BQ24195L: System design review with BQ25195L

Prithvi Raj Narendra1

Part Number: BQ24195L
Other Parts Discussed in Thread: BQ25895

Hello,

Let's consider a system with the following supplies and loads

	Vadapter supply	5V load	Sys load	Battery supply
Voltage	5V	4.5V to 5.5V	3.5V to 4.25V	500mAh Li-Ion, 3.2V to 4.1V
Current	Max 2A continuous	100 mA max, 50 mA typical	300 mA typical, 2A peaks (GSM modem)	CC: 200 mA, CV term: 25mA
Remarks	Main supply, could turn off To Vbus pin	From Vadapter or PMID boost	From Vadapter buck (SYS) or battery supplement when Vadapter is off	Backup battery when Vadapter is absent

The questions would be

Would BQ25195L work for the Sys load described (2A peaks) considering we configure input current limit as 1.5A, system voltage limit as 3.7V ?
1. What is the transient response for sys voltage during the 2A peaks?
Can we set input current limit as 1.5A and do fast charging current as 200mA since the battery capacity itself is 500 mAh?
The 5V load needs to be powered from Vadapter when available and then from PMID when not available.
1. We can keep monitoring Vadapter and enable boost operation when Vadapter voltage falls to 0V?
2. When boost operation is on-going and Vadapter power comes back on, how would BQ25195L handle this and what should host do?
Any other aspect we are not aware of or not considering?

Thanks, Prithvi

over 2 years ago

0 Ning T over 2 years ago

TI__Guru 53391 points

Prithvi,

1. BQ24195L is a 2.5-A charger. It can handle up to 2.5A total current, i.e. the sum of the charging current and the system current. If there's charge current, the maximum system load current can be 2.5A. Please note that the charge current and the system current may also be limited by the input power depending on the input current limit setting.

Transient responses are dependent on the system design and the test conditions etc. Please feel free to evaluate the EVM based on your specific test conditions for references.

2. Please refer to note 1.

3. a. The BQ24195L has boost mode disabled by default. The host needs to enable boost mode in order to generate 5V at PMID. Please refer to FAQ at

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1023978/faq-bq25890-faq-why-does-the-pmid-pin-voltage-dip-during-vbus-removal-transient-to-the-otg-on-the-go-boost-mode-for-the-bq25890-bq25890h-bq25892-bq25895-bq25895m-bq25896-bq25898-bq25898d-bq24190-bq24192-bq24195-bq24195l-bq241

3.b. The BQ24195L is unable to detect adapter plug-in when operating in boost mode. External circuitry is needed to turn of the boost mode when an adapter plugs in.

4. Please visit https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/877725/faq-bq24192-bq2419x-schematic-review-and-pcb-layout-design-tips for BQ2419X: Schematic Review and PCB Layout Design Tips and https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/875388/faq-bq24190-bq2419x-bq2429x-faqs for BQ2419X FAQs.

Thanks,

Ning.

0 Prithvi Raj Narendra1 over 2 years ago in reply to Ning T

Intellectual 610 points

Thanks a lot Ning for the detailed responses. Few more questions not clarified in the previous posts.

I see that the min fast charging current is 500 mA. Is it possible that with we configure the input current limit as 1.5A but the battery's CC current is 200 mA?
Will there be an issue if boost is configured/enabled and Vbus is also present from Vadapter?

0 Ning T over 2 years ago in reply to Prithvi Raj Narendra1

TI__Guru 53391 points

Hi,

1. Yes.

2. Referring to 8.3.1.5 Boost Mode Operation from Battery on the d/s, one of the boost mode enable conditions is VBUS should be less than BAT+VSLEEP.

Thanks,

Ning.

0 Prithvi Raj Narendra1 over 2 years ago in reply to Ning T

Intellectual 610 points

Thanks Ning. For the two points mentioned above

For setting 200 mA as charging current how to set the registers? Because in REG02 in ICHG section the base offset is 512 mA.
So based on this you are saying that the boost operation will automatically stop when Vbus voltage comes back to say 5V?

Regards, Prithvi

0 Ning T over 2 years ago in reply to Prithvi Raj Narendra1

TI__Guru 53391 points

Prithvi,

1. REG02 ICHG range is 512mA to 2496mA. If lower than 512mA charge current is needed, please consider BQ25895.

2. The BQ24195L is unable to detect adapter plug-in when operating in boost mode. External circuitry is needed to turn off the boost mode when an adapter plugs in. For BQ25895, the device automatically exits boost mode when applying 5V at VBUS.

Thanks,

Ning.

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BQ24195L: System design review with BQ25195L