BQ24800: About transtition of power supply AC and Battery

I'm sorry, I added the below red desription.

I would like to know about transtition of AC and Battery.
If you can, could you reply as soon, please?

1. About ACFET/RBFET OFF condition.
When AC adapter is removed, if battery voltage maximum is higher than ACDET setting,
Is ACFET/RBFET not OFF eternally?(until battery voltage goes down by self discharge etc.)
Or, charger detects the reverse current by ACN/ACP, then Charger stops ACFET/EBFET? Which is correct?

Or, does charger stops ACFET/EBFET by trriged VACN<VSRN+200mV even if ACDET is high?

Or if other behavior is correct, please teach the it, please?
We are worrying that if ACDET setting is lower than battery maximum voltage, ACFET/RBFET does not OFF when power supply is Battery only?

2. When Hybrid boost mode, if AC adapter is removed, Battery boost will be stopped by ACP/ACN current is lower than Hybrid Power Boost Mode Exit threshold (IDPM_FALL)? Is it correct?

3. Is Hybrid Power Boost Mode Exit threshold(IDPM_FALL) 93%/96% of ILIM1 set in REG0x3F()?
Or based on other REG of 93%/96%? Please teach me.

4. When Battery charging in Buck mode, if AC adapter is removed and in case that ACDET setting is lower than battery voltage, will charging not stopped?
Or will be stopped Battery charging by anything behavior?

5. When AC adapter is removed and ACDET is low then ACFET/RBFET is OFF, before ACOK condtion, Power supply is from battery via BATFET body diode?
If ACDET is low but ACOK condition is not valid, Power supply is from BATFET's body diode continue until ACOK condition is valid?

Best regards,

Thank you very much for your reply.

>1. That problem is mentioned in the datasheet. If battery boost mode is not used, ACDET must be programmed to value >higher >than the maximum battery voltage and lower than the minimum adapter voltage to work properly.

I tested by using BQ24800 EVI TI board, condition is adapter voltage 20V and Battery voltage 20V, ACDET is default of TI EVI board : about 17.5V.  

At first, pluged the  adapter voltage 20V and Battery voltage 20V by using constant voltage source, 

Then removed the adapter voltage 20V, as the result, ACOK and ACFET/RBFET was OFF immidiatly.

I think that ACOK off and ACFET/RBFET off reason is not ACDET low because the battery voltage is higher than ACDET high keeping voltage. 

(1). Based on this TI EMI board result. When do not using Battery only boost mode, even if ACDET is lower than  battery volage,  ACFET/RBFET will be turn off by removed Adapter. Is reason VACN<VSRN+200mV? or ther reason?

(2). When do not using Battery only boost mode, even if ACDET is lower than  battery volage,  is it no probem?

If it is NG, could you teach the this reason and risk, please?

[Background of question] We think that to use 20V adapter and 4 cell battery. If ACDET is set to about center of 20V and 4cell battery, It has risk that ACFET/RBFET might be OFF temporary by adapter voltage dropping by heavy load. Therefore, we would like to set to low ACDET threshold as possible.

>3. Hybrid Boost Mode exit is specified in Reg0x37[0]. It's either 93% or 96%.

What is 93% or 96% of what? ILIM1?ILIM2? or other?

Best regards,

Thank you very much for your reply.

We are thinking that  input external signal 2.43V or more to ACDET directly for keeping SPEC ACDET level to between battery max and AC minimum level when even if AC adapter voltage is dropped by high load.

Tehrefore, we would like to confirm that ACDET pin's all funtion especially functon of using ACDET pin's voltage level.  

Please teach the following.

1. About REGN LDO, 

    ACDET 0.6V or more,  REGN LDO starts. 

    ACDET less than 0.6V, REGN LDO stop. 

   Is this behavior correct? In other words, when Charger starts timing, ACDET is must be 0.6V or more?

2. When AC adapter is unplugged, ACDET changes to low no problem?

Or even if REGN LDO is started at first and then ACDET changes to low, REGN LDO will be stopped even if VCC voltage is 0.6V or more by battery?

3. ACFET/RBFET enable.

    ACDET 2.4V or more,   ACFET/RBFET on. (and ACOK)

    ACDET less than 2.4V,   ACFET/RBFET off.

    Is this behavior correct? 

4. When ACOC timing, if  input external signal 2.43V or more to ACDET directly during AC pluged, is it no problem?

   Or it has problem? If problem, please teach the reason.

5. When Inductor Short, MOSFET Short Protection timing,  even though if  input external signal 2.43V or more to ACDET directly during AC pluged, ACDET will be less than 0.6V at reject plug, is it no problem?

6. If other function uses ACDET voltage level, please teach it to me.

7. Besides, could you teach the risk and worrying points the this external circuit if you have note, please?

Best regards,

Thank you very much for your help.

(1) . Can ACDET connect to low directly when AC is removed? Or it is must be via resistor? 

       If  ACDET connecting to GND directry is NG, please teach the recommend pull down resistor and calculation method? 

(2).ACDET pin has Sink current ? or Source current?

Besidese, please teach the Sink current's value or Source current's value?(Max 2uA etc.) (Or internal pull down resistor or pull up resistor?)

(3). Could you teach the risk and worrying points the this external circuit if you have note, please?

    I left reference circuit as able to as. Besides insert the diode between ADP and circuit.

Best regards

Thank you for your reply.

>2. ACDET sinks current. It acts like a resistor to GND. The resistance could be anywhere from 100K to 1M, but keep in mind >we don't spec this parameter.

If ACDET sink current that is acted like a resistance to GND as 100kohm-1Mohm as above comment, 

R3 is pallareled with this min 100kohm, As the result, ACDET voltage will be about 1/2 by affect of the sink current as below. 

Case of there is Sink leakage of 100kohm: 

Input  20V×(133kohm×100kohm/(133kohm+100kohm)) /(866kohm+(133kohm×100kohm/(133kohm+100kohm)))= ACDET 1.237V

In other hands, Case of there is not Sink leakage:

 Input 20V×133kohm/(866kohm+133kohm)= ACDET 2.663V.

Different between there is Sink current and there is not Sink current are very big. If the sink current of 100 kohm is true, It is impossible the design even if divider is same as reference schematic. (perhaps, 100kohm sink current is not same as the actual value.)

・Therefore, Could you teach the below schematic's ACDET divider  R2 and R3 design method and the actual sink current specification for our design, please?　If you can, could you teach the it as soon as possible. I must to know the R2 and R3 desgin method by today.

Best regards,

Thank you for your reply.

>2. ACDET sinks current. It acts like a resistor to GND. The resistance could be anywhere from 100K to 1M, but keep in mind >we don't spec this parameter.

If ACDET sink current that is acted like a resistance to GND as 100kohm-1Mohm as above comment, 

R3 is pallareled with this min 100kohm, As the result, ACDET voltage will be about 1/2 by affect of the sink current as below. 

Case of there is Sink leakage of 100kohm: 

Input  20V×(133kohm×100kohm/(133kohm+100kohm)) /(866kohm+(133kohm×100kohm/(133kohm+100kohm)))= ACDET 1.237V

In other hands, Case of there is not Sink leakage:

 Input 20V×133kohm/(866kohm+133kohm)= ACDET 2.663V.

Different between there is Sink current and there is not Sink current are very big. If the sink current of 100 kohm is true, It is impossible the design even if divider is same as reference schematic. (perhaps, 100kohm sink current is not same as the actual value.)

・Therefore, Could you teach the above schematic's ACDET divider  R2 and R3 design method and the actual sink current specification for our design, please?　If you can, could you teach the it as soon as possible. I must to know the R2 and R3 desgin method by today.

・If sink current is think that as resistor to GND for design, please teach the resistor value to GND like as Min 10Mohm etc for design.

Best regards,

Thank you for your reply.　I’m sorry for added question. 

>2. ACDET sinks current. It acts like a resistor to GND. The resistance could be anywhere from 100K to 1M, but keep in mind >we don't spec this parameter.

If ACDET sink current that is acted like a resistance to GND as 100kohm-1Mohm as above comment, 

R3 is pallareled with this min 100kohm, As the result, ACDET voltage will be about 1/2 by affect of the sink current as below. 

Case of there is Sink leakage of 100kohm: 

Input  20V×(133kohm×100kohm/(133kohm+100kohm)) /(866kohm+(133kohm×100kohm/(133kohm+100kohm)))= ACDET 1.237V

In other hands, Case of there is not Sink leakage:

 Input 20V×133kohm/(866kohm+133kohm)= ACDET 2.663V.

Different between there is Sink current and there is not Sink current are very big. If the sink current of 100 kohm is true, It is impossible the design even if divider is same as reference schematic. (perhaps, 100kohm sink current is not same as the actual value.)

1. Therefore, Could you teach the above schematic's ACDET divider  R2 and R3 design method and the actual sink current specification for our design, please?　If you can, could you teach the it as soon as possible. I must to know the R2 and R3 desgin method by today.

2. If sink current is think that as resistor to GND for design, please teach the resistor value to GND like as Min 10Mohm etc for design.

3. R2 and R3 added value is around 1Mohm as reference schematic. Why the divider value is 1Mohm? Is it for saving the current consumption? Is this correct? If System is able to accept that current of ACDET divider for example around 1Mohm -> 100kohm, Is it no problem?

Best regards,

Thank you for your reply. I look forward to get your answer (1),(2).

Besides, I'm sorry for question you many times.
Could you add the below question, please? For just to make sure.

(4). Could you teach the guarantee spec of TI that the charger goes to off ACFET/RBFET, please?
Is this triger ACDET pin is less than 2.3V mim-2.4Vmax only? Is it correct?
Or other condition is necessary to the above?

Besides, if TI has the other guarantee spec that the charger turns off ACFET/RBFET, please teach it to me also.

Best reagrds,

Thank you very much for your help at difficult situation are appreciated.

Thank you for your teaching me about turn ON ACFET and RBFET timing. But I'm sorry that our question is  about timing of turn OFF  ACFET and RBFET as below. (Our question is oppside)

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(4). Could you teach the guarantee spec of TI that the charger goes to off ACFET/RBFET, please?
Is this triger ACDET pin is less than 2.3V mim-2.4Vmax only? Is it correct?

Or other condition is necessary to the above?

Besides, if TI has the other guarantee spec that the charger turns off ACFET/RBFET, please teach it to me also.

---

We must to know the above (4) within today. I'm sorry to rush you.

Best regards,

Thank you for your help. I understood the below.

-> The guarantee spec of TI that the charger goes to off ACFET/RBFET is ACDET fallling to 2.3 to 2.4 volts (typical  2.345 volts)

Best regards,

I'm sorry many times. I would like to know the official guarante specifications of TI about ACFET/RBFET OFF.
Is this the following (1) and (2) correct from pick up of your information?

(1). The only state in which ACFET/RBFET can be guaranteed to be OFF is that ACDET voltage is lower than ACDET threshold.

(2). When ACDET voltage is higher than ACDET threshold , even if VCC voltage is same or low as battery voltage, TI can't guarantee about ACFET/RBFET OFF.

Above information is very important for us.
Because we can't set the ACDET threshold between AC min and Battery max on current our system. Therefore, we will decide that countermeasure is necessary or unnecesary by using above information.

 ---------------History-------------

>Question:  When do not using Battery only boost mode, even if ACDET is lower than  battery volage,  is it no probem?

                    If it is NG, could you teach the this reason and risk, please?

>Answer:    This may work, but we don't have any information about the converter working in this scenario.

--

>Question: Could you teach the guarantee spec of TI that the charger goes to off ACFET/RBFET, please?
  Is this triger ACDET pin is less than 2.3V mim-2.4Vmax only? Is it correct?
  Or other condition is necessary to the above? Besides, if TI has the other guarantee spec that the charger turns off         ACFET/RBFET, please teach it to me also.

>Answer:  ACDET has a falling threshold of 2.3 to 2.4 volts to turn off ACFET/RBFET. The typical ACDET falling threshold is 2.345 volts.

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Best regards,

Thank you very much for your reply.

>2. If VCC is equal to or lower than the battery voltage, ACFET/RBFET will be of

Could you teach the relation the above spec and below spec that ACDET must be between AC min and Batt max, please?

My conclusion is the following from pick up your comment. Is it correct?

(1). ACDET is function to check the AC voltage is higher than Batt max. charger decides AC>Batt from ACDET and VCC -VSRN > Vlseep (around 400mV).

(2) Even if ACDET theshold is lower than actual battery voltage, if VCC is dropped same level to the battery level when depluged AC adapter, ACFET/RBFET is stopped. Until become VCC to same level to battery from timing of depluged AC, Battery discharge via BATFET's body diode, because ACDET level is lower than Battery level during this transition. At this timing, if AC line has not diode between AC adapter and ACFET/RBFET, battery discharge current fllow reverse to  the AC line because ACFET/RBFET on.

I think no problem that ACDET level is lower than Battery voltage from above (1) and (2) if battery discharge current fllow reverse to  the AC line is prevented put diode between AC adapter and ACFET/RBFET because Battery discharge flow to AC adapter is prevented by the diode. Is it correct?

Please teach that TI is able to gurantee no problem that ACDET level is lower than Battery voltage, if the battery discharge flow to AC adapter is prevented.
If not correct, please teach the detail reason of TI officail comment that ACDET must be higher than battery voltage.This is very important for us.

Best regards,

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History of your comment (from other thread: Abuot ACOK )

Qustion:Why should be set the voltage before it goes to ACDET threshold is greater than the maximum battery voltage when battery boost mode is not used?

Answer:The voltage goes around the charger like you drew. This is because when Q3 switches on ACDET is exposed to the battery voltage.

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>If ACDET is below 2.4 volts and VCC has dropped to same voltage of the battery, ACFET/RBFET is stopped.Until VCC drops to the same voltage as the >battery, the battery will discharge through BATFET's body diode. Then the battery current will discharge through the ACFET/RBFET to the AC adapter if there is not a diode between ACFET/RBFET and the AC adapter"

> Yes, that is our concern. Our concern is that the battery will discharge into the adapter in this situation.

I'm sorry. When VCC reaches the battery level, the ACFET is closed before the battery voltage becomes higher than the system side. Threfore, there is no reverse current from the battery to the AC side normally. It is perhaps no problem. We will reserch the detail continue.Thank you vey much.

Best regards,