with 6.6-V Input Overvoltage Protection

hello friends,

I am designing an arduino ckt with aa 3.7 li-ion back up battery.so i need a charging ckt to recharge my battery.i googled it and i selected "bq21040" by texas instruments.But in its data sheet its with 6.6-V Input Overvoltage Protection.Here i am confused, i think my 3.7 li-ion battery charged maximum 4.3v so this 6.6 v overvoltage protection is correct here.. Please help me friends by giving suggestions.if anyone know anyother charging ICs please mension here,it will be helpful for me. here i am attaching the data sheet of "bq21040".Thankyou very much

Not only the datasheet is confusing, so is your question :o What is a 'ckt' ? A circuit, schematic, chokotoff ?

The datasheet is indeed weird. They write "6.6-V" instead of "6.6 V" or "6.6V" or "6V6".
I read it the first time as "six point six minus V", and I thought is was some kind of offset.

The chip is designed to charge a single Li-ion or Lipo cell from a 5V source.
At 6.6V input voltage, the chips stops working, and at 30V input voltage, the chip gets damaged.
When knowing this, the datasheet with the numbers and graphs suddenly makes sense :wink:

I think they forgot to mention that the input voltage should be 5V :confused:

now i am totally confused :smiley:

so whats your conclusion sir? can i sue it to recharge a 3.7 v li-ion battery?

Its a phone/tablet battery charger, you can assume the input is USB for that!

Witness the beginning of the description section:

The bq21040 device is a highly integrated Li-Ion and Li-Pol linear battery charger device targeted at space-limited portable applications.
The device operates from either a USB port or AC adapter.

@ecworks, The chip is for charging a Li-ion battery from USB or other 5V source.
Do you have 5V ?

If you use for example as 12V wall wart as power supply, then you can not use this chip.

@MarkT, an AC adapter can be anything and in the datasheet they write about: "high input voltage range". I think it is a confusing datasheet.

MarkT:
Its a phone/tablet battery charger, you can assume the input is USB for that!

Witness the beginning of the description section:

ok sir.. thanks for your reply...
sir but so whats this with 6.6-V Input Overvoltage Protection?

Koepel:
@ecworks, The chip is for charging a Li-ion battery from USB or other 5V source.
Do you have 5V ?

If you use for example as 12V wall wart as power supply, then you can not use this chip.

@MarkT, an AC adapter can be anything and in the datasheet they write about: "high input voltage range". I think it is a confusing datasheet.

Koepel:
@ecworks, The chip is for charging a Li-ion battery from USB or other 5V source.
Do you have 5V ?

If you use for example as 12V wall wart as power supply, then you can not use this chip.

@MarkT, an AC adapter can be anything and in the datasheet they write about: "high input voltage range". I think it is a confusing datasheet.

ok sir thanks for your reply..i am using usb for charging and can use 5v adapter and avoid 12v adapter...
sir for my knowledge can you tell me whats really mean by this 6.6-v input over voltage protection?

If your 5V adapter would increase the voltage up to 6.6V, then the chip stops working. The 6.6V voltage protection is for the input voltage, not the battery voltage.

Koepel:
If your 5V adapter would increase the voltage up to 6.6V, then the chip stops working. The 6.6V voltage protection is for the input voltage, not the battery voltage.

Thank you very much sir for your help...
I think you are so good in English so asking you , there is any kind of automatic cut off function after full charge mentioned in its datasheet? i don't see anywhere.. and one more doubt.. in the circuit diagram the connection to TS pin of IC is From the negative terminal of the battery? is there is any temperature sensor inside the ic?
by reading the function of pin TS i think we need to connect a thermistor from battery to TS becasue i have no thermistor in my battery pack ,what you think friends? please help me , your suggestions are so valuable for me

The chip takes care of the charging up to 4.2V. They do not mention a cutoff clearly in the datasheet, but it is somewhere there. They mention for example “Recharge detection threshold”.

A battery with temperature sensor has an 10k NTC from ground to a third pin.
If your battery does not have that, then you have to limit the current to prevent that it gets hot.
The charging current is set by RISET. It depends on your battery what a safe value is. I think that 3 hours charging is too fast, and 10 hours is safe.

You can put a 15k resistor at TS. It is already in the drawing as RTS. That makes the chip think that the battery is cold.

I think there is another fail in the datasheet. The RTS resistor should not be in that drawing, if the battery NTC is used.

O no, did they fail again in the datasheet ?
The “PACK-” should be connected to ground. It is impossible that the charging current can go through the NTC. They forgot the ground symbol at “PACK-” !
Two thumbs down for Texas Instruments.
Look at the diagram on this page : http://www.ti.com/product/BQ24040
That one has the ground symbol.

Koepel:
The chip takes care of the charging up to 4.2V. They do not mention a cutoff clearly in the datasheet, but it is somewhere there. They mention for example “Recharge detection threshold”.

The maximum charge current is set by Riset selected according to data sheet figure 10. It will charge the battery at no more than that constant current until the battery terminal voltage comes up to 4.2 volts. When the terminal voltage hits 4.2 v the circuit goes into a constant voltage charging mode, holding the battery terminals at 4.2 volts until the current into the battery declines to 10% of the maximum current set by Riset at which point charging stops. This is the “termination current threshold” referred to in the data sheet.

The maximum charge current should be selected to be within the limits for the particular battery being used.

MrMark:
The maximum charge current is set by Riset selected according to data sheet figure 10. It will charge the battery at no more than that constant current until the battery terminal voltage comes up to 4.2 volts. When the terminal voltage hits 4.2 v the circuit goes into a constant voltage charging mode, holding the battery terminals at 4.2 volts until the current into the battery declines to 10% of the maximum current set by Riset at which point charging stops. This is the “termination current threshold” referred to in the data sheet.

The maximum charge current should be selected to be within the limits for the particular battery being used.

so are you saying i can use this ic with the circuit in the datasheet with out any worry? just careful to design the value of Riset? right sir?

Koepel:
The chip takes care of the charging up to 4.2V. They do not mention a cutoff clearly in the datasheet, but it is somewhere there. They mention for example “Recharge detection threshold”.

A battery with temperature sensor has an 10k NTC from ground to a third pin.
If your battery does not have that, then you have to limit the current to prevent that it gets hot.
The charging current is set by RISET. It depends on your battery what a safe value is. I think that 3 hours charging is too fast, and 10 hours is safe.

You can put a 15k resistor at TS. It is already in the drawing as RTS. That makes the chip think that the battery is cold.

I think there is another fail in the datasheet. The RTS resistor should not be in that drawing, if the battery NTC is used.

O no, did they fail again in the datasheet ?
The “PACK-” should be connected to ground. It is impossible that the charging current can go through the NTC. They forgot the ground symbol at “PACK-” !
Two thumbs down for Texas Instruments.
Look at the diagram on this page : http://www.ti.com/product/BQ24040
That one has the ground symbol.

hello Koepel,Thanks for your effort to helping me sincerely
I think they forgot to connect the PACK- to ground… i have one doubt is that if i purchase a battery without temperature sensor, then will it work if i connect an external thermistor series between battery negative terminal and TS pin of IC?

I started down the same path with a design I was working on, and then I found Adafruit Feather and decided it was a better place to start.

Feather Arduino

ecworks:
so are you saying i can use this ic with the circuit in the datasheet with out any worry? just careful to design the value of Riset? right sir?

I believe that is correct. If you are charging at a relatively slow rate (say 4 hours or more to full charge (C/4 rate)) then the thermistor protection feature probably isn’t necessary.

For what it’s worth I’ve recently been testing with a TP4056 based LiPO charger board (data sheet) and that data sheet is easier to follow than the BQ24040 data sheet. I’m not recommending one device over the other. However, since the function is essentially the same, looking at the TP4056 data sheet may clarify what pieces of the BQ24040 data sheet are relevant to your application.

MrMark:
I believe that is correct. If you are charging at a relatively slow rate (say 4 hours or more to full charge (C/4 rate)) then the thermistor protection feature probably isn't necessary.

For what it's worth I've recently been testing with a TP4056 based LiPO charger board (data sheet) and that data sheet is easier to follow than the BQ24040 data sheet. I'm not recommending one device over the other. However, since the function is essentially the same, looking at the TP4056 data sheet may clarify what pieces of the BQ24040 data sheet are relevant to your application.

thanks for your reply sir...
you are right sir.. i use a recharging module with TP4056 from ebay before.it work fine.. and now here i cannot use modules so i am looking for ics.. i read the datasheet of TP4056 its good but BQ24040 is easily available here so i selected it.
i have one doubt is that if i purchase a battery without temperature sensor, then will it work if i connect an external thermistor series between battery negative terminal and TS pin of IC?

MrMark:
I believe that is correct. If you are charging at a relatively slow rate (say 4 hours or more to full charge (C/4 rate)) then the thermistor protection feature probably isn’t necessary.

For what it’s worth I’ve recently been testing with a TP4056 based LiPO charger board (data sheet) and that data sheet is easier to follow than the BQ24040 data sheet. I’m not recommending one device over the other. However, since the function is essentially the same, looking at the TP4056 data sheet may clarify what pieces of the BQ24040 data sheet are relevant to your application.

yes sir i already used TP4056 module before,its nice one.but this time i cannot use module and as ic here BQ24040 is easily available than TP4056 ic.

sir i have one doubt is that if i purchase a battery without temperature sensor, then will it work if i connect an external thermistor series between battery negative terminal and TS pin of IC?

ecworks:
sir i have one doubt is that if i purchase a battery without temperature sensor, then will it work if i connect an external thermistor series between battery negative terminal and TS pin of IC?

Just from looking at the data sheet Koepel's prior suggestion of using a 15k Ohm fixed resistor seems as if it should work.