TM
MP3204 – 6V, 1.3MHz WHITE LED DRIVER
APPLICATION INFORMATION
V
IN
2.5V to 6V
CMDSH-3
LED1
LED2
6
IN
EN
1
SW
OFF ON
4
2
MP3204
OV
FB
5
3
LED3
GND
MP3204_F02
Figure 2—Driving 3 White LEDs
A typical application circuit can be seen in
Figure 2. The 3 white LEDs can be driven from
a voltage supply range of 2.5V to 6V at an
output current of 20mA. A 0.22µF output
capacitor is sufficient for most applications but
an output capacitor of up to 1µF may be used.
A 22µH inductor with low DCR (inductor
resistance) is recommended for improved
efficiency. A 1µF ceramic capacitor is
recommended for the input capacitance in the
real system. Schottky diodes have fast recovery
times and a low forward voltage and are also
recommended. Schottky diodes with ratings of
100mA to 200mA are sufficient for use with the
MP3204. The switching characteristics during
normal operation can be seen in Figure 3. The
MP3204 has internal soft-start to limit the
amount of current through VIN at startup and to
also limit the amount of overshoot on the
output. The current limit is increased by a fourth
every 40µs, giving a total soft start time of
120µs.
V
SW
5V/div.
V
OUT
RIPPLE
(AC COUPLED)
50mV/div.
I
L
100mA/div.
MP3204_F03
Figure 3—Steady-State Operation
(V
IN
=3.6V, 3 LEDs, 20mA)
MP3204 Rev. 1.3
9/23/2005
www.MonolithicPower.com
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2005 MPS. All Rights Reserved.
5
MPS [ MONOLITHIC POWER SYSTEMS ]
