TPS40304: TPS40304 upon power cycle, it does not provide full current output.

Anil Patel7

Part Number: TPS40304

When board is cool down for 4 to 5 hours and then power is apply, the TPS40304 comes up and output 10 Amp. Once it is on, It stays on for long. Upon power cycle within 1 minutes, it does not output full current 10 Amp. it output only 4.5 amp max and it shuts down.

What could cause this type of symptom? Could be a capacitor and MOSFET? or other inherent chip logic that not satisfied and shuts it down?

Thanks in advance for checking in to this post.

over 6 years ago

0 Mathew Jacob1 over 6 years ago

TI__Expert 5910 points

Anil,

Please share the schematic. Did you try raising the value of resistor for LDRV/OCP pin to ground.

Regards,
Mathew

0 Anil Patel7 over 6 years ago in reply to Mathew Jacob1

Prodigy 120 points

0 Mathew Jacob1 over 6 years ago in reply to Anil Patel7

TI__Expert 5910 points

Anil,

Was there a schematic meant to be attached in your reply?

Regards,

Mathew

0 Anil Patel7 over 6 years ago in reply to Mathew Jacob1

Prodigy 120 points

0 Mathew Jacob1 over 6 years ago in reply to Anil Patel7

TI__Expert 5910 points

Please change C92 to 0.1uF and R62 to 0hms, also change R67 to 0ohms.

Regards,
Mathew

0 Anil Patel7 over 6 years ago in reply to Mathew Jacob1

Prodigy 120 points

Why we have to change it and How do I verify that this will not affect adversely and will work consistence. Please explain what is happening on a current design? Why it is failing? I am greatly appreciate your feedback and recommendation.

0 Anil Patel7 over 6 years ago in reply to Anil Patel7

Prodigy 120 points

I have made changes per your suggestion to the board and it did not help. Any other suggestion or explanation. Please let me know.

0 Anil Patel7 over 6 years ago in reply to Anil Patel7

Prodigy 120 points

When you have mention about R77, Why not R68 change to 0 ohm?

0 Mathew Jacob1 over 6 years ago in reply to Anil Patel7

TI__Expert 5910 points

Anil,

Yes R68 can also be changed to 0ohms. What is the condition of load on power up. Is it a constant current load?

Regards,

Mathew

0 Anil Patel7 over 6 years ago in reply to Mathew Jacob1

Prodigy 120 points

Hi Mathew,

Upon start, It is suppose to output constant 10 Amp.

I have changed the resistors to 0 ohm and also capacitor to .1 uf. and no change in behavior. After the change, If I heat up, Board does not gives me 10 A. It was giving me a 10 A after heat up with all original components.

Can you call me at my cell no. 978-930-4129.

Thanks,

Anil

0 Mathew Jacob1 over 6 years ago in reply to Anil Patel7

TI__Expert 5910 points

Anil,

Sure I can call you but before that can you measure the OCP trip point with the original values. You can keep C92 as 0.1uF. For measuring OCP trip point you can check it at 25C and after you heat it up.

Regards,
Mathew

0 Anil Patel7 over 6 years ago in reply to Mathew Jacob1

Prodigy 120 points

When I try to hook up a volt meter to measure between pin 9 and ground, Some time it comes up and voltage is 1.24 V and Some time it does not and it jump between 4.5V to 0 v and dies down to 0 V. I have notice is that driver did not output 10 in past but by putting a multitier did.
once the board stay warm or I would say built up capacitance and it output 10A and stay on.
Any way give me a call and we can talk more. Hope I am making send here.

0 Mathew Jacob1 over 6 years ago in reply to Anil Patel7

TI__Expert 5910 points

Its not very clear what you are trying to convey. What is a good time for call tomorrow morning. I am in PST

Regards,
Mathew

0 Anil Patel7 over 6 years ago in reply to Mathew Jacob1

Prodigy 120 points

I am available between 12 noon to 2 PM today.

Cal me at 978-930-4129.

I am in EST (Boston).

Thanks,

0 Anil Patel7 over 6 years ago in reply to Anil Patel7

Prodigy 120 points

0 Mathew Jacob1 over 6 years ago in reply to Anil Patel7

TI__Expert 5910 points

Anil,

Values for the compensation:
R106=4640
C129=390pF
R57=215k
C78=47pF
C82=10pF

You can take the waveform at the SW pin ( one side of inductor L7) before and after the change. I need the inductor DCR and the output capacitor 820uF exact type of cap to give optimized values but the above should be good to go.

Regards,
Mathew

0 Anil Patel7 over 6 years ago in reply to Mathew Jacob1

Prodigy 120 points

L7 - Vishay IHLP5050FDER4R7M01 high current low profile inductor, smt, 4.7uH, 32A sat

C81 - C_ELEC_M82_025V Panasonic EEU-FR1E821 Electrolytic Cap 820 uF 25V thru-hole electrolytic type

0 Mathew Jacob1 over 6 years ago in reply to Anil Patel7

TI__Expert 5910 points

Okay. slight updates
R106=5600
C129=390pF
R57=178k
C78=47pF
C82=12pF

The inductor 4.7uH is very conservative in regards to ripple current ratio of 5%. You can easily change to 1uH in same series with ripple current ration of 25% and get higher efficiency. Also the same fets are used for low side and high side. I would recommend using lower Rdson fet for the low side to get higher efficiency. Vin=15V, Vo=1V means the low side is ON for 93% of the time hence the recommendation. If not for this design for new designs keep this in mind.

Regards,
Mathew

0 Anil Patel7 over 6 years ago in reply to Mathew Jacob1

Prodigy 120 points

Email has been send to you.. Please review and let me know.

Thanks

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TPS40304: TPS40304 upon power cycle, it does not provide full current output.