TPS26624-25EVM: configuration problems

user6342742

Prodigy 180 points

Part Number: TPS26624-25EVM

Hi,

I am testing the TPS26625 using development board TPS26624-25EVM, designed as below:

Target input voltage range: 4.5-27V; Input current limit: 98mA.

Here are the problems we met:

When the power supply is below 15V, the actual measured voltage value of UVLO pin and OVP pin is basically consistent with the theoretical value;

However, when the power supply is above 15V, the actual measured voltage value of UVLO pin and OVP pin differs greatly from the theoretical value.

What could be the cause of this?How should we solve it?

Looking forward to your reply, Thanks!

over 5 years ago

0 Rakesh over 5 years ago

TI__Guru** 105361 points

Hi,

Welcome to E2E!

Can you post the images again. What is the current limit of the power supply ? What is the load ?

Can you share test waveform of Vin, Vout, Input current, UVLO pin and OVP pin voltages at 15V

Best Regards, Rakesh

0 user6342742 over 5 years ago in reply to Rakesh

Prodigy 180 points

Hi,

here is the schematic and Voltage check test.

In the voltage check test, i just use the multimeter to check by now.

thanks!

0 Rakesh over 5 years ago in reply to user6342742

TI__Guru** 105361 points

Hi,

UVLO is 5V rated pin. It has internal clamp which is clamping the pin voltage. For your input range 4.5-27V, use 1M-Ohm resistor as pull-up from UVLO pin to IN and then separate resistor divider from IN to OVP to GND for setting OVP threshold

Best Regards, Rakesh

0 user6342742 over 5 years ago in reply to Rakesh

Prodigy 180 points

Hi,

Thanks for your help. According to your suggest, i changed the schematic as below.

now the OVP seems working fine.

VOUT waveform when VIN = 24V:

VOUT waveform when VIN = 30V:

Besides, There is another question i want to ask. The current limit i set is 98mA, but how can i check if it works based on the development board i got(TPS26624-25EVM).? what's your suggestion?

Thanks!

0 Rakesh over 5 years ago in reply to user6342742

TI__Guru** 105361 points

Good that helped!

After changing the current limit resistor at ILIM pin, follow the procedure in 4.4.1 Current Limit Test of EVM user's guide (https://www.ti.com/lit/ug/slvuba5/slvuba5.pdf) for evaluating the current limit behavior.

Best Regards, Rakesh

0 user6342742 over 5 years ago in reply to Rakesh

Prodigy 180 points

I set 27V overvoltage protection during the design. When the voltage exceeds 27V, the circuit is opened to form the protection, but the voltage needs to be restored to normal operation at 25V. Why? If it is the hysteresis set inside the chip, it needs to leave a certain range of protection voltage to resume work. Is it set to any value of overvoltage protection, the hysteresis voltage value is constant? What is the specific value?

0 Rakesh over 5 years ago in reply to user6342742

TI__Guru** 105361 points

Hi,

It is due to the OVP comparator hysteresis, which is 80 mv (typ)

Best Regards, Rakesh

0 user6342742 over 5 years ago in reply to Rakesh

Prodigy 180 points

I measured it is not 80mV,Why?

0 Rakesh over 5 years ago in reply to user6342742

TI__Guru** 105361 points

Hi,

How are you measuring ? can you share the data of UVLO, OVP pin voltages to look at.

Best Regards, Rakesh

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TPS26624-25EVM: configuration problems