MP24183 – 1A, 55V, PROGRAMABLE FREQUENCY WHITE LED DRIVER
MP24183 Rev. 1.0 www.MonolithicPower.com 4
8/28/2008 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2011 MPS. All Rights Reserved.
PIN FUNCTIONS
Pin # Name Description
1 VDD
Supply Voltage. The MP24183 operates from a +4.5V to +55V 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 a voltage divider to program OVP threshold. When the
OVP pin voltage reaches the shutdown threshold 1.2V, the switch will be turned off and will
recover when OVP voltage decreases sufficiently. When the OVP pin voltage (with respect
to VSS) is lower than 0.4V and FB pin voltage is lower than 0.1V, the chip reecognizes this
as short circuit condition and the operating frequency will be folded back. Program the OVP
pin voltage from 0.4V to 1.2V for normal operation.
4 FB
LED Current Feedback Input. MP24183 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 0.198V.
5 COMP
Output of error amplifier. Connect a 1nF or larger capacitor on COMP to improve the
stability and to provide a soft on at start up and PWM dimming.
6 RSET
Frequency Set Pin. Connect a resistor to VSS to set the switching frequency and an 1nF
capacitor to VSS to bypass the noise. Leaving this pin open gets a default operating
frequency 1.35MHz.
7 EN/DIM
On/Off Control Input and Dimming Command Input. A voltage greater than 0.6V will turn on
the chip. Both DC and PWM dimming are implemented on this pin. 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 2kHz
square wave signal with amplitude greater than 1.4V to this pin.
8 INGND Input Ground Reference. This pin is the reference for the EN/DIM signal.
9 BST
Bootstrap. A capacitor is connected between SW and BST pin to form a floating supply
across the power switch driver. A 100nF or larger ceramic capacitor is recommended to
provide sufficient energy to drive the power switch’s gate above the supply voltage.
10 SW
Switch Output. SW is the source of the internal MOSFET switch. Connect this pin to the
power inductor and the cathode of the Schottky rectifier.
Exposed pad should be connected to VSS in step up/down mode.
