) these rectifiers can overheat and fail.  Is this expected?  How can this be mitigated?

  

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BQ2970: Modifying OVP/UVP thresholds

October 31, 2019, 4:42 pm
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Part Number: BQ2970

Hello,

I have a battery cell which has non-standard voltage (4.0 V to 5.5 V). My question is if a standard BQ29700 can be used with a voltage divider on the BAT pin to divide down battery voltage to what is within range of the chip. Will adding a voltage divider on this pin cause any problems? If so, can any other battery protectors be recommended that have this voltage range for UVP/OVP?

Thanks,


Alex

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LM25141-Q1: Adjustable output controlled by DAC output

October 31, 2019, 4:53 pm
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Part Number: LM25141-Q1

Hello experts,

I have question for LM21541-Q1.
This device has two mode, fixed output mode(3.3V, 5V) and adjustable output mode.
In adjustable output mode, I would like to make some output voltage with VDAC output like as this picture.(http://www.ti.com/lit/an/slva861/slva861.pdf)
Is it possible?
Thanks and best regards,
Ryo Akashi
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TPS7A05: Asking for the recommendation on the TPS7A0530PDQNR

October 31, 2019, 5:05 pm
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Part Number: TPS7A05

Hi Team,

Customer is studying TPS7A0530PDQNR and request for the following condition result.

Would you please help for the data collection?

Minimum input voltage to maintain regulated 3.00V output at no load:

Minimum input voltage to maintain regulated 3.00V output at 100uA load

Input current at 80uA load (at both 3.7V and 4.2V inputs)

Apply 3.7V to the input. Ground the Enable pin to disable the LDO. Using a power supply, apply voltage to the LDO output and increase the voltage slowly from 0.0V to 3.7V in 0.3V steps. Record the current that enters to the LDO output at each voltage step.

Apply 3.7V to the input. Connect Vin to the Enable pin to Enable the LDO. Using a power supply, apply voltage to the LDO output and increase the voltage slowly from 0.0V to 3.7V in 0.3V steps. Record the current that enters to the LDO output at each voltage step.

Measure output voltage droop at 3.3V input and 100uA load

Input Current vs Grounding current, CE= High, without load, while Vin =3.3V and 4.5V

Input Current vs Grounding current, CE= High, with 100uA load, while Vin = 3.3V and 4.5V

 

 

 

BR,

SHH

 

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BQ2980: Modifying OVP/UVP thresholds

October 31, 2019, 5:17 pm
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Part Number: BQ2980

Hello,

I am wondering if a voltage divider on the BAT pin can be used to specify different OVP/UVP thresholds than the options available pre-programmed. Specifically, I am trying to find a protector IC for a non-standard battery chemistry that has a voltage range of 3.2 V to 5.5 V which would work perfectly with the BQ298000 and its voltage range of 2.6 V to 4.475 V and a divide by 1.23 divider. Any reason not to try this?

Thanks,


Alex

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UCC256301: UCC256301 vs UCC25640x

October 31, 2019, 6:18 pm
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Part Number: UCC256301

Hi Sir 

If new project ,could we use UCC25640x to instead UCC256301 ?

But I don't see UCC256401 on TI website ? Could you help to double confirm ,which P/N could instead UCC256301

Thanks

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TL1431-SP: Stability - Output Capacitance requirement ?

October 31, 2019, 6:24 pm
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Part Number: TL1431-SP

I will be using SMD # 5962R9962001VHA.  My application is the following:

Power Supply input 3.3V (+/-4% tolerance), TL1431 configured for 3V output.

The TL431.xlsx tool calculator suggest R1 = 61.9-Ohms, R2 = 1.24-K and R3 = 6.19-K and an output capacitance to maintain stability - either less than 6200-pF or greater than 3.3-uF.

I will use the 3V reference to power TI, ADC (5962R0722701VZA) and DAC (5962R0722602VZA)...powering VA & VD pins of each with the decoupling as indicated in the DS (VA with 0.1-uF and VD with RCC from VA).  I will have another 0.5-mA of loading.  Note, both the ADC and DAC will be monitoring and setting DC levels no dynamic requirements).

Question:

The output capacitor requirement indicated in the excel tool calculator is not discussed in the datasheet.  As such I am not confident on how serious this capacitor will be in my design ?

I have limited real estate and prefer to have further feedback on the concern for stability in regard to my application.  Can you provide further feedback on this.

Regards,

Sean

regards,

Sean

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BQ76940: 8KV air gap ESD fail

October 31, 2019, 7:17 pm
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Part Number: BQ76940

Dear TI Experts,

My customer failed ESD test under 8KV air gap throught P+/P- pad, the phenomenon is regout no output.  BQ76940 can recover after reset, could you give some advices how to improve this?

Below is PCB layout. Thanks.

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TPS2511: My circuit can not charge IPAD at 2A can you help review my circuit?

October 31, 2019, 7:18 pm
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Part Number: TPS2511

Hi 

My circuit can not charge IPAD at 2A can you help review my circuit below? Thanks!

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LM5045: traditional hard switching full bridge VS phase shift full bridge in 54V input

October 31, 2019, 7:27 pm
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Part Number: LM5045

Hi Support team 

may i have your help to compare w/  traditional hard switching full bridge VS phase shift full bridge in 54V input & 1KW application 

which one have better efficiency and why?

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CSD16570Q5B: Why CSD16570Q5B is not designed for switching applications?

October 31, 2019, 7:41 pm
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Part Number: CSD16570Q5B

Hi Pro. :

I am looking for a low Rds(on) MOS to implement MOS relay. 

But see the warring description in datasheet. Why CSD16570Q5B is not designed for switching applications? 

The MOS as relay in my design, operation frequency <1KHz. Bypass about DC 25A current.

Can CSD16570Q5B be used?  Could I have recommend solution?

Thank you.

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LM5170-Q1: Voltage regulation

October 31, 2019, 7:47 pm
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Part Number: LM5170-Q1

Hello,

I have looked at the datasheet but cannot see how the output voltages are regulated?

Is this ic for fixed 12V to 48V & 48V to 12V converter?

Can any other voltages be selected?

If no, can you recommend an interleaved bi-directional (buck-boost) current mode control ic that can do say 3V to 8V and 8V to 3V

Many Thanks

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LMZM33603: About Inverting buck-boost (IBB) topology

October 31, 2019, 7:59 pm
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Part Number: LMZM33603

Hi Team,

 

I would like to use LMZM33603 for Inverting buck-boost (IBB) topology.

Then, I understand that I can connect PGND pin and AGND pin.

 

Because, the device has AGND and PGND are internally tied in this device.

Please refer to the following E2E thread.

https://e2e.ti.com/support/power-management/f/196/t/754416?tisearch=e2e-quicksearch&keymatch=LMZM33603

 

Is my understanding correct?

And, could you please let us know if you have any concern?


 

[Supplementary explanation]

By the way, according to datasheet, “Do not connect this pin to PGND”.

This comment is advice for normal operation(buck topology).

Therefore, I understand that it is not applicable in IBB topology.

 

 

Regards,

Hide

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TPS63810

October 31, 2019, 8:13 pm
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(Please visit the site to view this file)

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LM25118EVAL: About oscillation of output voltage

October 31, 2019, 8:38 pm
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Part Number: LM25118EVAL

Hello.
Input voltage (6V) was applied after connecting load resistance 12Ω using LM25118EVAL.
The output voltage oscillates and does not operate normally.

I use it with the load connected.
Please tell me the cause of oscillation and the countermeasures.
The circuit constant of EVAL remains the original.

Please.

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TPS82140: TPS82140SILT - Maximum Output Capacitance

October 31, 2019, 9:41 pm
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Part Number: TPS82140

Hello,

Looking through the data sheet I do not see anything that helps me understand the maximum capacitance on the load side. My objective is to use this device to power a modem which is 5V, but has a peak current of about 500mA. However, the input supply is a Li battery limited to 400mA max peaks, and much lower at -30C.

Since the TPS82140SILT can supply that current comfortably,  can a super-capacitor of value 2.5F be added to the output safely?  The TPS82140SILT will be powered up for at least 20 seconds before transmitting to allow the supercap to be charged, provided it can be used on the output side. When the modem is enabled on, it has a nominal current draw of about 100mA.

What are the constraints or considerations here, if any?

Thanks!

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TPS51216: How to measure gain and phase margin with using an impedance analyzer

October 31, 2019, 9:49 pm
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Part Number: TPS51216

Regarding our circuit with TPS51216 , could you let us know how to measure gain and phase
margin with using an impedance analyzer such as ZGA equipment(NF corp.) ?
We believe the environment of the measurement as below is no problem.
Could you provide opinion?

(Please visit the site to view this file)

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TPS65911: Need PMIC for FPGA and Processor

October 31, 2019, 9:50 pm
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Part Number: TPS65911

  Please refer below details which is taken from PMIC “TPS65911” datasheet. 

 In this table the recommended PMIC device for 66AK2G02 is TPS659118.

We are using 66AK2G12 processor. As per your recommendation, can we use TPS65911A for 66AK2G12 part.?

 Also there is no separate datasheet available for TPS659118 & TPS65911A.

Provide ordering information for the part “TPS65911”

In addition to this, we need PMIC for FPGA – Arria V  Part “5AGXMB1”

Please provide your suggestion.

 

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