TPS74901: current limit vs (Vbias-Vout)

Sam Ting

Expert 3580 points

Part Number: TPS74901
Other Parts Discussed in Thread: TPS74801

Tool/software:

Hi team,

TPS74901 is a 3A LDO. Why is the current limit of the new chip less than 3A?

Regards,
Sam Ting

over 1 year ago

0 Sam Ting over 1 year ago

TI__Expert 3580 points

+ TPS74801

Can you provide a quick summary of EE difference for these two parts? That will help engineers to migrate to the new chips and understand what settings or test items are needed for evaluations. Thanks!

Regards,
Sam Ting

0 Ishaan Shetye over 1 year ago in reply to Sam Ting

TI__Genius 13670 points

We found some anomalies in the datasheet for the new device. The current limit as per Galileo is around 4.5 A. Please give us 2-3 business days to figure out the source of the anomalies and confirm the current limit. Should I send the summary of EE differences now or would you wait until next week when we have resolved the limit issue?

0 Sam Ting over 1 year ago in reply to Ishaan Shetye

TI__Expert 3580 points

Hi Ishaan,

Can you provide the summary of EE differences first and then the current limit information? Thanks!

Regards,
Sam Ting

0 Ishaan Shetye over 1 year ago in reply to Sam Ting

TI__Genius 13670 points

Specification/ Feature	TPS74801	TPS74901
V_DO (V)	60 mV typical at 1.5A, V_BIAS = 5V	120mV (typical) at 3A
Packages	VSON-10, VQFN-20	VSON, VQFN, DDPAK-7
V_{OUT, MAX} (V)	3.3	3.6
I_OUT,MAX (A)	1.5	3
V_IN,DO(New Chip)	50-100 mV @I_max	120-200 mV @I_max
V_BIAS,DO(New Chip)	1.31-1.43V @I_max	1.45 – 1.6 V @I_max
Output current limit (A)	2 - 5.5	3.8 – 5.5

This table compares key EE differences between the new chips of both devices.

0 Sam Ting over 1 year ago in reply to Ishaan Shetye

TI__Expert 3580 points

Hi Ishaan,

Sorry for the confusion! We need the differences between the new chip and the legacy chips. Thanks!

Regards,
Sam Ting

0 Ishaan Shetye over 1 year ago in reply to Sam Ting

TI__Genius 13670 points

Just to confirm, you need a comparison of the new and legacy devices for TPS74801 or TPS74901? Or both?

0 Sam Ting over 1 year ago in reply to Ishaan Shetye

TI__Expert 3580 points

Hi Ishaan,

Both, but I think datasheet EE shows the differences and find the main difference is soft start time.

From application point of view, besides SS, are there any other test items needed that you would recommend when using new chip instead of legacy for existing projects?

Thanks for your support!

Regards,
Sam Ting

+1 Ishaan Shetye over 1 year ago in reply to Sam Ting

TI__Genius 13670 points

Hi Sam,

Yes, the datasheet covers all of the EE comparison very well. Since this is a P2P replacement for the old devices, I would not recommend any other test items.

0 Sam Ting over 1 year ago in reply to Ishaan Shetye

TI__Expert 3580 points

Hi Ishaan,

Thanks! The only action item is to clarify the current limit issue with the TPS74901.

Regards,
Sam Ting

+1 Ishaan Shetye over 1 year ago in reply to Sam Ting

TI__Genius 13670 points

Per Sec 6.3.3 of the DS, "The current limit allows the device to supply surges of up to 4A and maintain regulation. The current limit responds in approximately 10µs to reduce the current during a short-circuit fault."

The DS also shows the min, nom and max values of the current limit. Please disregard the graph you had earlier referenced.

0 Sam Ting over 1 year ago in reply to Ishaan Shetye

TI__Expert 3580 points

Hi Ishaan,

Thank you for your support on this case! Let's close it. I know it takes time to update the document, but it needs to be updated to avoid confusion.

Regards,
Sam Ting

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TPS74901: current limit vs (Vbias-Vout)