MP1521

High Efficiency

White LED Driver

MP1521 Rev 2.7 10/06/04

www.monolithicpower.com

3

Monolithic Power Systems

Pin Description

MSOP10

QFN16

Part Marking: MP1521EK

Part Marking: A1xx

Table 1: MP1521 MSOP10 and QFN16 Pin Assignments

MSOP

Pin #

QFN

Pin#

Pin

Name

Pin Function

1

16

IN

Input supply pin. It can be connected to the regulator’s input supply, or to the

less than 3V).

2

2

EN

into low current shutdown mode. Place a 100K

Ω resistor in series with EN if it is

connected to a voltage greater than 10V.

3

4

REF

1.23V reference used for setting the analog control voltage at BRT input. This

reference can supply up to 200

µA to an external load. Do not connect any

bypass capacitors to this pin. It is internally compensated.

4

5

BRT

Analog or PWM input for controlling LED brightness. When used in analog

mode, apply a DC voltage of 0.3 to 1.2V. This input voltage is attenuated by 1/3

to set the voltage across sense resistors at FB1, FB2, and FB3. Maximum

brightness (20mA) occurs with 1.2V applied. To control brightness in PWM

mode, apply a PWM square wave with a minimum voltage less the 0.18V and a

maximum greater than 1.2V. When a voltage less than 0.18V is applied to this

pin, the output switch is turned off.

The regulator operates at maximum

brightness when more than 1.2V is applied. The frequency of the PWM signal

must be between 100 to 400 Hz.

5

6

7

7

8

9

FB3

FB2

FB1

Feedback input for measuring voltage across current-sense resistor that is in

series with LED string. Unused feedback pins must be connected to any used

feedback pin.

8

10

OLS

Open Load Shutdown pin senses regulator output voltage to protect IC during

open load operation. When this pin’s voltage exceeds 28V, the output switch is

shut off. The output switch remains off until the IC is reset by cycling the enable

pin (EN) or input supply (IN) pin.

9

11, 12

GND

Signal and power ground. Connect directly to ground plane.

10

14

SW

Output switch pin, power DMOS low-side switch.

-

1, 3, 6,

13, 15

N/C

No Connect

SW

GND

OLS

FB1

FB2

IN

EN

REF

BRT

FB3

1

2

3

4

5

10

9

8

7

6

NC

EN

NC

REF

Top

View

GND

GND

OLS

FB1

1

2

3

4

12

11

10

9