BQ25504: ultra low power boost converter and energy harvester

Avinash Kumar44

Part Number: BQ25504
Other Parts Discussed in Thread: TPS61256,

sir i want to drive a load which require 5V, can i use li-ion 3.7V battery at pin VBAT, will this be suitable or i need to have use battery as 5V?

over 7 years ago

0 Raheem over 7 years ago

TI__Mastermind 21590 points

Hello,
If your load requires 5V, i'll suggest you use supercapacitors in series depending on the voltage rating as your energy storage device on VBAT. During normal operation, the FET between VSTOR and VBAT is on. This means that if you set VBAT_OV to 5V you can damage your battery as most Li-ion batteries have a maximum voltage of 4.2V. You can use an appropriately rated supercapacitor on VBAT and set VBAT_OV at or above 5V depending on your requirements.

Regards,
Raheem

0 Avinash Kumar44 over 7 years ago in reply to Raheem

Prodigy 90 points

I cannot use super capacitors instead of battery because the application system is going to run for long hour without input power being available.
system is of application on IoT.
my system is promini arduino based.

0 Raheem over 7 years ago in reply to Avinash Kumar44

TI__Mastermind 21590 points

Hello,
You can add another boost converter to VSTOR to boost your output voltage to 5V because you won't be able to set VBAT_OV higher than 4.2V if you use a battery as your energy storage device. Please take a look at the TPS61256.

Regards,
Raheem

0 Avinash Kumar44 over 7 years ago in reply to Raheem

Prodigy 90 points

Hello,
i cannot use this IC as DC-DC Boost Converter ?

0 Raheem over 7 years ago in reply to Avinash Kumar44

TI__Mastermind 21590 points

Avinash,
The bq25504 is a boost converter. However, since you said that your load requires 5V and you have to use a battery, the bq25504 alone can't work. This is because you don't want to damage your battery from overcharging which is what will happen if you configure the bq25504 to output 5V. So you can configure the bq25504 to have a maximum voltage of 4.2V and then use a boost converter to boost the voltage to 5V which your load requires.

Regards,
Raheem

0 Avinash Kumar44 over 7 years ago in reply to Raheem

Prodigy 90 points

What will be the value of VRDIV voltage value?

0 Raheem over 7 years ago in reply to Avinash Kumar44

TI__Mastermind 21590 points

Hello Avinash,

The voltage value of VRDIV is shown in Figure 19 in the bq25504 datasheet and shown below.

0 Avinash Kumar44 over 7 years ago in reply to Raheem

Prodigy 90 points

I'm getting my vstor voltage 3.9 v but at VRDIV I'm getting 1.4 v why is it so ?

0 Raheem over 7 years ago in reply to Avinash Kumar44

TI__Mastermind 21590 points

Avinash,
Can you please post the scope shot of what you see on VRDIV. Also, what is your VBAT_OV set to?
Regards,
Raheem

0 Avinash Kumar44 over 7 years ago in reply to Raheem

Prodigy 90 points

My vstor is 3.5v and at pin7 VRDIV it is coming 1.1v
Why is happening I didn't get it? It should be same as vstor ?

0 Raheem over 7 years ago in reply to Avinash Kumar44

TI__Mastermind 21590 points

Avish,
Can you please post a scope shot. How are you measuring the value of VRDIV?

Regards,
Raheem

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BQ25504: ultra low power boost converter and energy harvester