Battery Charger IC with Buck/Boost output

Battery Management
1

While designing a Li-Ion powered device I’m searching for a battery charger IC with two main functions:

  1. use the input power (in USB range) to either charge the Li-Ion (up to 500mA) or power the load (up to 500mA) or both (depending on the load)
  2. power to the load shall be buck/boosted to 3.3V independent from input voltage or Li-Ion voltage

The MP2632 is almost fulfilling these requests, but its output is fixed at 5V.

Is such a device available?

Thanks!

2

Hi Markus,
Thank you for utilizing MPS Technical Forum!

For that current range, a linear topology charger device is typically used. The minimum load voltage of the devices is around ~4.5V for Vsys (System/load voltage).

What is the application for your project?

Regards,
Nouman

3

Hi Nouman,
the project is a small Li-Ion powered device which communicates via a Bluetooth module. The Bluetooth module itself could work with a 3.3V LDO to limit voltage range, however, there is additional peripherial electronics which will not work correctly between 2.7V and 3.3V. An integrated buck/boost at 3.3V also would increase efficiency compared to the LDO. A separate buck/boost behind the charging IC would break with cost and space constraints.

4

Hi Markus,

SYS/load voltage for our devices are > 3.3V threshold that you need to power. Is 3.3V the max operational voltage for your application?

Thanks,
Nouman

5

Hi Nouman,
I checked all the recommended operating conditions and the overall operating range is 3.0V to 3.6V.

6

Hi Markus,
The buck boost option we have available for your application is the following:

image
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The can support higher cells, but can do with 1 cell too.

Regards,
Nouman

7

Hello Nouman,

thanks for these recommendations. I checked the datasheet of the MP2760. Do I understand it correctly, that I would have to set the minimum system voltage to 3.2V or 3.4V and to not use the NVDC functionality?

8

Hi Markus,
Looks like we do not have an option for 3.4V, the increments are shown in REG07h table of datasheet. I am not sure about 3.2V, since it will be pretty close to the 3.3V rail requirement you have. It does not leave a bit of margin.

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I would recommend using NVDC for your case since your system runs on 3.3Vs and its considered lower than Vsys.
image

Regards,
Nouman

9

Hello Noumon,
I understood the datasheet in that way, that if you enable bit 4 of Reg07h Vsys_min will be 3.2V and if you enable bit 4 and bit 0 of Reg07h Vsys_min will be 3.4V. However, both values would be allowed for all components in my system.
Using the NVDC functionality will route battery voltage to the load, as the Li-Ion battery will have up to more than 3.7V, this would be more than the allowed 3.6V maximum voltage of the components. Or do I have a wrong understanding of the NVDC functionality?

10

Hi Markus,
The BGATE driver will toggle the FET connecting pack to Vsys. Looking into MP2760 for instance. You are not wrong in your understanding.

Vsys min is the absolute minimum the device will regulate down to as the battery is depleted. However, without NVDC as the battery charges up, there is a +delta of Vtrack where Vsys will rise in parallel with Vbatt.

image

Another recommendation I have and would like you to have a look is MP2723A. It is a buck charger. However, it is possibly a better fit for your application.

Kind Regards,
Nouman