BQ25570: Low output voltage. How to get 3.3V from the output pin?

Khairun Nisa Khamil

Part Number: BQ25570

I just bought a BQ25570 module board from 3rd party and the output is always lower than 100mV with 0.3-0.6V Vin supply from TEG. I uploaded the schematic here. I have few questions regarding BQ25570

1.I read from the datasheet and it says that the EN pin should be connected to ground to enable the IC. If you see from the schematic, Do i need to connect the EN to GND at J2?

2. I read from the thread in here that says that i need to connect Vout_EN and VBAT_OK together to turn on the BUCK operation. Is it true?

Please help. I am trying to get 3.3V at least from the output.

Thanks in advance

over 6 years ago

0 Ricardo over 6 years ago

TI__Genius 10385 points

Khairun,

To enable the IC the /EN (enable) pin must go low. If you tie VOUT_EN to GND the the buck converter will always be enabled, but this may not be desirable as the the converter may enable when the device is in cold start mode. To only enable the buck converter when the device is out of cold start, you must tie VOUT_EN to VBAT_OK.

Thanks,

Ricardo

0 Khairun Nisa Khamil over 6 years ago in reply to Ricardo

Prodigy 40 points

Is that mean i just connect the EN to GND and Vout_EN pin to Vbat_ok from the right away? or I need to wait it to reach the cold start?

0 Ricardo over 6 years ago in reply to Khairun Nisa Khamil

TI__Genius 10385 points

Khairun,

Yes. Connect /EN to GND to enable the chip. Connect VOUT_EN to VBAT_OK. You will have to wait until the device is out of cold start to see the 3.3 V output on VOUT. This time will vary depending on VIN.

Thanks,

Ricardo

0 Khairun Nisa Khamil over 6 years ago in reply to Ricardo

Prodigy 40 points

Thanks Ricardo! Got it.

1 last question. But if i want the output to be 5V just connect /EN to GND only right?

0 Ricardo over 6 years ago in reply to Khairun Nisa Khamil

TI__Genius 10385 points

Khairun,

To get 5V on VOUT, you will have enable the IC by connecting /EN to GND and VOUT_EN to VBAT_OK. You will have to adjust your resistor network accordingly to set VOUT to 5V. Please note that the output of VOUT comes from an internal buck converter fed from VSTOR. This means that your VSTOR must be greater than VOUT. The electrical characteristics table in section 6.6 of the datasheet says that VOUT must be greater than VSTOR by 200mV.

Thanks,

Ricardo

0 Khairun Nisa Khamil over 6 years ago in reply to Ricardo

Prodigy 40 points

Understood!! Thanks Ricardo!

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BQ25570: Low output voltage. How to get 3.3V from the output pin?