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<h1>How to choose an LED driver IC</h1>
<p>An LED is a current-fed device. A resistor from a stiff rail is acceptable for an indicator that can tolerate a dim glow when the supply sags and a short life when it does not. Anything that must hold a brightness, a color, or a safety-related intensity needs a driver that regulates current. The choice is which topology, and how the dimming is done.</p>
<p>Match the topology to the voltages. If the LED string voltage is always below the supply, a linear current sink is quiet, small, and wasteful in proportion to the voltage it drops. If the string is above the supply, you need a boost. If it can be either, a buck-boost or a SEPIC avoids a dead zone. The current accuracy and the sense voltage decide efficiency. A 200 millivolt sense resistor wastes less than an older part that uses a volt, but it is also more sensitive to layout and to the offset of the error amplifier. Read the current accuracy over temperature, because an outdoor lamp sees the whole range.</p>
<p>Dimming method changes the optical result. PWM dimming keeps the color point stable because the LED is either at the design current or off. Analog dimming is simpler and can be silent, but the color shifts at low current and some emitters look green. Hybrid schemes do both. The dimming ratio you promise to a customer has to include the minimum on-time of the converter, not just the resolution of the PWM counter. A converter that cannot produce a 1 microsecond pulse will not deliver a 1000 to 1 ratio at 1 kHz.</p>
<p>Open-LED and shorted-LED behavior should be specified. A boost that loses its load will run away unless the driver stops. Thermal foldback is worth having on a sealed luminaire. The package has to get the heat out of the switch, not just out of the datasheet.</p>
<p>For constant-current parts grouped away from general-purpose regulators, <a href="https://chipapex.com/led-drivers-ic/">LED driver ICs</a> are easier to sort when topology, sense voltage, and dimming method are visible together.</p>
<p>Write the LED voltage at cold and at hot, the supply range, and the dimming ratio before you pick a part number. Those three constraints remove most of the catalog.</p>
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