BQ21080: NCT range and reference design

Hi Francisco,

It's important to keep the TS/MR voltage range in between your programmed TS thresholds so at most your TS HOT and TS COLD thresholds. Based on that, I do have a concern with your 100k pullup to 1.8V and capacitor on the TS/MR pin. Is there an intended purpose for it? This is a current based TS charger and so there is no required voltage pullup; only an NTC is required along with your pushbutton. For an NTC we recommend a 103AT-2 10k NTC. 

The BQ25180EVM would be the same. If you'd like to try the BQ21080 it's recommended to take a BQ25180EVM and replace the IC at the moment. For the BQ29801, you'll need to create a different thread regarding that.

Best Regards,

Anthony Pham

Hello Anthony, 

Thank you so much for your feedback. The goal of the 100k Resistor is to have extra control by the uC. I would like to have the option with the push button and by the uC. So, do you recommend changing the IC? or just for the reference design? 

What about the BQ27427? would be needed another ticket?

Thanks!

Francisco

Another thing, the NTC is a through hole component, don't you have an SMD one?

Regards

Francisco

HI Francisco,

This will still interfere with the TS portion of the operation as it may see 1.8 V which is outside of the valid charging range. 

If you desire using a an MCU to also do push button activities, it is recommend to do this by driving a FET to pull TS/MR down in parallel to the NTC and push button. 

Here is a link to many SMD thermistor components with the same beta value: 10 kOhms SMD/SMT 1 % NTC Thermistors – Mouser

Best Regards,

Anthony Pham

Hi Anthony, 

So, do you mean that could be possible to add only the CHN mosfet in parallel without any pull up? I am guessing that should be internal. On the other hand,, do you recommend using the BQ25180?

Regards

Francisco

Hi Anthony,

Do you know somebody that could help with the complete connection? I would like to make sure that the all power section is correct.

Regards

Francisco

Hi Anthony,

Do you know somebody that could help with the complete connection? I would like to make sure that the all power section is correct.

Regards

Francisco

Hi Francisco,

Yes, I am saying you cannot directly connect the TS/MR pin to a logic voltage. The TS/MR push button functionalities are active LOW. Something like this is intended. 

The BQ25180 is one of our newest devices and incorporates our 1-A power path chargers with ship mode and shutdown mode -- our lowest current consuming modes in our linear 1-A portfolio. It's highly configurable and so you can do a lot of creative things with it in regards to charging. 

Best Regards,

Anthony Pham

I am only an expert for the BQ25180. I can forward this thread to relevant engineers once we are done here. If you are ok with the circuit I shared in the thread I can pass it along.

Best Regards,

Anthony Pham

Hi Anthony, 

Thanks for you feedback. This is the final version

If you agree, let's keep forward sharing the design with your partners. 

Thanks

Francisco

Hi Francisco,

That looks better but the capacitor on the TS/MR pin is also not needed. If you are using an NTC on the Fuel Gauge, please replace the capacitor with a 10k resistor. Do note that you will not have any Battery Temperature Sensing from the BQ25180 unless you have an NTC on the TS/MR pin. If you have one on the Fuel Gauge, you will need to configure software if JEITA for battery charging is desired.

For the rest of the BQ25180 portion of the schematic, I did notice one additional item. The C1 capacitor needs to be at least 1uF. You currently have 100nF. 

I can pass on once these are changed.

Best Regards,

Anthony Pham

Hi Anthony,

Thanks for your feedback.

Ok, I was considering do not add the NTC, but I will. In case of the capacitor, it is on other side of the complete schematic, this section is only the battery management section. 

My main concern is the interconnection between the other ICs. I would like to make 100% sure that the interconnection is correctly done.

Regards

Francisco

Just FYI, I have a 10uF and 1uF caps at VDDIN

Hi Francisco,

This capacitor is on the other side of the schematic? Do you mean the PCB?

My concern is that it will be charged eventually if the push button is pressed or the N-Channel FET isn't turned on and that it may not charge fast enough for the voltage to be in the valid range of charging.  Is there an intended purpose for the capacitor?

Francisco Zamudio said:

Ok, I was considering do not add the NTC, but I will

This is not required. I had misread the part on the fuel gauge and thought it had a pin used for NTC. That's an apology on my part. You can use a 10k resistor here as I mentioned previously but my main concern is the 100nF capacitor. 

If you'd like to not have a resistor there, you can disable the TS_AUTO function but I cannot guarantee push button functionality with a capacitor present as this is outside the operation described in the datasheet. 

Best Regards,

Anthony Pham

Hi Anthony

I was talking about the C1 which is on the power pin, so, I have other caps in parallel with the C1 in another section of the schematic. The C? is the cap that I would replace with the NTC.

I going to use the NTC. 

Regards

Francisco

Hi Francisco,

I've been told by the gauge team that the gauge portion looks fine. Waiting on someone from the battery protector team. 

Best Regards,

Anthony Pham

Hello Luis!

Thank you so much for your feedback. The plan is not to go so low. 

On the other hand, I've used these MOS transistors, could you please confirm if those are a good option?

rocelec.widen.net/.../FAIR-S-A0000571472-1.pdf

Regards

Francisco

Thank you so much, Anthony, just have a final question, Could you please confirm if the 1.8V to I2C and int are ok?

Regards

Francisco

Hello Luis, Thank you so much for your feedback. One last thing, I've seen in the EVM that the GND is connected to the battery side of all GND connections. So, should be like that? 

This is my current configuration The GND connection is after the small resistor.

Regards

Francisco

Just to clarify, I've been talking about the GNDBatt (for reference on my schematic) for the connection of all devices on the BQ2980. My understanding is that the GND for the system would be my GND but the EVM schematic and the reference in the datasheet make me feel confused. Could you please clarify the Ground connection? 

Regards

Francisco