TPS61241: Output Current - Maximum and Short Circuit

Ryan.Bishop

Expert 3900 points

Part Number: TPS61241
Other Parts Discussed in Thread: TPS61240

Hi! I have two questions regarding the TPS61241:

1. If there is a hard short on the output, what is the expected behavior?

-How much current will the device supply?

-Will it run continuously in current limiting mode?

-Will the device only shutdown if it reaches 140C junction temperature thermal shutdown?

2. Figure 1 of the datasheet shows the maximum output current vs input voltage. At Vin=3V, the maximum output current is listed as ~300mA. However, using equation 1 on page 10 with the following parameters, I calculate an output current of 516mA. (Vin=3V, Vout=5V, L=1uH, f=3.75MHz, Ivalley=.7A)

-Which limit should I use for the design?

Thank you!

-Ryan

over 9 years ago

0 Jasper Li over 9 years ago

TI__Mastermind 46905 points

1. the device continuously limit the input current and don't switching at short circuit condition. but i need to further check the limiting value.
2. the figure is the data from TPS61240, not TPS61241. i would suggest using the minimum value 600mA, not typical 0.7A, to calculate the maximum output current.

0 Jasper Li over 9 years ago

TI__Mastermind 46905 points

the current limit value is approximately 90mA, and the device will stay at this mode if it is not thermal shutdown

0 Ryan.Bishop over 9 years ago in reply to Jasper Li

TI__Expert 3900 points

Hi Jasper,

Thank you for helping on this issue.

1. On the TPS61241, the soft start current limit is 300mA. How does the device differentiate between a short and start up in order to have different current limits?

2. To restate my question, sometimes the formula will give different max output currents than the datasheet figures. Which should I use as my design constraint?

Regards,
Ryan

0 Jasper Li over 9 years ago in reply to Ryan.Bishop

TI__Mastermind 46905 points

1. the startup of a boost converter divide into pre-charge phase and boost phase. the 300mA is the pre-charge current. the pre-charge current is related to the output voltage level. it is typical 90mA at VOUT=0 condition.
2. the figure is normally measured in the EVM. we need to use the formula to calculate the worst condition with the data in the EC table.

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TPS61241: Output Current - Maximum and Short Circuit