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# TPS2595: Current limit on low voltage applications

Part Number: TPS2595

I am using the TPS259540 in several parts of one project. When input voltage is 12V everything works smoothly, I can shortcircuit or force an overcurrent on any output and the IC will behave as expected. When using lower voltages (5V or 3.3V), the current trip seems to occur but instead of turning off the output, a 300mA output remains active, with no relation to the current setting. I have tried with 1A output and 1.5A output with no difference on outcome. Using an active load I can correctly archeive 1A or 1.5A outputs, but when I go over those values the current 'resets' to 300mA and the FLT pin never triggers, no matter how hot the device gets. Again, raising Vin to +12V and trying the exact same experiment results on a correct behaviour.

I am using 1uF as input/output capacitors, 3.3nF as dVdt capacitor, 10k/12Kk as the voltage divider for UVLO, and 1.33k as Rilim.

Is there a way to solve this, or is that an expected outcome?

• Hi Pabalo,

I will get back to your query by tomorrow.

Regards,

Praveen

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• In reply to Praveen GD:

Hi Pablo,

TPS2595 has current limit operation and not Circuit breaker operation. When the device enters current limit, the output current is always held at set current limit value as long as the device does not hit thermal shutdown.

When the part is not in current limit, Input voltage is equal to output voltage. When the Part is in current limit , the Output voltage is also a function of load resistance and will be equal to minimum of VIN and ILIM x RLOAD.

VOUT = MIN(VIN, ILIM x RLOAD)

Figure 26 of datasheet shows Power Dissipation vs Thermal Shut down Time graph (data taken on EVM). This will give us an idea of how much time the device can limit current without hitting thermal shutdown and turning OFF. You can calculate Power dissipation current limit condition as product of ( VIN - VOUT) and  ILIM

It is possible that the power dissipation is low enough to keep the device in current limit mode without hitting thermal shutdown. You can measure the junction temperature of the device to confirm the same.

Regards,

Praveen

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• In reply to Praveen GD:

Hi Pablo,

Hope your question is answered. Do you have any other questions, if not can we close this thread ?

Regards,

Praveen

------------------------------------------------------------------------------------------------------------------------------

To find latest information on efuse and Hotswap, visit  www.ti.com/PowerSwitch