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TLV62569: Question on Pass Through Mode

May 23, 2019, 11:40 am
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Part Number:TLV62569

Hi team, 

From datasheet, I see that TLV62569 supports 100% duty cycle mode. I'm trying to understand if it makes sense to use this buck in front of a back up battery which will only turn on a few seconds. In this application, TLV output will be set to 3.8V and the battery voltage range is 3.3-4.2V. Assuming the lowest voltage of 3.3V, would the differential be too large for bypass mode? Also is this understanding correct that once VIN falls below VOUT, duty cycle will increase to 100% and there is no need for any further configuration to go into bypass mode?

Thank you!

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TPS65217: TPS65217. SYS pins floating

May 23, 2019, 11:49 am
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Part Number:TPS65217

Hello,

I have inherited a project since a team member left the company. I have just received the boards that were designed and noticed that the PMIC is not outputing any voltages. and the current consumption is 0.01A (apparently the PMIC is trying to do something but isn't able to).

After a review of the datasheet and the schematics this is what I noticed ... the SYS pins were left floating. According to the datasheet there are many pins that say "This pin must be connected to the SYS pin", so it's safe to assume that he made a mistake.

The thing is that I distinctly remember that the original person to design the board (another coleague who left) connected the sys pins together with the input 5V (the 5V that goes into AC pin) and of course the board didn't work properly, but I distinctly remember that in order to fix this and make the board work I took a box cutter and cut the connection between the sys pins and the 5 V input, isolating the SYS pins from the rest of the ciurcuit, just connecting them to each other and the board came to life (all those pins that require the 5 V were connected directly to the 5 V input).

I tried measuring one of its outputs (oin 20 connected to an inductor) and noticed that it tried to do something, it went up´to ~250 mV before going back to 0 V. This tells me that the PMIC is not dead, but there is something wrong.

Unfortunately this is not my project, I didn't design it, I was a member of the embedded software team, but now the hardware and embedded software teams are only 1 and now I have hardware responsabilities from designs that I didn't review nor designed. It seems that I have already answered my question ... that I probably need to cut up this board and do some wire ups to get it working, but i really need a second opinion before I start cutting anything.

If I go by my previous cut that isolated SYS pins from the rest of the circuit but left them connected to each other, then all I need to do is short those pins. But something tells me that I'm gonna have to cut many pins and wire everything up to get it working. Any advice?

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AFE2256 Power Supply recommendations

May 23, 2019, 1:10 pm
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Hi,

I am trying to support a customer request. They are using AFE2256 reference design and the product line recommends using a swicher with external DC-DC synchronization feature. The switching freq. must be exact integer multiple of scan time.

For 51.2 us scan time, switcher period must (51.2 us / N). For example, for scan time = 51.2 us, switcher with 1 us period (1MHz clock) is NOT ok. It will still give noisy lines as it is not exact integer multiple.

Keep option of LDO (TPS7A47?) after switcher for HV supply.

 The HV supply them can be given to level translator / buffer opamp for converting 0/3.3V logic to -10/20V levels.

Would you be able to recommend what TI parts should the customer be looking at based on the above description? Let me know if you have any questions

Thanks,

Soumya

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LMR33630: Test Question Only

May 23, 2019, 1:13 pm
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Part Number:LMR33630

This is a thread for only testing the subscription to E2E

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BQ2000T: BQ2000T missed pin

May 23, 2019, 1:24 pm
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Part Number:BQ2000T

Hello folks.

Into the BQ2000T datasheet (http://www.ti.com/lit/ds/symlink/bq2000t.pdf), inside 'Charge Current Control' section, in page 11, it is said:

"A hysteresis capacitor (CHYS) is required between the CMODpin and the SNS pin to add a healthy amount of hysteresis to the current sense signal"

Here goes my inquiry: There's no Cmod pin! Instead, there is a MOD pin! It's a mistyped word or I'm not seeing something?

Thanks

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BQ27510-G3: Problems with I2C subsequent subcommands

May 23, 2019, 2:19 pm
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Part Number:BQ27510-G3

Hello,

working with the BQ27510 I try to get the subsequent subcommands needed for some I2C commands right. As a test of the right implementation in the code I try to read the firmware version (command: 0x00, subcommand: 0x0002).

Here is a picture of the transmission:

First the general command code 0x00 is transmitted followed by the subcommand 0x0002. Then in the next transmission two bytes are read starting at register 0x00 where the previously requested data should now lie. The read data should be 0x0329 but it isn't. What am I doing wrong in the transmission?

Thanks in advance

Daniel

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BQ24232: Precharge safety timer doesn't activate

May 23, 2019, 12:21 pm
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Part Number:BQ24232

I am working to test the precharge safety timer on our BQ24232. The fast charge safety timer works as expected, and cuts off the charge current if the timer elapses. Currently I have an RTMR of 20 k-ohms, which translates to a nominal fast charge timeout of 160 mins. My test setup has the BQ24232 powered from a DC power supply, and a programmable load set to constant voltage mode hooked up to the BAT pins.

I have the load set to a voltage of 2.4 V. The charger seems to be in precharge because the charge current in this case is ~30 mA, and if I were to increase the voltage programmed across the load above 3 V, the charge current switches to the programmed fast charge current.

Given the 20 k-ohm timer programming resistor, the precharge safety timer should trigger after 16 mins. However, I have let it run for 4+ hours, and the precharge current never changes.

Any ideas for why the precharge timer is not kicking in, and for how I could debug it? Any ideas at all would be greatly appreciated.

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BQ27541: SOC occasionally drops to 0

May 23, 2019, 3:44 pm
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Part Number:BQ27541

Hello,

I have an issue that remaining capacity drops to 0% during discharge on some devices and log data as below.  What would possibly the cause and how to fix it? 

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LM25119: LM25119: transient load issue

May 23, 2019, 3:49 pm
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Part Number:LM25119

Dear Sir,

As below transient load waveform(output current 5A to 0A transient), output voltage overshoot too high over 200mV, 

Vin=20V ~ 36V,  Vo=12V/34A, circuit design interleaved mode(refer datasheet page 32 circuit)

DEM pin= floating(would improve light load efficiency)

RT=22Kohm(Fosc=220KHz); Output chock(L1= L2)=3.3uF, 

RAMP(R14+ C20) =73.2Kohm + 820pF ;  COPM1(R7 + C17 +C16)= 49K + 682pF + 100pF

Does L1=L2=3.3uF to low? 6.8uF is OK ?

Please you kindly review & provide suggestion(how to improve transient over-shoot)..

Thanks!

Steven

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LM25119: LM25119: transient of load issue

May 23, 2019, 3:56 pm
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Part Number:LM25119

Dear Sir,

As below transient load waveform(output current 5A to 0A transient), output voltage overshoot too high over 200mV, 

Vin=20V ~ 36V,  Vo=12V/34A, circuit design interleaved mode(refer datasheet page 32 circuit)

DEM pin= floating(would improve light load efficiency)

RT=22Kohm(Fosc=220KHz); Output chock(L1= L2)=3.3uF, 

RAMP(R14+ C20) =73.2Kohm + 820pF ;  COPM1(R7 + C17 +C16)= 49K + 682pF + 100pF

Does L1=L2=3.3uH to low? 6.8uH is OK ?

Please you kindly review & provide suggestion(how to improve transient over-shoot)..

Thanks!

Steven

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TINA/Spice/TPS79301EVM: TPS79301 output not correct

May 23, 2019, 5:41 pm
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Part Number:TPS79301EVM

Tool/software:TINA-TI or Spice Models

I'm trying to generate a 1.25V output in my circuit.  I've followed the equation from the data sheet (equation 4) and set R2 = 30.1kohm.  This results in a value for R1 of 624 for R1.  When I measure the output I'm getting a value of ~1.5V.  I've set C1 to 100pF per the recommendation in the paragraph below equation 4. 

When I probe the Fb pin I measure the same ~1.5V.  Is there any special advice for voltages near the feedback reference level? 

Separately I tried to load a simulation of the LDO in my configuration using TINA-TI only to find that the TPS79301 is not available by default.  The spice model provided by TI on the part webpage is encrypted which means I can't upload the model into TINA-TI.

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BQ78350-R1: How do I remove resistors from the EVM board?

May 23, 2019, 5:45 pm
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Part Number:BQ78350-R1

Hi

I'm using the bq76930 EVM board to develop a BMS solution for an 8 cell battery pack.  The Users Guide contains instructions for configuration of the board to support 8 cells, including instructions to remove some Input and Balance FET Gate Resistors.  Before I go and hack into my board, I just wanted to check how you would recommend doing this.  Does it literally mean to unsolder and remove the SMD resistors?  I'm just a bit concerned that I might not be able to neatly remove such small devices from the board.  Is there some technique(s) you can recommend?

Thanks

Mike

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LM317: Dropout operatin of LM317

May 23, 2019, 6:10 pm
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Part Number:LM317

Hi

I have a question about dropout mode of LM317.
If Vin belowed Vout, does Vout track Vin or become 0V?

Best regards,
Yokota
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LP8863-Q1: Power-Line FET gate drive (SD pin) voltage

May 23, 2019, 6:11 pm
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Part Number:LP8863-Q1

Hello,

What is the gate drive voltage for the power-line FET, or the voltage at SD pin?

I would like to know it in normal operation and when FET is disabled with RSD at 20kohm. And its maximum. This information is necessary for FET selection.

Thank you.

Regards,

Oguri (TIJ automotive FAE)

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DCR010505: damaged

May 23, 2019, 6:13 pm
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Part Number:DCR010505

hi sir,

 We use DCR010505 parts for generating an isolated 5V supply. We’re getting some field failures around these parts,  the failure mode  usually  appears  as  no output ，we've had  7 failure samples since last year.

one sample appears 6.6V output （it is the same as "DCR010505: damaged DC-DC converters"，which I have got at e2e  forum），but that  sample ultimately has no output voltage。

some samples are very hot. All the failure samples have abnormal output resistance ，I measured the output  resistance between  +VOUT and -VOUT with a multimeter ，value is only about 100Ω，but the good chip is about 100KΩ. I guess the internal LDO has a short circuit.

The chip is used at an Interface Circuit  for  a dry contact   status detection，  We use a cable to connect the dry contact and the PCBA board .I measured the noise on the cable，and also on the DCR's output。now the  wave is as follows:

CH1: the noise on line

CH2: the noise on DCR's output

the noise  amplitude on the DCR'is large and seems keep  sync as the line noise。 

I want to ask if this noise will cause damage to the chip？ I checked the datasheet and found no relevant instructions. 

my email is anbin.cui@united-imaging.com, we can also talk about off line.

please help me and thank you very much!

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TPS65218D0: Connection of SYS_BU

May 23, 2019, 6:26 pm
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Part Number:TPS65218D0

Dear all.

Our customer don't use IN_BU and CC.
Both input connects with GND.
Can we connect SYS_BU to GND?

Regards,
PAN-M

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BQ24725A: SI test Fail with HIDRV & LODRV pin number

May 23, 2019, 6:27 pm
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Part Number:BQ24725A

Follow as picture,I tested the U40 and U41 MOSFET G&S found that the rising and falling edges are not monotonous, please give the solution.

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LM74700-Q1: About VCAP value

May 23, 2019, 6:52 pm
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Part Number:LM74700-Q1

Hi All

My customer plan to use 1μF for VCAP..

The recommendation is 0.1 μF.
May I use 1μF ?
According to the EVM data, it is 1 μF.
What is the effect of using 1 μF on the characteristics ?

Best Regards,
Koji Hayashi
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BQ27Z561: Zero/Incorrect readings when using not enlisted Chem ID

May 23, 2019, 7:00 pm
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Part Number:BQ27Z561

Customer using EVM and BQStudio. Battery is not enlisted in the chem ID list, so they took the closest one based on voltage (4.2V)

-          Chemical ID 1202 

-          Set QMax, Design capacity, Design voltage accordingly

-          The rest as it is

-          Enabled the gauging and lifetime data collection

-          Disabled calibration mode

 

After doing so, customer is still getting zero or incorrect readings from remaining capacity, RSOC, SOH, etc. 

Is there any step that he missed out? What is the recommended method to work with batteries not listed in BQStudio?

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LMZ31710: PH connection

May 23, 2019, 7:10 pm
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Part Number:LMZ31710

Hi team,

   My customer is using LMZ31710 in below application Vin=12V, Vo=5V. We find that there is no internal connection of PH (pin10) with other PHx. And if we left all PH pin open, this will cause the output voltage to 2.7V. If we connect PH to one of PHx, the output will be 5V.

   Could you please confirm there is an internal connection of all PH pin? What problem will be if we left all PHx pin open? thanks. 

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