EV0021
MP1521 High Efficiency
White LED Driver
EVALUATION BOARD
EV0021 Rev 1.1_01/21/03 www.monolithicpower.com 1
Monolithic Power Systems
General Description
The EV0021 evaluation board uses the
MP1521 to drive up to three strings of 5 White
LEDs. This MP1521 uses a peak current,
constant minimum off-time architecture and
has three individual current-sensing
feedbacks. The OLS pin is designed for
detecting loose or open LED connections.
The feedback pins measure voltage across
sense resistors in series with the LED strings.
When supplying a bias current of 20mA, the
voltage drop across the sense resistor is only
0.4V to minimize power loss. Either a DC
voltage or a PWM signal at the BRT/PWM
input can control the LED brightness. The
MP1521 has an on board power MOSFET
switch that is protected by current limit, open
load shutdown, thermal shutdown, and under
voltage lockout.
Ordering Information
Board Number MPS IC Number
EV0021 MP1521EQ
Absolute Maximum Ratings
Supply Voltage (VIN) 28V
Switch Voltage to GND -0.5V to 28V
VEN,VREF, VBRT, VFB1, VFB2, VFB3 –0.3V to 6V
Storage Temperature -55°C to +150°C
Recommended Operating Conditions
Supply Voltage (VIN) 2.7 V to 25V
Figure 1: EV0021 Evaluation Board
EV0021
MP1521 High Efficiency
White LED Driver
EVALUATION BOARD
EV0021 Rev 1.1_01/21/03 www.monolithicpower.com 2
Monolithic Power Systems
Figure 2: EV0021 Schematic
EV0021
MP1521 High Efficiency
White LED Driver
EVALUATION BOARD
EV0021 Rev 1.1_01/21/03 www.monolithicpower.com 3
Monolithic Power Systems
Table 1: EV0021 Bill of Materials
Parts Package Vendor QTY Components
ICs
MP1521EQ QFN16 MPS 1 U1
Capacitors
4.7µF 1206 Any 1 C1
1µF, 25V 1210 Any 1 C2
Resistors
10KΩ 0603 Any 3 R1, R2, R3
20Ω 0603 Any 3 R4, R5, R6
Inductors
15µH CDRH3D16 Sumida 1 L1
Diodes
B130, 1A, 30V, Schottky SMA Any 1 D1
LEDS (Not Provided)
Operating Instructions
1. Connect VCC to the power source’s positive output.
2. Connect GND to supply ground.
3. Applying a logic signal to EN pin will enable the MP1521. Logic high (VEN>1V) turns on IC,
logic low puts it into low current shutdown mode. Place a 100KΩ resistor in series with EN if
the input is greater than 10V. For automatic start up connect EN to VCC.
4. Applying a PWM signal to the BRT will adjust the 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. The FB1, FB2 and FB3 pins can be used to measure the voltage across the current-sense
resistor that is in series with the LED strings. Unused feedback pins must be connected to
any used feedback pin.
6. OLS senses the 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 (VIN)
EV0021
MP1521 High Efficiency
White LED Driver
EVALUATION BOARD
EV0021 Rev 1.1 Monolithic Power Systems, Inc. 4
01/21/03 3777 Stevens Creek Blvd, Suite 400, Santa Clara, CA 95051-7364 USA
© 2003 MPS, Inc. Tel: (408) 243-0088, Fax: (408) 243-0099, Web: www.monolithicpower.com
Monolithic Power Systems
Figure 3: EV0021 Top Silk Layer
Figure 4: EV0021 Top Layer
Figure 5: EV0021 Bottom Layer
NOTICE: MPS believes the information in this document to be accurate and reliable. However, it is subject to change
without notice. Please contact the factory for current specifications. No responsibility is assumed by MPS for its use or
fit to any application, nor for infringement of patent or other rights of third parties.
