Datasheet

14 Atmel LED Driver-MSL3162
Detailed Description
Internal Regulators and Enable Input
Built-in current control MOSFETs capable of withstanding
up to 40V provide a compact solution. The Efficiency
Optimizer circuit controls the LED voltage generated
by an external DC-DC converter to minimize losses on
the current control MOSFETs, improving efficiency and
reducing driver power dissipation. The MSL3162 uses
a high-speed, 1MHz I
2
C serial interface to control LED
current, PWM dimming, and fault detection circuitry,
making it an optimal solution for driving LED backlights
for LCD panels. Onboard EEPROM allows default settings
to be reconfigured for customization and settings to be
saved at turn-off, eliminating the need to re-write settings
at the next turn-on. The tiny, 6mm x 6mm QFN package
enables a compact solution while maintaining high power
dissipation.
Internal Regulators and Enable Input
The MSL3162 includes an internal linear regulator that
provides 2.5V supply voltage to power internal circuitry.
Bypass VDD to GND with a 1µF or greater capacitor as close
to the MSL3162 as possible.
The EN input turns the MSL3162 on and off. To turn
on the MSL3162, drive EN high with a 5V logic level,
and drive EN low to turn it off. When EN is low, the
MSL3162 enters low-power mode, reducing input
current to 20µA, and turns off the serial interface. For
automatic start-up, connect EN to VIN, allowing the
MSL3162 to start automatically when voltage is applied.
LED String Current Control
Each MSL3162 includes 16 current sink outputs, rated
at 40V, each capable of sinking up to 100mA through a
string of series connected LEDs. The internal Efficiency
Optimizer circuit controls the LED voltage, minimizing
power dissipated in the current sinks while maintaining
high current-regulation accuracy. The MSL3162 power
dissipation is limited to 2.1W. When using all 16 current
sinks, maintain the total power dissipation within power
dissipation limits.
Setting the Maximum LED String Current
The maximum I
ILED
current for the 16 LED strings STR0
to STR15 is set by external resistor R
ILED
from the ILED
pin to GND and is determined by the equation:
ILED
ILED
R
I
2050
=
where I
ILED
is in mA and R
ILED
is in kΩ.
R
ILED
=34.8kΩ sets the full-scale LED current to 58.9mA.
R
ILED
=20.5kΩ sets the full-scale LED current to 100mA,
the maximum allowed. The currents for the 16 LED
strings, STR0 to STR15, are reduced individually from
full scale with 6-bit resolution using the LED string
current control registers.
If I
ILED
for the 16 LED strings, STR0 to STR15, is chosen
to be 30mA or lower (by selecting the value of external
resistor R
ILED
to be greater than 68.3kΩ), then the
values programmed into the LED string current control
registers must be limited to the range 0x00 to 0x1F.
The full range of 0x00 to 0x3F is only available if I
ILED
is
set to be greater than 30mA by using an R
ILED
value of
68.3kΩ or lower.