Reg output current issue in TPS70933

Aravind .R

Other Parts Discussed in Thread: LM317, TPS62177

Hi All,

I have suggested TPS7A4533 to one of the customer in the datasheet it is mentioned quiescent current is 1microamps but it is taking 100microamps so i suggested TPS70933 . In TPS70933 the leakage current is matching as per the datasheet but although it is rated as 150mA o/p current not able to pull more than 50mA. Beyound 50mA ouput is toggling and chip is getting heated up. Attached is the output waveform at 80mA for your reference. Kindly help to resolve or help to suggest a right part matching the specs equivalent to TPS70933. kindly need help.

Regards,

Aravind

over 10 years ago

0 Aaron Paxton over 10 years ago

TI__Expert 5565 points

Aravind, This looks like thermal shutdown. What's the input voltage? Also, which package are you using? - Aaron

0 Jamshid Kakkattil over 10 years ago in reply to Aaron Paxton

Prodigy 60 points

Dear Aaron,

We have tried the input with 18V 3Ah -Li Ion Battery.

0 Aaron Paxton over 10 years ago in reply to Jamshid Kakkattil

TI__Expert 5565 points

Jamshid,

That's quite a large input-output differential. Dissipation is found by the following: (Vin - Vout) x Iout. There's too much heat being dissipated. You'll either need to use an LDO with better thermal characteristics or a buck converter to avoid going into thermal shutdown.

- Aaron

0 Jamshid Kakkattil over 10 years ago in reply to Aaron Paxton

Prodigy 60 points

Aron,

Can you please suggest me an equivalent part with better thermal characteristics.

Required output current is 100mA at 3.3V from an 18V battery and with shutdown pin.

0 Ryan Eslinger over 10 years ago in reply to Jamshid Kakkattil

TI__Guru 55940 points

Hi Jamshid,

There are a couple of options due to the large input to output delta. You could put a DCDC in series before an LDO or even cascade LDOs. Depending on your ambient temperature, LM317 may work for your application.

Very Respectfully,

Ryan

0 Aravind .R over 10 years ago in reply to Ryan Eslinger

Genius 3175 points

Dear Ryan/Aron,

Further to above discussion i suggested TPS62177 buck converter for the customer to look into as thermal shutdown problem they are facing in LDO. They are ok with this part. Is there any better buck converter that can be suggested for below specifications at a low cost. please suggest a part with very low quiescent current as it is battery operated device and battery voltage will be 18V. Else LDO matching the below specs with good thermal characteristics with very low quiescent current is also ok to look into. Kindly need your reply.

Input voltage : 2-30V

Output voltage : 3.3V fixed

Output current: 150mA

0 Ryan Eslinger over 10 years ago in reply to Aravind .R

TI__Guru 55940 points

Hi Aravind,

For the best recommendation on a buck converter, please use the non-isolated DC/DC forum. This forum is monitored by people more familiar with the buck converters than I am.

Very Respectfully,
Ryan

0 Aravind .R over 10 years ago in reply to Ryan Eslinger

Genius 3175 points

Dear Ryan,
Thanks. Is it possible to move the complete set of above discussions to non -isolated DC/DC forum so that they will go thru and revert back.

Regards,
Aravind

0 Ryan Eslinger over 10 years ago in reply to Aravind .R

TI__Guru 55940 points

Hi Aravind,

Good idea. I will move this thread for you.

Very Respectfully,
Ryan

0 Chris Glaser over 10 years ago in reply to Aravind .R

TI__Guru**** 150830 points

Yes, the TPS62177 is the lowest Iq buck that can operate in your region. Note that any buck or LDO requires Vin to be greater than Vout for Vout to be in regulation. So, your minimum Vin will be somewhere above Vout. For the TPS62177, you can operate it down to 4.75Vin.

0 Aravind .R over 10 years ago in reply to Chris Glaser

Genius 3175 points

Dear Chris,
Thanks for your valuable reply. But battery voltage tey have used here is 18V one.

Regards,
Aravind.

0 JohnTucker over 10 years ago in reply to Aravind .R

TI__Guru**** 191445 points

The TPS62177 will operate with your input voltage of 18V, the input voltage range is 4.5V to 28V. In a previous post you mentioned a range of 2V to 30V. Can you confirm this? If you really need to operate down to 2V input it will require a buck boost.

0 Aravind .R over 10 years ago in reply to JohnTucker

Genius 3175 points

Hi,

No i don't need that kind of low voltage to operate. I have mentioned it as 2 to 30V and this 4.5 to 30V is enough and customer is also ok with it.

Thanks for all of your suggestions.

Regards,

Aravind.

0 Jamshid Kakkattil over 10 years ago in reply to Chris Glaser

Prodigy 60 points

Hi Aron/Aravind,

I tried the Buck Convertor, But the Iq id found little bit high. It takes about 4.2uA when EN=0 which is not allowed in my design.

0 Aravind .R over 10 years ago in reply to Jamshid Kakkattil

Genius 3175 points

Hi Aron,

customer tested with TPS70933 & it is getting damaged continuously. please need your help to resolve this issue, all technical details & schematics are attached for your reference. kindly advise.

Disable Mode Leakage Current: About 1uA

Working Current: About 30 mA

Working: The Ckt will pull down the ENABLE pin of regulator always to ground through a 10K resistor and that time the leakage current is about 1uA.

When the switch J1 (Push Button)is closed manually, a higher voltage of about 2V comes at ENABLE Pin (Through R1,R3 Resistance Network)which enables the U8(TPS70933) and 3.3 Volt VCC is generated.

This will power up the microcontroller and will take the control of Enable pin through PWR_CRL_MAIN.

The Other Part,R4,R13 is connected to M10 which will turn on the MOSFET on the button press(J1), which is used to pull down the CRIMP_SWITCH Line which is used as a microcontroller Interrupt.

Rgds,