【BQ51013B】 Temperature Sense Resistor Network

Yamamoto-san,

I have a question about the schematic first.  It seems that R5013 is tied between OUT and RECT.  If this is accurate, this should not be done.  OUT and RECT must remain independent.  The waveforms shown indicate behavior of RECT, not of OUT.

1. 10k is recommended since it is a common value for NTC circuits. The key to the functionality of the device is the resulting voltage during the 24ms that the TS function is active (see figure 39).  Figure 37 shows a typical temperature sense circuit. Notice that R2 and VTSB are internal values and cannot change.  Choosing the appropriate NTC, R1 and R3 values must take this into account.  V_HOT and V_COLD are based on these values.

2. Best to start with an example.

V_COLD = ~ 58.7% of VTSB (0.587 * 2.2 = 1.29V)  

V_HOT = ~19.5% of VTSB (0.195 * 2.2 = 0.429V)

If I am reading the plot correctly, the voltage on the TS/CTRL pin is approximately 1.27V.  That is below the 1.29V threshold.

Other comments:

It appears that R5155 (from FOD to OUT) is not populated.  Is this correct?  There should be a resistor from FOD to RECT (R5043).  If that is in place, there should NOT be a resistor from FOD to OUT.

I do not understand R5101 to the TS node.  What is going on at the connector TS (pin 3) and GND (pin 4)?

Regards,

Dick

Dear Mr.Dick,

I answer your question and tell you additional question.

・about R5013, R5155

These two parts are not mounted. So this waveforms indicate behavior of OUT.

・additional questions

Q1 : Is it OK to apply a voltage to TS-CTRL pin directly?

You said:

>V_COLD = ~ 58.7% of VTSB (0.587 * 2.2 = 1.29V) 

>V_HOT = ~19.5% of VTSB (0.195 * 2.2 = 0.429V)

So we calculated that:

0V～0.429V             Stopping behavior（detect hot condition）

0.429V～1.29V        Working well

1.29V～        　      　 Stopping behavior（detect cold condition）

But conclusion is different:

0V～0.429V             No behavior（ERROR LED of transmitting side did not light up）

0.429V～1.29V        same as above

1.29V～        　　       same as above

*We checked stopping behavior at above voltages with changing variable rsistance on EVM board.

**In above situation, ERROR LED of transmitting side(BQ500414EVM) did not light up,

   but D8(LED_A) on EVM board dittoed 'light up for 5 sec → light out for a moment'.

Q2 : To stop charging up by main CPU, we think that appling a voltage(1.8V) or falling GND to TS-CTRL pin by force. Is it possible? To do this, we refer to datasheet P.28 '3-state circuit'.

Yamamoto-san,

I am working on a more detailed document and will post here when it's complete.

Short version is that supplying a voltage to the TS-CTRL pin does not work for emulating temperature termination.  The correct method is changing the resistance on that pin.  The EVM for the bq51013B has a variable resistor for implementing this.  The document I'm preparing shows the TS pin changing it's peak voltage as I vary the resistance.  Going higher or lower emulates the NTC (Negative Temperature Coefficient) resistor changing value as a function of temperature.  This allows an approximation of the resistance (and therefore temperature based on the NTC) of termination.

Q2.  You are correct.

Regards,

Dick

Dear Mr.Dick,

I am looking forward to hearing from you and the document you're preparing.

Additionally, I have a question about your answers to my questions Q1 and Q2.

You said that supplying a voltage to the TS-CTRL pin does not work.(at Q1)

But you said that my Q2 is correct.

I can't understand the difference between Q1 and Q2.

For example, I think that

'being pulled to 1.8V by 3-state Driver'

and

'supplying a voltage to the TS-CTRL pin'

are the same.

But you said these are different.

Please teach me these difference.

Best regards,

Yamamoto-san,

To monitor the temperature on the TS pin, the device samples the resistance.  If the pin is pulled high or low, the resistance cannot be measured and the CTRL pin functionality takes over.  Perhaps the attached PDF will assist with the explanation.

If it is not clear, Let me know.

Note that this is specific to the bq51013B and its immediately related products (bq51003, bq5105xB).

Regards,

Dick

2388.bq51013B-TS-CTRL.pdf

Dear Mr.Dick,

Thank you for your attention. But I have a question about this.

I can't understand that difference between

'TS-CTRL pin being pulled to 1.8V by 3-state Driver' and 'supplying a voltage(1.8V) to the TS-CTRL pin'.

I think that both means that the pin is pulled high(=1.8V).

So I think that the device will stop when supplying voltage directly.

Is my idea wrong?

On another matter, please teach me

the way to restart when temperature become normal temperature from OverTemperature.

I use BQ51013B's EVM(Rx) and BQ500414Q(Tx).

Power feeding is stop at OverTemperature, but don't restart power feeding when temperature become normal temperature from OverTemperature.

On the other hand, power feeding can restart after separating and getting up Rx and Tx.

Best regards,

Dear Mr.Dick,

I know you're busy, but teach me the above first question, please.

>I can't understand that difference between

>'TS-CTRL pin being pulled to 1.8V by 3-state Driver' and 'supplying a voltage(1.8V) to the TS-CTRL pin'.

>I think that both means that the pin is pulled high(=1.8V).

>So I think that the device will stop when supplying voltage directly.

>Is my idea wrong?

Best regards,

Yamamoto-san,

The TS-CTRL pin sources a current when it is measuring the resistance on the Thermistor (or 10k to ground).  If the pin is being driven by an external source, this measurement cannot happen.  So, the suggestion of a 3-state driver means that if the system is to drive the pin to force charge termination, then it must be a 3-state driver.  The external source (GPIO for example) would normally be in the high-impedance mode so the bq51xxx device can examine the resistor.

If the pin is driven high or low, with no 3-state pin, then the normal function cannot happen.

Let me know if this helps.

Regards,

Dick