MAX16840_15 Datasheet, PDF (11/12 Pages) Maxim Integrated Products – LED Driver with Integrated MOSFET

MAX16840
LED Driver with Integrated MOSFET
for MR16 and Other 12V AC Input Lamps
The output voltage of the LED string is given by VLED. As
a first-order approximation, the LED voltage is assumed
constant. The duty cycle at the peak of the input voltage
is, therefore:
D_MIN
= 1− ^{13.2V × 2}
V_LED + 13.2V ×
= 1− ^18.66V
2
V_LED + 18.66V
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:
IP-P = 1.3IIN
The minimum inductor value is given by:
L _MIN
=
18.66V × D_MIN2
0.6I_IN × 300kHz
where the switching frequency is 300kHz. The saturation
current of the inductor should be higher than IP-P and the
minimum value of the inductor at IP-P should exceed LMIN.
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 (foot-
prints), go to www.maximintegrated.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
10 TDFN-EP
PACKAGE
CODE
T1033+1
OUTLINE
NO.
21-0137
LAND
PATTERN NO.
90-0003
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