I am looking at getting one of these led drivers from onsemi, http://www.onsemi.com/pub_link/Collateral/CAT4137-D.PDF to drive 5 superbright LEDS (3.3V, 20mA) using an Uno.
I will turn the LEDs on/off using a single digital pin connected to SHDN on the driver.
The application diagram in the driver data sheet only shows the LEDS in series. Could this driver also successfully be used with a parallel LED configuration?
"While in normal operation, the device will comfortably
deliver up to 30 mA of bias current into a string of up to 5
Why not just use a single transistor driven from Arduino pin to sink current from cathodes of 5 LEDs connected in parallel?
Thanks for your response.
My problem is that i will be powering the Arduino and the rest of the circuit using a 3.7V lipo battery, so the supply voltage will vary a bit. But i would like to have the LEDs working high brightness all the time with the varying input voltage.
Is it better to use something like this, http://www.linear.com/product/LT1763 with resistors?
The CAT4137 is a switching driver. It will boost the input voltage to light the 5 LEDs when placed in series. It's a bit more complex of a circuit with the inductor and schottky diode being something most people don't have on hand, but it'll do what you want.
If you're worried about the varying voltage from the LiPo, why not just monitor the battery voltage with the Arduino and adjust output appropriately?