Help identifying IC?

[iXod]

It's in a rechargeable flashlight (torch) utilizing a single 18650 Li-Ion cell. It's the only IC in the flashlight (except for the cell's dedicated protection board) so I presume it's the charge controller.

The 6-pin SMD package is labeled "57b4". That's it, no other markings or logo.

Any idea who makes it and (if I'm so lucky) a datasheet?

Thanks.

[amyk]

That's an easy one...  TP4057.

[scuzzyTerminator]

And if english is your thing...http://www.analog.com/media/en/technical-documentation/data-sheets/4057f.pdf

[iXod]

Just now getting around to working on this.

This datasheet offered shows a 5-pin device. This is a 6-pin.

Any guesses at a proper datasheet?

Thanks.

[jhpadjustable]

Hree's the product page with datasheet link: http://www.tp-asic.com/te_product_a/2009-05-20/33.chtml

Unfortunately, it's all in Chinese. Google Translate looks to be your best bet.

[Chalcogenide]

I just used the TP4057 in one of my hobby projects. I referred to the TP4056 datasheet (which can be found in English here https://dlnmh9ip6v2uc.cloudfront.net/datasheets/Prototyping/TP4056.pdf ) and just looked at the chinese TP4057 datasheet for the differences (I don't know Chinese but figures and tables were somewhat similar...). The main differences between the two devices are the lower charge current of the 4057 (500 mA vs 1A), the lack of temperature sensing and no charge enable input.

[iXod]

I’m working with an existing 4057 so the 46 (DIP8) datasheet doesn’t help me.

I am wanting to know (I’m starting to wish I could read a bit of Chinese...) if the 4057 (5-pin) is limited to 0.5A charging or if changing the PROG resistor (outside the range I think I see in the Chinese datasheet) will allow up to 1A.

Thanks.

[jhpadjustable]

I’m working with an existing 4057 so the 46 (DIP8) datasheet doesn’t help me.

I am wanting to know (I’m starting to wish I could read a bit of Chinese...) if the 4057 (5-pin) is limited to 0.5A charging or if changing the PROG resistor (outside the range I think I see in the Chinese datasheet) will allow up to 1A.

Thanks.

Ignore the Analog/Linear datasheet. It's for a different, functionally incompatible part that isn't what you want. Particularly, the LTC4057 doesn't have automatic charge termination or a status LED output, and you will severely shorten the cycle life of your battery or worse unless you manually unplug the power supply when it's done (and how would you even know for sure from outside?). The LTC4054 is a functional equivalent with automatic charge termination that you could substitute in, but you still only get about 600mA due to thermal realities and you lose the charge-complete LED because there's no pin for it.

Also, for any of these chargers, if you try to increase the charging current, you will proportionally increase the charge termination current which will stop the charger earlier. That's not necessarily a bad thing, just be aware.

The Rprog table for the TP4057 (SOT23-6) part is in the TP4057 datasheet, page 7, right-hand column.

[iXod]

One thing I see in this flashlight circuit that I don’t see in any of these datasheet is a series resistor from Vcc to pin 4 (power) of the IC. On my circuit it’s R200. None of the datasheets for the TP4057 that has pin configuration like the one I have (there are a few variations) has a R in the Vcc circuit.

What’s the purpose of this R? Why would the circuit designer choose to include it?

Thanks.
- - -
Edit:
I see in the datasheet (page attached) for the Analog LTC4057 (a different pin config and feature set) that mention is made to a Rcc resistor for the purpose of limiting charge current when temperatures get high. But the Analog datasheet recommends keeping Rcc below a couple of .

Could this the reason for the R200 in my flashlight?

Thanks.

[jhpadjustable]

Replace the R with a decimal point. It's a 200mΩ resistor. That's probably exactly why it's there: cheap insurance.

[iXod]

What is the risk of replacing Rcc with a 0 device? The 18650 has its own protection board. (The protection board wasn’t part of the original design, but came wih the higher capacity cell I upgraded to.)

[jhpadjustable]

Reduced cycle life, blown TP4057, possibly fire. The battery's protection IC is intended to protect property and life against extreme overstress events without otherwise getting in the way. Its protection likely doesn't include charging overcurrent. Look it up to be sure. The 200mΩ is intended to protect the battery's cycle life and the charger IC in regular use. Belt-and-braces.

[iXod]

Thanks JHP.

Another Q: the datasheet page discussing thermally regulated charge rate (see attached in earlier post) shows an example of how to calculate this. But Rprog isn't used in the calculation. Rprog is totally ignored here?

I'm trying to understand how the charge rate is changed from its normal value (determined by Rprog) to the thermally-regulated value (determined by Rcc). Kind of hard to do without knowing the normal Ibatt value...

Thanks.

[Yansi]

Replace the R with a decimal point. It's a 200mΩ resistor. That's probably exactly why it's there: cheap insurance.

No it is not. The input series resistor is described in the TP4056 datasheet. It is to spread the heat load on the device across multiple components.