MP3389—12-STRING WHITE LED DRIVER WITH STEP-UP CONTROLLER
MP3389 Rev. 1.04 www.MonolithicPower.com 5
3/27/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
PIN FUNCTIONS
Pin # Name Description
1 NC No Connect.
2 VIN
Supply Input. VIN supplies the power to the chip, as well as the step-up converter switch. Drive
VIN with a 5V to 28V power source. Must be locally bypassed.
3 VCC
The Internal 5V Linear Regulator Output. VCC provides power supply for the internal MOSFET
switch gate driver and the internal control circuitry. Bypass VCC to GND with a ceramic
capacitor.
4 COMP
Step-up Converter Compensation Pin. This pin is used to compensate the regulation control
loop. Connect a capacitor or a series RC network from COMP to GND.
5 EN Enable Control Input. Do not let this pin floating.
6 DBRT
Brightness Control Input. To use external PWM dimming mode, apply a PWM signal on this pin
for brightness control. To use DC input PWM dimming mode, apply a DC voltage range from
0.2V to 1.2V on this pin linearly to set the internal dimming duty cycle from 0% to 100%. The
MP3389 has positive dimming polarity on DBRT.
7 GND Analog Ground.
8 OSC
Switching Frequency Set. Connect a resistor between OSC and GND to set the step-up
converter switching frequency. The voltage at this pin is regulated to 1.23V. The clock frequency
is proportional to the current sourced from this pin.
9 ISET
LED Current Set. Tie a current setting resistor from this pin to ground to program the current in
each LED string. The MP3389 regulates the voltage across the current setting resistor. The
regulation voltage is 1.22V. The proportion of the current through the ISET resistor and the LED
current is 1:1000.
10 BOSC
Dimming Repetition Set. This is the timing pin for the oscillator to set the dimming frequency. To
use DC input PWM dimming mode, connect a capacitor from this pin to GND to set the internal
dimming frequency. A saw-tooth waveform is generated on this pin. To use external PWM
dimming mode, connect a 100k resistor from this pin to GND, and apply the PWM signal on
DBRT pin.
11 LED12
LED String 12 Current Input. This pin is the open-drain output of an internal dimming control
switch. Connect the LED String 12 cathode to this pin. If this string is not used, connect Vin to
this pin.
12 LED11
LED String 11 Current Input. This pin is the open-drain output of an internal dimming control
switch. Connect the LED String 11 cathode to this pin. If this string is not used, connect Vin to
this pin.
13 LED10
LED String 10 Current Input. This pin is the open-drain output of an internal dimming control
switch. Connect the LED String 10 cathode to this pin. If this string is not used, connect Vin to
this pin.
14 LED9
LED String 9 Current Input. This pin is the open-drain output of an internal dimming control
switch. Connect the LED String 9 cathode to this pin. If this string is not used, connect Vin to this
pin.
