TPS61235P: TPS61235P boost converter max input current

Ashiful Khurashi1

Part Number: TPS61235P

Hello. I'm planning to use a TI TPS61235P boost converter IC for an upcoming project (VOUT 5V/3.5A with a VIN_min of 3V). In the features TI mentions there are two 10A internal power switches for the synchronous function but in the headline it's mentioned as a 8A converter, where does this descripency come from?

Also, the minimum value for I_LIM (switch valley current limit) is 6.5A. With an output of 5V at 3.5A, with a VIN of 3V the input current roughly be about (assuming 85% efficiency) 6.86A. This should work, according some of the efficiency plots I think this is doable with this IC but what is confusing me is the minimum value of I_LIM at 6.5A. Does this mean I should only draw 6.5A max at the input (since the IC can have this limit at the temperature extremes it seems)?

In short, I'm not understanding how the 10A, 8A and the 6.5A are related.

over 5 years ago

0 Zack Liu over 5 years ago

TI__Mastermind 34201 points

Hi Ashiful,

10A is the maximum current limit spec. 8A is the typical value while 6.5A is the minimum spec.

The calculation method you used is right. We need to consider the worst condition and use the 6.5A minimum current limit spec. The reason is IC switch current limit spec has variations between different units and 6.5A is the spec that TI promises.

0 Ashiful Khurashi1 over 5 years ago in reply to Zack Liu

Prodigy 70 points

Hi Zack. Thank you for the clarification.

One more question: how should I connect the EN pin? In my design the boost converter will be powered from a battery, so no digital logic signal can be used to enable the converter. In the data sheet it mentions this is a logic signal.

0 Zack Liu over 5 years ago in reply to Ashiful Khurashi1

TI__Mastermind 34201 points

Hi Ashiful,

EN logic high threshold is 1.0V. So connecting EN pin to Vin would enable the circuit.

0 Ashiful Khurashi1 over 5 years ago in reply to Zack Liu

Prodigy 70 points

Should I use a resistor to connect to VIN or directly connect it?

0 Zack Liu over 5 years ago in reply to Ashiful Khurashi1

TI__Mastermind 34201 points

Hi Ashiful,

If you have no requirement of enabling or disabling the device with a MCU, connect EN to VIN directly.

0 Ashiful Khurashi1 over 5 years ago in reply to Zack Liu

Prodigy 70 points

Hi Zack,

If I want to leave a pull-down as an option, what values should I use? I mean normally the circuit will be active, I can use a pull-up. If I want to add a disable feature, what value of pull-down should I use? I assume the resistor values will affect the quiescent current.

0 Zack Liu over 5 years ago in reply to Ashiful Khurashi1

TI__Mastermind 34201 points

Hi Ashiful,

A 1Mohm pull down resistor could be used.

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TPS61235P: TPS61235P boost converter max input current