SMART POWER SELECTOR OR LOAD IN PARALLEL WITH BATTERIES

FRANCISCO FERNANDEZ LINERA

Other Parts Discussed in Thread: BQ24070, BQ24030, BQ24031-Q1, BQ2005

My system has a primary power source that is a vehicle
battery voltage (12-14V typ), but I need a second power source to
supply the circuit when the primary source is not active.

I have planned to use a Li-ion (1 cell) or NiMH (3 cells) batteries as second source.

When the vehicle battery is present, It must supply the current for theLi-ion battery charge + system load current (<=200mA).

When the vehicle battery is not present, the Li-ion battery must supply the system load

I have a doubt about which topology I must use.

The first one is to put the system load in parallel with the Li-ion Battery and use a simple charger IC. At the same time that I charge the Li-ion battery , I am supplying the load. My doubt is about how the charging process of the battery (constant current - constant voltage) is affected by load current in parallel.

The second topology is to use a Smart Power selector IC (like MAX8934 for instance). So the Li-ion charge process is controlled by this IC and the load current can be supplied from the main vehicle battery when it is present and from the Li-ion battery when it is not present.

Of course, the solution must be as cheap as possible and with the minimum PCB size.

Some recommendation? TI has some circuit or application note that can help me? TI has some Smart Power Selector Circuit or similar?

Thanks in advance

over 13 years ago

0 Bryan McLaughlin over 13 years ago

TI__Expert 5055 points

Hi Francisco,

Our Battery Charge Management Selection Tool and Parametric Search make it simple to find the right battery charger for your application. For a linear charger for single-cell Li-Ion, the bq24070/1 or bq2403x families might be great choices:

BQ24070: Li-Ion Charger with Dynamic Power-Path Management, Output regulated to 4.4V
Product Folder: http://www.ti.com/product/bq24070
Data sheet (PDF): http://focus.ti.com/lit/ds/slus694f/slus694f.pdf

BQ24030: Dual Input Li-Ion Charger with Dynamic Power-Path Management, Output regulated to 6V, Vbat 4.2V
Product Folder: http://www.ti.com/product/bq24030
Data sheet (PDF): http://focus.ti.com/lit/ds/slus618h/slus618h.pdf

The parts within each family are very similar, with differences in output voltage and features. They both feature PowerPath technology, which is similar to the Smart Power Selector on the Maxim device. This allows operation and charging from the primary power source when the system is plugged in, and it will automatically switch to battery power when unplugged. If extended temperature range is required for your application, the bq24030-Q1 and bq24031-Q1 are the automotive-qualified versions.

Feel free to reply with any questions you have.

Best regards,

Bryan

0 FRANCISCO FERNANDEZ LINERA over 13 years ago in reply to Bryan McLaughlin

Prodigy 110 points

Hi Bryan,

Thank you for your quick and useful answer. Only two questions more.

Do you know the difference between G4 versions of the chip and normal (for instance, BQ24070RHLT & BQ24070HLTG4)?. I do not found the difference in the datasheet.

Are there some similar ICs solutions for NiMH Batteries?

Thank in advance

0 Tahar Allag over 13 years ago in reply to FRANCISCO FERNANDEZ LINERA

TI__Mastermind 32400 points

G4 is on the package dimensions: see tables on page 1 and 2 in the package material in the datasheet. (K0 on page 1, length, width, and height on page 2).

NIMH chargers: For single path there is bq200x

Bq2005: Switch-mode NiCd/NiMH Battery Charger for Sequential Charging Of Dual Battery Packs.

Please use our select tool on this link:

http://focus.ti.com/en/download/aap/selectiontools/battery-chargers/tool.htm

Thanks

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SMART POWER SELECTOR OR LOAD IN PARALLEL WITH BATTERIES