UCC28950: PWM temporarily stop output when output short circuit testing

May 21, 2019, 7:44 am

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Part Number:UCC28950

Hi team,

Customer facing a problem when doing output short circuit testing on UCC28950.

As first waveform shown below, once short-circuit happen, output voltage drop immediately and UCC28950 stop output.

In the second waveform, it shows VREF and SS are both stable and SS not fall below 3.6V.

In the third waveform, you can find the CS/EN pin does not exceed current limit threshold 2V.

In last waveform, we verify the PWM output of UCC28950 stops. 

Please help to provide your comment on why this phenomena happen and suggest us to improve this situation. Thank you.  

-----------------Waveform investigation-------------------

Green line: VOUT, normal is 54V

Blue/Purple Line: VDS voltage of MOSFET-A/B which is driven by UCC28950 OUT-A/B

Light blue Line: Transformer Input current which is driven by full bridge

Green line: VREF voltage

Blue Line: VOUT, normal is 54V

Purple Line: SS pin voltage

Light blue Line: Transformer Input current which is driven by full bridge

Blue Line: VOUT, normal is 54V

Green line: CS/EN 

Purple Line: EA+ which is from Vout sensing feedback

Light blue Line: Transformer Input current which is driven by full bridge

Green Line: VOUT, normal is 54V

Purple Line: Vgs waveform which is driven by OUT-A

Light blue Line: UCC28950 OUT-A 

Regards,

Alex

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TPS7A8101: Does it make the ripple worse in case of Vin=5V,Vout=5V

May 21, 2019, 7:47 am

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Part Number:TPS7A8101

Dear all：

      I'm evaluating TPS7A8101，Does it make the ripple worse in case of Vin=5V,Vout=5V？

Our demand is the normal 5V power supply. We need to get a low-noise 5V power supply. The current demand is 1A.If there is a suitable device, please help to recommend it

Thank you！

• I'm evaluating TPS7A8101

TPS1H200A-Q1: With Lithium-Ion Battery - charging and discharging

May 21, 2019, 7:55 am

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Part Number:TPS1H200A-Q1

Hi,

My design uses a 14.4V nominal (16.4V max) 2000mAh Lithium-Ion battery. I am using the TPS1H200A-Q1 to limit the inrush current drawn by the load connected to this battery.

The IN & VS pins are connected to the positive terminal of the battery and the OUT pin is connected to the system load via a Lithium Ion charge controller (MAX1873T). This configuration is intended to limit the current drawn from the battery (battery discharge current) to a value that has been set using R(CL) on the TPS1H200A.

However, when my system is powered using an external 24V DC supply, the Lithium Ion charge controller is designed to charge the battery with a charge current of 1A. This current would flow in the reverse direction through the TPS1H200A. Is it okay to have this charging current (which would be reverse current for the TPS1H200A) flow continuously through the body diode of the TPS1H200A ?

Also, the Lithium charge controller is designed to charge the battery to a voltage to 16.4V. Would it be valid to assume that since the charging current tapers down to zero as the battery approaches full charge, that the drop across the body diode will be negligible when the battery is fully charged. Will the battery get charged to the desired value of 16.4V if the charging current flows in reverse direction through the TPS1H200A?

TPS54360: TPS54360 Production damage problem

May 21, 2019, 8:09 am

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Part Number:TPS54360

Hi Ti team,   

1. Phenomenon: TPS54360 is burnt out in the aging process(Vin=30V,Vout=5V/0.2A-2A) and abnormal impedance was found in Vin, Sw or EN pin

The Vin pin in particular has burned off. About 5pcs out of 100pcs were burnt out

2. Check and test found two problems:

A, IC BucK circuit is not stable, and the waveform of Sw foot is different in size (as shown below)

.

B. Input 30V  start up, Vout 5V/ 1.5a or above current test start up waveform, Vout overshoot up to 8.3v

3. Rectification results:

A, FB feedback the capacitance in parallel on the pull-up resistor, C95 0.1uf is removed, and the problem of abnormal waveform of SW foot is improved( test waveform as below)

B. The working frequency of the switch is changed from 1Mhz to about 700K, which improves the overshooting problem of output voltage

4, After modification, Producted 100PCS for aging experiments(Vin=30V,Vout=5V/0.2A-2A), and now another one is found burnt out, the phenomenon is the same as before

5,Please help to confirm whether there may be other problems causing such burning?

6, SCH as below

LM3534 (LED backlight driver) data sheet

May 21, 2019, 8:15 am

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Hi Team,

I'm posting this on behalf of our customer.
Can you share if you still have available data sheet for this obsolete TI part since it is not searchable anymore in the TI website:
LM3534: LED backlight driver

Thanks!

Jonathan

BQ34Z100-G1: GPC report warning

May 21, 2019, 8:22 am

≫ Next: LM5143-Q1: Behavior of VDDA when EN1=EN2=0V

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Part Number:BQ34Z100-G1

Dear All:

   I have done lots of  the GPCRA0 report without any problems, but this time except the following problems

   I  upload the  learning cycle log files  in the GPCRA0  web tools. but the email reply the report as below attachment.

 "Warning: Voltage under load 4201 mV is higher than OCV 4185mV. Please check correctness of your chem ID."

  the attachment is the  Chem id log files and learning cycle log files. can you help tell me what's wrong in my  process? Thanks~

 (Please visit the site to view this file)(Please visit the site to view this file)(Please visit the site to view this file)(Please visit the site to view this file)

LM5143-Q1: Behavior of VDDA when EN1=EN2=0V

May 21, 2019, 8:48 am

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Part Number:LM5143-Q1

What is the behavior of VDDA on the LM5143-Q1 when EN1=EN2=0V?

Does it remain enabled, independent of EN1 and EN2?  I assume yes, but wanted to confirm.

From what I can read in the datasheet, given that VDDA is used to configure the device, I am assuming it is enabled upon VCC being at a certain level and is only controlled by VCC itself.

What are the circumstances of VDDA being turned off?

BQ2002 NiMH charging circuit not delivering enough current

May 21, 2019, 9:02 am

≫ Next: TPS50601A-SP: Fly-Buck or Fly-Buck-Boost Topology

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I have the following schematic for a NiMH battery charger which will get charged through a USB 5V input.

I am charging 2 1.2V cells each rated at 1.2V.

When the circuit is running I noticed that the TIP32C does not get hot at all. Is this supposed to happen?

There is an output current of 330 mA, I need at least 550 mA. What do I need to change in the circuit?

Below is the schematic:

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TPS50601A-SP: Fly-Buck or Fly-Buck-Boost Topology

May 21, 2019, 9:48 am

≫ Next: TPS61089: VQFN package and SOT package

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Part Number:TPS50601A-SP

Hi,

I'm wondering if the TPS50601A-SP can be configured to support a Fly-buck or Fly-buck-boost topology.

Thanks!

Luis Martinez-Mitjans

TPS61089: VQFN package and SOT package

May 21, 2019, 10:04 am

≫ Next: TPS92691: Can TPS92692 be configured with a low side current sense resistor?

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Part Number:TPS61089

Hi  All,

Long chat with ti export I have selected IC TPS61089 for my commercial project.  But at the design stage i found that IC manufactured VQFN package only . Hence can you please advice me about SOT package that have similar specification to  TPS61089 

Thanks in advanced 

TPS92691: Can TPS92692 be configured with a low side current sense resistor?

May 21, 2019, 10:43 am

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Part Number:TPS92691

Can TPS92692 be configured with a low side current sense resistor?

TPS61089EVM-742: Vout droop under load

May 21, 2019, 10:58 am

≫ Next: BQ24195: Charging a Supercap as a Li-Ion

≪ Previous: TPS92691: Can TPS92692 be configured with a low side current sense resistor?

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Part Number:TPS61089EVM-742

I have a TPS61089EVM connected to an existing board to boost a LiPo battery to a higher voltage for driving speakers. The six 8Ω speakers used in the design are driven by half bridges controlled using PWM signals. For testing I'm using a bench power supply rather than a LiPo battery. The output of the TPS61089 is connected to the VHAP supply net shown in the schematic snippet below:

If I drive all six speakers with the same wavetable, I encounter occasional dips in the output of the TPS61089EVM output. The R1-R3 resistors have been reworked for 6.1V output, but otherwise remain unchanged (current limit, switch frequency, etc). Oscilloscope captures are below, with yellow representing the TPS61089 output and fuschia representing the bench supply input:

Waveform playback without Vout 'dips':

Waveform playback with Vout 'dips':

I measured the input supply current peaks at around 1.1A, well below the TPS61089EVM's default 8.1A current limit and the bench supply's 3A current limit, and don't observe sizable dips in the input supply voltage. What is the cause of these dips, and what can I do to prevent them?

BQ24195: Charging a Supercap as a Li-Ion

May 21, 2019, 11:06 am

≫ Next: TPS2832: High-level input voltages on the IN and DT terminals must be less than or equal to VCC.

≪ Previous: TPS61089EVM-742: Vout droop under load

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Part Number:BQ24195

Battery Charger team,

Our customer has designed a battery charge circuit based on the bq24195 for Li-Ion.  In some of their applications, they want to change to use a 2S Super-Cap.  I know we have the devices specifically designed for Super-Cap, but can you tell me if it's possible to use this charger to charge a Super-Cap, configured to charge with a Li-Ion profile?

Are there concerns, or is it simply that it will take longer to charge than with something like a bq24130?

If it won't work, can you explain why?

Thanks,
Darren

TPS2832: High-level input voltages on the IN and DT terminals must be less than or equal to VCC.

May 21, 2019, 12:25 pm

≫ Next: BQ24650EVM-639: BQ24650EVM-639:

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Part Number:TPS2832

Data sheet for TPS2832 states:  "High-level input voltages on the IN and DT terminals must be less than or equal to VCC."

Our configuration uses this part where DT is slightly higher then VCC (or can be).  Is this requirement there because there is diode protection between IN, DT and Vcc pins?   Can I put schottky diode across DT and VCC for protection? 

BQ24650EVM-639: BQ24650EVM-639:

May 21, 2019, 2:14 pm

≫ Next: TPS543B20: Bootstrap capacitor voltage rating

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Part Number:BQ24650EVM-639

Hi there,

I have been running the BQ24650EVM as it was shipped with Vout, as per equation 1 on page 3 of SLUU444A , set to 12.6 volts with R13 and R15 being 499k and 10K respectively.  As well, the sense resistor, R6 is 20m Ohms.

I was testing out the EVM unit with a 12 volt, 8 Ah lead/acid battery with max recommended bulk charge rate of 2A.  (It was my intention to later modify this circuit as per the document SLVA437A for a lead acid type battery which we are designing for but for now,  I just wanted to do a ‘sanity’ test.

When connected to a 21 V ( 4 amp current limit) supply, the EVM drew 193mA which translated to a current going into the battery of 280mA. The battery voltage  at the start was 12.45.

The final readings just before the charge current shut off and the Stat 2 LED turned on where the following….

Input current 135Ma  ,  Battery charge current 188.5mA     Battery Voltage   12.48 V

My questions are:

1) What can I attribute the error to regarding how early it shut down. I understand that the lead acid full charge would be more between 12.8 to 13 .2 volts not to mentioned that a float charge is missing, but given the values used on the EVM board for the sense resistor and the two resistors that make up the voltage divider , I would have expected to get closer to the assigned value of 12.6 Volts. Why did the current get so low before it turned off ? I had measured the voltage across the sense resistor and it was measuring 3 mV while it was still charging. The charge termination voltage (Vtermchg) on page 6 of the data sheet has the threshold as being 4mV.

2) We won’t be using it in our final design but how does one tell if a Li Ion battery is in the pre-charge state or in the bulk state of charge ? Is this apparent from the Status outputs?   They are mentioned on page 13 of the data sheet in 8.3.4 but this is not necessarily a fault condition provided   is gone within 30 minutes - correct ? 

3) The data sheet on page 12 equation 1 uses the term Vbat (or Vout if you refer to equation 1 on the SLUU444A EVM guide page 3) Do these expressions represent what voltage will always be applied to the battery terminals or do they represent how high the voltage on the terminal must get before the current shuts down. This is confusing because as I referenced earlier, I thought the shunt resistor was determining at what point to shut down the current.  Maybe I'm getting my constant voltage and constant current terms mixed up ?

Regards
Dave

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TPS543B20: Bootstrap capacitor voltage rating

May 21, 2019, 3:38 pm

≫ Next: BQ27541-V200: Questions about the Hibernation mode in BQ27541-V200

≪ Previous: BQ24650EVM-639: BQ24650EVM-639:

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Part Number:TPS543B20

Hi

The datasheet states that the bootstrap capacitor should be rated at 25 V or higher. The "BOOT to SW" parameter is max 6 V so is a voltage rating of 25 V really necessary?

My input voltage is 9-15 V and the output voltage is 0.85 V.

Regards, Jonas

BQ27541-V200: Questions about the Hibernation mode in BQ27541-V200

May 21, 2019, 3:38 pm

≫ Next: TPS65563A: Adjusting output voltage

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Part Number:BQ27541-V200

Hi,

Customer has some critical questions for the hibernation mode in BQ27451-V200. Could you help to check and give some comments?  

Thanks a lot.

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

I understand 

a: we need to setup [Hibernate] to 1 to exit from “Sleep” into "Wait_Hibernate". (We should follow TI instruction already and available to read out indicate from GUI control console, which means status set right through I2C).

b: then Average current()< Hibernate current or Vcell<Hibernate voltage, to exit from "Wait_Hibernate" into Hibernate mode. This is the point I need further brief. 

• Question： What's the Average current sample period. Few seconds( 20 Seconds from above table) or minutes? I recall during former TI FAE discussion, he high light there's time delay to secure fully enter into Hibernation mode

 

c: Let's say If battery pack has enter "Wait_Hibernate" mode but fail to enter "Hibernate" due other reasons like I2C noise or Averagecurrent() take long time to below hibernate current? Which state will be back? Sleep Mode or WaitFullsleep mode？ What Level of quiescent current should I expected 

 

 

d: we also understand BQ27451 will exit from Hibernate mode if there's communication activity on I2C and -V200 are very sensitive to I2C noise from TI FAE and below upgrade applied to -G1 version(slua641a).

• Question: What's the software filter threshold value here to ignore the I2C noise, few seconds or minutes?

TPS65563A: Adjusting output voltage

May 21, 2019, 4:20 pm

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Part Number:TPS65563A

I was wondering if there is a recommended way to adjust the output voltage? I would like to charge to 200V, not 300V, and am driving an ultrasonic transducer. I can't just use time because the load doesn't reduce the output voltage to 0 V after a transmission. Is monitoring the output voltage using a resistor divider and A/D the best solution?

TPS61099: Fixed voltage output FB pin internal connection.

May 21, 2019, 4:29 pm

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Part Number:TPS61099

In the data sheet it says to connect the FB pin to ground for the fixed output voltage versions of the TPS61099, I can't tell from the block diagram whether it is connected internally to ground or if it is connected to the ground output for the resistor divider or no connection at all. I am asking because I have ordered some PCBs with the FB pin left floating accidentally and I was wondering whether I should cancel the order if it the chip will not work without this connection.

WEBENCH® Tools/TPS23753A: TPS23753A issue

May 21, 2019, 4:33 pm

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Part Number:TPS23753A

Tool/software: WEBENCH® Design Tools

Attached is the schematic diagram of TPS23753A drawn by our company. The isolation transformer USES coilcraft poe13p-12l.Pls help to check.thx.(Please visit the site to view this file)(Please visit the site to view this file)