Datasheet

LED Driver with Integrated MOSFET
for MR16 and Other 12V AC Input Lamps
The output voltage of the LED string is given by V
LED
. As
a first-order approximation, the LED voltage is assumed
constant. The duty cycle at the peak of the input voltage
is, therefore:
×
= − = −
+
+ ×
MIN
LED
LED
13.2V 2 18.66V
D 1 1
V 18.66V
V 13.2V 2
The percentage
P-P
ripple is typically selected in the 30%
to 60% range of the maximum input current. Assuming
a 60%
P-P
inductor-current ripple, the maximum inductor
current is given by:
I
P-P
= 1.3I
IN
The minimum inductor value is given by:
2
MIN
MIN
IN
18.66V D
L
0.6I 300kHz
×
=
×
where the switching frequency is 300kHz. The saturation
current of the inductor should be higher than I
P-P
and the
minimum value of the inductor at I
P-P
should exceed L
MIN
.
Output Diode (D1)
A Schottky diode must be used as rectifier diode D1 to
reduce power dissipation. The voltage rating of diode D1
must be greater than the maximum peak input voltage
plus the maximum output voltage. Choose a diode that
minimizes dissipation at temperatures in the +90NC to
+100NC range. The diode should be selected to minimize
reverse leakage at the maximum output voltage while
minimizing forward losses when the diode is conducting.
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maxim-ic.com/packages. Note that a
“+”, “#”, or “-” in the package code indicates RoHS status only.
Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
10 TDFN-EP T1033+1
21-0137 90-0003
Maxim Integrated
11
MAX16840
Maxim Integrated
11