BQ51021: Migration from BQ51013B to BQ51021

Mike Credelle

Part Number: BQ51021
Other Parts Discussed in Thread: BQ51013B

I am migrating a design from BQ51013B to BQ51021 because I want to enable I2C and custom packets. I am testing now and I get 5V and then after a couple seconds the circuit shuts off. Reading through the data sheet I think it is because I have a 10k resistor pull down on TS/CTRL which makes the receiver think I am in over temperature. You can see this is just a copy from the previous BQ51013B design. We don't have support for a temperature sensor in this system so can the TS/CTRL pin just be left floating? If not should I have a voltage divider from vtsb to ts/ctrl to gnd that keeps ts/ctrl at ~1V so it doesn't trip EPT or over temperature?

over 6 years ago

0 Bill Johns over 6 years ago

TI__Guru* 75756 points

Hello
For the BQ51021 Need to connect a 20k resistor between VTSB pin G4 and TS pin E5. VTSB is a 1.8V voltage source used to pull up TS. The resistor value from TS to ground in 10k.

0 Mike Credelle over 6 years ago in reply to Bill Johns

Intellectual 300 points

Can I just use another supply to get something around 1V at that TS pin, so I can confirm that the rest of the circuit works? I can't add a jumper to vtsb since it is bga part.

0 Bill Johns over 6 years ago in reply to Mike Credelle

TI__Guru* 75756 points

Yes -- Hold the TS pin above the trip point of 0.38V and 1V would work.

0 Mike Credelle over 6 years ago in reply to Bill Johns

Intellectual 300 points

I hardwired the voltage to ~.82V using a 3V3 supply that is powered by our battery. However now immediately upon connecting to the transmitter the transmitter gets a charge complete, which according to the datasheet should only happen if Vctrl>1.4V

0 Bill Johns over 6 years ago in reply to Mike Credelle

TI__Guru* 75756 points

I checked on this a little more, sorry for the confusion.
The VTSB is pulsed and TS is measured during this pulse time. The pulse is synced with communication time. The explanation in BQ51013B data sheet section 7.3.13 figure 34 gives more info. BQ5102X data sheet description is closer to DC behavior, note figure 13 shows the pulse.

This will make it difficult to test without access to VTSB pin.

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BQ51021: Migration from BQ51013B to BQ51021