MSL2160 datasheet(21/28 Pages) ATMEL

21 / 28 page

Atmel LED Drivers-MSL2160/MSL2161

The MSL2160/1 are designed to control external LED string power supplies that use voltage dividers (R

TOP and RBOTTOM

in Figure 5) to set the output voltage, and whose regulation feedback voltage is not more than 3.5V. The Efficiency

Optimizer improves power efficiency by injecting a current of between 0 and 255µA into the voltage dividers of the

external power supplies, dynamically adjusting their outputs to the minimum voltage required by the LED strings. To

select the resistors, first determine V

OUT(MIN) and VOUT(MAX), the minimum and maximum string supply voltage limits, using:

[

]

(

) 5.

)

(

)

(

∗

ofLEDs

MIN

OUT

and

[

]

(

) 5.

)

(

)

(

∗

ofLEDs

MAX

OUT

where V

f(MIN) and Vf(MAX) are the LED minimum and maximum forward voltage drops at the peak current set by RS (page

12). For example, if the LED data are V

f(MIN) = 3.5V and Vf(MAX) = 3.8V, and ten LEDs are used in a string, then the total

minimum and maximum voltage drops across a string are 35V and 38V, respectively. Adding an allowance of 0.5V for the

string drive MOSFET headroom brings V

OUT(MIN) to 35.5V and VOUT(MAX) to 38.5V. Then, determine RTOP using:

)

(

)

(

)

(

MAX

FBOn

MIN

OUT

MAX

OUT

TOP

−

where I

FBOn(MAX) is the 255µA maximum output current of the efficiency optimizer outputs FBOn. Finally, determine RBOTTOM using:

MAX

OUT

TOP

BOTTOM

−

∗

)

(

where V

FB is the regulation feedback voltage of the power supply. Place a diode (1N4148 or similar) between FBOn and

the supply’s feedback node to protect the MSL2160/1 against current flow into FBOn. Assign all strings powered by a

common supply to the proper FBO output using string set registers 0x40 - 0x5F.

Once configured, determine the change in power supply output voltage in response to a change in FBO output current using:

TOP

FBO

OUT

∗

∆

Direct PWM Control of the LED Strings

An external PWM signal applied to the PWM input allows direct PWM control over the strings when bits PWMEN and

PWMDIRECT (bits D0 and D1 in PWM control register 0x2D) are set to 1. This configuration bypasses PHI and GSC, but

allows LED string phase delay via the phase delay enable bit, PHADLYEN (bit D0 of register 0x2E). With phase delay

enabled, a progressive delay of 1/16 the PWM frame is calculated and applied successively to each string drive signal.

The PWM input can also be configured as a gate for the output of the PWM engine using PWM global enable

(bit D2 of the PWM control register 0x2D).

Connecting the Efficiency Optimizer to an LED String Power Supply and Selecting Resistors

Atmel LED Drivers-MSL2160/MSL2161

16-string, White and RGB LED Drivers with Adaptive Configuration,

EEPROM, and SPI/I2C/SMBus Serial Interface

MSL2160 Datenblatt(PDF) 21 Page - ATMEL Corporation

MSL2160 Datenblatt(HTML) 21 Page - ATMEL Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Datenblatt Download

Link URL