Datasheet

20 Atmel LED Drivers-MSL2160/MSL2161

Figure 5. FBOn Connects to the Power Supply Voltage Divider Through a Diode.

LED

5.0

, where I

LED

is in amperes and R

is in ohms.

For example, a full-scale LED current of 100mA returns R

= 5Ω. The current for all LED strings is reduced

from the full-scale value with 8-bit resolution using ISTR, the string current control register 0x31.

Internal Regulators and Enable Input

The MSL2160/1 includes two internal linear regulators that provide VCC (5V) and VDD (2.5V) for internal circuitry. VIN

(12V nominal) supplies the VCC and VDD regulators. Bypass VIN to GND with a 10µF capacitor close to the device. Bypass

VCC to GND with a 4.7µF capacitor close to the device. Bypass VDD to GND with a 4.7µF capacitor close to the device.

The MSL2160/1 enables input, EN, enables the device. Drive EN low to enter low power operation, which lowers

quiescent current draw to less than 20µA. With EN low, the serial interface is ignored, the Efficiency Optimizer is disabled,

and all strings are turned off. Drive EN high to turn on the device. When EN is driven high, the contents of the EEPROM

are boot loaded into the control registers, simulating a cold start up, and all bits in the fault registers are cleared to 0.

Setting the Maximum LED String Current with a Source Resistor

The maximum string current, I

LEDn

, for each string is set by a shunt resistor connected to ground from the source terminal

of the string drive MOSFET. The feedback threshold is 500mV. Determine the resistor value using: