MSL2041 datasheet(13/20 Pages) ATMEL

13 / 20 page

Atmel LED Drivers-MSL2041/2042

but because LEDs differ, the number of shorted LEDs

required to generate a fault varies. The current fold-back

option, available through the serial interface, slightly

changes the fault response when an LED short circuit

event is suspected.

A string with an open circuit LED is off by default, and

when this situation is verified the faulty string is disabled

and no longer monitored by the Efficiency Optimizer.

Toggling EN low and then high clears all faults and the

MSL2041/2 begin to control and monitor all strings as

if experiencing an initial power-up. Fault conditions that

persist re-establish fault responses.

Faulty strings are flagged in the fault registers. When

using the serial interface, fault conditions are typically

read in response to FLTB pulling low.

Figure 3. Open-Circuit and Short-Circuit Detection Block Diagram

Figure 3. Open-circuit and Short-circuit Detection Block Diagram

Over Temperature Shutdown

The MSL2041/2 includes an automatic over-

temperature shutdown. If the die temperature exceeds

135°C, the device turns off, just as if the enable input

EN is forced low. When the die temperature drops

below 120°C the device wakes up again and turns on

as if experiencing an initial power-up.

Connecting the Efficiency Optimizer to an LED

String Power Supply and Selecting Resistors

The MSL2041/2 are designed to control LED string

power supplies that use a voltage divider (R

TOP and

BOTTOM in Figure 4) to set output voltage, and whose

regulation feedback voltage is not more than 3.5V - V

The Efficiency Optimizer improves power efficiency

by injecting a current of between 0µA and 280.5µA

into the voltage divider of the external power supply,

dynamically adjusting the power supply’s output to the

minimum voltage required by the LED strings.

Each of the two EOs monitors two LED strings. Strings

zero and one are assigned to FBO1, and strings two and

three are assigned to FBO2 (Table 1). When a single

supply is used for all four strings connect FBO2 to FBI1

(Figure 4), as explained in the next section “Using

Multiple EOs/Devices to Control a Common Power

Supply”. The MSL2041/2 then automatically maximizes

efficiency for all strings. When two supplies are used,

connect FBO1 to the supply powering strings zero and

one, and connect FBO2 to the supply powering strings

two and three (Figure 5). For clarity, Figure 4 and

Figure 5 do not show the Source and Drain connections

between the devices and the MOSFETs.

Atmel LED Drivers-MSL2041/MSL2042

Low-cost, Simple 4-string LED Drivers with External Current Sink

MOSFETs, 5000:1 Dimming Range and Per String PWM Input

MSL2041 Datasheet(PDF) 13 Page - ATMEL Corporation

MSL2041 Datasheet(HTML) 13 Page - ATMEL Corporation

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