Max16820att high power led string driver

Led headlights are beginning to emerged from the open although there is still no true led headlight available in the market, they are still on the experimental stages for beam, focus, reliability, and if there was, it will be expensive.So why not experiment with leds and come up with your own. Using one Ic and some discrete components, you can do so.

 In this page, tried using max16820at+t by maxim

The MAX16819/MAX16820, step-down constant-current high-brightness LED (HB LED) drivers provide a cost-effective solution for automotive interior/exterior lighting, architectural and ambient lighting, LED bulbs such as MR16 and other LED illumination applications.

The MAX16819/MAX16820 operate from a 4.5V to 28V input voltage range and feature a 5V/10mA on-board regulator. A high-side current-sense resistor adjusts the output current and a dedicated PWM input (DIM) enables a wide range of pulsed dimming.




The MAX16819/MAX16820 are well suited for applications requiring a wide input voltage range. The high-side current-sensing and an integrated current-setting circuitry minimize the number of external components while delivering an LED current with ±5% accuracy. A hysteretic control algorithm ensures excellent input-supply rejection and fast response during load transients and PWM dimming. The MAX16819 features a 30% inductor current ripple and the MAX16820 features a 10% current ripple. These devices operate up to 2MHz switching frequency, thus allowing for small component size

The CIRCUIT

With minimal external component, we can create a led string driver for a maximum of 4 led in series with a constant current drive of 2A maximum. Current for the led is simply calculated for Rsense value and table below show the value and output current possible.

For 700mah series of 4 high brightness led, shows that 0.33 ohms can be used for Rsense value.

 Board and placement

All parts used except for D, L and Rsense are all smd type or on board placement.

Parts:

Rsense= see table
D- fast diode 3A 30-60v (SR360)
L- 40uh 3A coil
IC- max16820att
Q- IRLL2705
Cvcc- 1uf / 25v
Cin / Cout - 1uf / 50v

At first i had trouble powering her up, my attempt was fail..it was the soldered of max16820att to the board. and after checking i have soldered the pins correctly, i was surprised of the light, powerful enough with right current for the led of 700mah, no parts are actually heating up..sign of a good converter.

 Ready for test...

and there was light...

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