0
\$\begingroup\$

UPDATE (2021-Jan-16) - All working as expected - Project link for anyone to build or do as they please.

PAM2804, I've been trying to use this chip for a single Li-ion cell flashlight project, but it does not work for me. I've designed 2 PCBs so far, but both failed.

I'm driving a Cree X-Lamp XML @ 1A.

I can see voltage on the output, but the LED does not light.

1st PCB was a 2 layer; 2nd PCB was a 4 layer with 2 inner ground layers.

Anyone kindly point out what I might be doing wrong please?

Components used;

enter image description here

My schematics: **

  • For testing I have only solder the PAM2804 side. For now ignore reset of the circuitry please.
  • Direct power injected from a charged Li-ion battery at C1.
  • Sorry I have no oscilloscope at the moment. It's on it's way. **

enter image description here

My 2nd PCB:

enter image description here

Voltages at;

enter image description here

U1 Pin 1 - 4.092v

U1 Pin 2 - 3.258v strange this is GND

U1 Pin 3 - Starts at 3.3v and goes down to 3.089v and stables.

U1 Pin 4 - 4.092v (same as C1 voltage)

U1 Pin 5 - Starts at 3.475v and goes down to 3.369v and stables.

C1 - 4.092v

C7 - Starts at 3.3v and goes down to 3.085v and stables.

\$\endgroup\$
6
  • \$\begingroup\$ What is the DC voltage on pin 4 of the PAM2804? Is it perhaps too low to get the required 2.98 volts needed for the LED at 1000 mA? \$\endgroup\$ – Andy aka Jan 14 at 18:07
  • \$\begingroup\$ No component specs. No measurements. No answers. You need to offer clues of failures. \$\endgroup\$ – Tony Stewart EE75 Jan 14 at 18:18
  • 2
    \$\begingroup\$ "i see voltage" ... voltage is a little vague ... any particular voltage, and how does in compare with the forward voltage of your LED? \$\endgroup\$ – user_1818839 Jan 14 at 18:39
  • 2
    \$\begingroup\$ You perhaps have a solder short over small gaps. Record voltage on every pin on schematic \$\endgroup\$ – Tony Stewart EE75 Jan 15 at 1:15
  • 2
    \$\begingroup\$ "U1 Pin 2 - 3.258v strange this is GND" - Dry joint on pin 2? Measuring between wrong points? Don't just leave it at that - find out why your 'GND' is not ground! \$\endgroup\$ – Bruce Abbott Jan 15 at 6:49
0
\$\begingroup\$

I had a pretty similar circuit 2 months ago, using TP4056 with PAM. Since, you are getting the output voltage, only other fault could be coming from lack of current. I would check if

  • Amperage and ESR of Inductor L1, are within specified tolerances (0.1 value of R1 will require atleast 1.5amp rated inductor, and LED you are driving requires a minimum of 700mA)
  • C1 is MLCC
  • C2, C7 could be Tantalum
\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.