# Understanding AMC7135

#### Tedfs

##### Newly Enlightened
Please forgive my lack of understanding as I try to learn.

What exactly is the function of the AMC7135 that is tossed around so frequently ?
I know that 8 of them will run an XML on 2 primary CR123s but 4 of them will not. I just don't understand the role/function the AMC7135.
What exactly is it doing to control what gets to the emitter ?

#### DellSuperman

##### Flashlight Enthusiast
Please forgive my lack of understanding as I try to learn.

What exactly is the function of the AMC7135 that is tossed around so frequently ?
I know that 8 of them will run an XML on 2 primary CR123s but 4 of them will not. I just don't understand the role/function the AMC7135.
What exactly is it doing to control what gets to the emitter ?

The AMC7135 is a chip that dictate how much current ur emitter will get from the driver.

8 of the 350mA 7135 will draw approximately 2.8A & 4 * 7135 will draw about 1.4A.

Some 7135 driver have different voltage range, some up to 6V while some up till 4.5V.
The former will allow u to use 2 Cr123 while the latter only allows 1 lithium cell.
You might wanna check the voltage range of your drivers that you have.

- JonK

#### uk_caver

##### Flashlight Enthusiast
The 7135 is a linear constant current regulator.

Oversimplifying, it could be imagined to be rather like an 'intelligent resistor', which measures the current flowing through it between its two main connections, and keeps adjusting its resistance to try and keep that current at its target level.

Due to the way it operates, it is possible to connect multiple 7135s in parallel and each one of them will still work to keep the current flowing in them constant without upsetting their neighbours, giving a total current which is just the sum of all the individual currents.

#### DellSuperman

##### Flashlight Enthusiast
Due to the way it operates, it is possible to connect multiple 7135s in parallel and each one of them will still work to keep the current flowing in them constant without upsetting their neighbours, giving a total current which is just the sum of all the individual currents.

Yeah, "piggy back" is the word.

- JonK

#### SteveoMiami

##### Newly Enlightened
2 X CR123 is 6 Volts. Thats too much voltage and will fry AMC 7135 chips

#### Tedfs

##### Newly Enlightened
2 X CR123 is 6 Volts. Thats too much voltage and will fry AMC 7135 chips

In theory but I've been running 2x CR123s through 7135 chips on multiple lights for almost 3 years now.

#### LilKevin715

##### Enlightened
The 7135 is a linear constant current regulator.

Oversimplifying, it could be imagined to be rather like an 'intelligent resistor', which measures the current flowing through it between its two main connections, and keeps adjusting its resistance to try and keep that current at its target level.

Due to the way it operates, it is possible to connect multiple 7135s in parallel and each one of them will still work to keep the current flowing in them constant without upsetting their neighbours, giving a total current which is just the sum of all the individual currents.

+

AMC7135 linear regulators need 0.12v (more like 0.15-0.2v because of resistance) Vin (battery) above the Vf of the LED to stay in regulation to deliver the desired current to the LED.

Excess Vin above the LED Vf is burned off as heat. Excess Volts X Amps = Watts of burned off heat. Hence the intelligent/smart resistor.

SteveoMiami:
6v wont fry the chips as they are rated for a absolute max of 7v. In reality 2 X CR123 cells under load is closer to 5v.

#### SteveoMiami

##### Newly Enlightened
Awesome, thats great news for me, Now I have the perfect chip for the surefire build im working on!!!!

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#### SteveoMiami

##### Newly Enlightened
Hmmmm good point. I have 3 identical Rosche F12 lights I think Im going to put a fully charged 18650 in 1, 2 surefires in the second the third one is fully potted with thermal compound(homemade) see how the heat compares.