MP2481 –36V, 1.2A, 1.4MHz WHITE LED DRIVER
MP2481 Rev. 1.43 www.MonolithicPower.com 4
7/10/2014 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2014 MPS. All Rights Reserved.
PIN FUNCTIONS
Pin # Name Description
1 VDD
Supply Voltage. The MP2481 operates from a +4.5V to +36V unregulated input (with respect
to VSS). C1 is needed to prevent large voltage spikes from appearing at the input.
2 VSS
Power Return Pin. Connect to the lowest potential in the circuit, which is typically the anode
of the Schottky rectifier. This pin is the voltage reference for the regulated output voltage.
For this reason care must be taken in its layout. This node should be placed outside of the
D1 to C1 ground path to prevent switching current spikes from inducing voltage noise into
the part. The exposed pad is also connected to this pin.
3 OVP
Over Voltage Protection Pin. Use one external resistor voltage divider to program OVP
threshold. When the OVP pin voltage (with respect to VSS) is lower than 0.4V, the chip
frequency will be folded back. Program the OVP pin voltage from 0.4V to 1.23V for normal
operation. When the OVP pin voltage reaches the shutdown threshold 1.23V, the switch will
be turned off
4 FB
LED Current Feedback Input. MP2481 regulates the voltage across the current sensing
resistor between FB and VSS. Connect the current sensing resistor from the bottom of the
LED strings to VSS. The FB pin is connected to the bottom of the LED strings. The
regulation voltage is 0.2V.
5 EN/DIM
On/Off Control Input and Dimming Command Input. A voltage greater than 0.7V will turn on
the chip. When the EN/DIM pin voltage (with respect to INGND) rises from 0.7V to 1.4V, the
LED current will change from 0% to 100% of the maximum LED current. To use PWM
dimming, apply a 100Hz to 1kHz square wave signal with amplitude greater than 1.4V to this
pin.
6 INGND Input Ground Reference. This pin is the reference for the EN/DIM signal.
7 BST
Bootstrap. A capacitor is connected between SW and BST pins to form a floating supply
across the power switch driver. This capacitor is needed to drive the power switch’s gate
above the supply voltage.
8 SW
Switch Output. SW is the source of the internal MOSFET switch. Connect to the power
inductor and cathode of the Schottky rectifier.
