TPS40055: SS current source

K.Yaita

Part Number: TPS40055

Hi Team,

I believe UVLO circuit holds SS pin low until the input voltage exceeds the user-programmable undervoltage threshold when powering-up TPS40055.
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1)
Is there any way to see enable timing of SS current source other than monitoring VIN?
Is it same timing with BP5/BP10 starts to output?

2)
Is there any way to judge SS current source is enabled or disabled?
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The background of the question is one of my customer's boards shows SS pin holds low even if VIN is applied, so would like to ask above questions.

Best Regards,
Yaita / Japan disty

over 7 years ago

0 Samuel Jaffe over 7 years ago

TI__Mastermind 25590 points

Yaita-san,

1. You can monitor SS voltage to see when it starts to charge. BP5 and BP10 should rise directly with VIN. SS should start rising at the same time unless the IC is in a condition that pulls SS low, like current limit or UVLO.

2. To see that SS current source is enabled, monitor SS voltage. If you need to monitor the current at all times, you can add a resistor in parallel with the soft start cap to ensure there is current flowing out of the SS pin.

-Sam

0 K.Yaita over 7 years ago in reply to Samuel Jaffe

Guru 29720 points

Hi Samuel-san,

Thank you for your kind support.
Do you know which reference voltage (red part) is power supply of SS current source?

Best Regards,
Yaita

0 Samuel Jaffe over 7 years ago in reply to K.Yaita

TI__Mastermind 25590 points

Yaita-san,

See the EC table on the datasheet. SS clamps at 3.7V. SS uses the 3.5V regulator.

-Sam

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TPS40055: SS current source