MP2488DN データシートの表示（PDF） - Monolithic Power Systems

部品番号

コンポーネント説明

一致するリスト

MP2488DN

200kHz, 55V Input, 2A High Power LED Driver

Monolithic Power Systems 

MP2488 – 2A, 200kHz, 55V HIGH-POWER LEDS DRIVER

Output Capacitor COUT

The output capacitor (COUT) is required to reduce

the LED current ripple. Ceramic, tantalum, or low

ESR electrolytic capacitors are recommended.

Low ESR capacitors are preferred to keep the

output voltage ripple low so that the AC ripple

current through the LEDs is small. The output

voltage ripple can be estimated by:

ΔVOUT



VOUT

8  fS2  L1 COUT

 1



VOUT

VIN







For most application, a 2.2uF~4.7uF ceramic

capacitor is recommended.

Compensation Components

MP2488 employs current mode control for easy

compensation and fast transient response. The

system stability and transient response are

controlled through the COMP pin. COMP pin is

the output of the internal error amplifier. A series

capacitor-resistor combination (RCOM and CCOM1)

sets a pole-zero combination to control the

characteristics of the control system. The DC

gain of the current feedback loop is given by:

A VDC  RFB  GCS  A VEA

Where AVEA is the error amplifier voltage gain,

400V/V; GCS is the current sense

transconductance, 8A/V; RFB is the current

sensing resistor value.

The system has two poles of importance. One is

due to the compensation capacitor (CCOM1) and

the output resistor of error amplifier

(REA=AVEA/GEA). GEA is the error amplifier

transconductance, 500μA/V. The other is due to

the output capacitor and the LEDs’ AC resistor

(RLED=VOUT/ILED). These poles are located at:

fP1



2 

1

CCOM1

 REA

fP2



1

2  COUT

 RLED

The system has one zero of importance, due to

the compensation capacitor (CCOM1) and the

compensation resistor (RCOM). This zero is

located at:

fZ1



1

2  CCOM1

 RCOM

The system may have another zero of

importance, if the output capacitor has a large

capacitance and/or a high ESR value. The zero,

due to the ESR and capacitance of the output

capacitor, is located at:

fESR



1

2  COUT

 RESR

In this case, a third pole set by the compensation

capacitor (CCOM2) and the compensation resistor

(RCOM) is used to compensate the effect of the

ESR zero on the loop gain. This pole is located

at:

fP3



1

2  CCOM2

 RCOM

The goal of compensation design is to shape the

converter transfer function to get a desired loop

gain and phase margin. The system crossover

frequency where the feedback loop has the unity

gain is important. Lower crossover frequencies

result in slower line and load transient responses,

while higher crossover frequencies could cause

system unstable. A good rule of thumb is to set

the crossover frequency to approximately one-

tenth of the switching frequency. To optimize the

compensation components for conditions, the

following procedure can be used.

1. Choose the compensation resistor (RCOM) to

set the desired crossover frequency. Determine

the RCOM value by the following equation:

RCOM



2  COUT  RLED 

RFB  GEA  GCS

fC

Where fC is the desired crossover frequency.

2. Choose the compensation capacitor (CCOM1) to

achieve the desired phase margin. For

applications with typical inductor values, setting

the compensation zero, fZ1, below one forth of the

crossover frequency provides sufficient phase

margin. Determine the CCOM1 value by the

following equation:

CCOM1



2

4

 RCOM



fC

MP2488 Rev. 1.0

www.MonolithicPower.com

10

6/20/2011

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2011 MPS. All Rights Reserved.

Share Link: