Document
MIC2287
MIC2287
Micrel, Inc.
1.2MHz PWM White LED Driver with OVP in 2mm × 2mm MLF™ and Thin SOT-23
General Description
The MIC2287 is a 1.2MHz pulse width modulated (PWM), boost-switching regulator that is optimized for constantcurrent, white LED driver applications. With a maximum output voltage of 34V and a switch current of over 500mA, the MIC2287 easily drives a string of up to 8 white LEDs in series, ensuring uniform brightness and eliminating several ballast resistors.
The MIC2287 implements a constant frequency, 1.2MHz PWM control scheme. The high frequency PWM operation saves board space by reducing external component sizes. The added benefit of the constant frequency PWM scheme as opposed to variable frequency topologies is much lower noise and input ripple injected back to the battery source.
To optimize efficiency, the feedback voltage is set to only 95mV. This reduces the power dissipation in the current set resistor and allows the lowest total output voltage, hence minimal current draw from the battery.
The MIC2287 is available with 3 levels of overvoltage protection, 15V, 24V, and 34V. This allows designers to choose the smallest possible external components with the appropriate voltage ratings for their applications.
The MIC2287 is available in low profile Thin SOT-23 5-lead and an 8-lead 2mm × 2mm MLF™ package options. The MIC2287 has a junction temperature range of –40°C to +125°C.
All support documentation can be found on Micrel’s web site at www.micrel.com.
Features
• 2.5V to 10V input voltage • Output voltage up to 34V • Over 500mA switch current • 1.2 MHz PWM operation • 95mV feedback voltage • Output Overvoltage Protection (OVP) • Options for 15V, 24V, and 34V OVP • <1% line and load regulation • <1µA shutdown current • Over-temperature protection • UVLO • Low profile Thin SOT-23-5 package option • 8-lead 2mm × 2mm MLF™ package option • –40°C to +125°C junction temperature range
Applications
• White LED driver for backlighting: - Cell phones - PDAs - GPS systems - Digital cameras - MP3 players - IP phones
• Photo flash LED driver • LED flashlights • Constant current power supplies
Typical Application
10µH
CMDSH-3
1-Cell Li Ion
MIC2287BD5
5 VIN
SW 1
1µF
4 EN
FB 3 95mV
GND
2
6.3Ω
0.22µF
1-Cell Li Ion
10µH
CMDSH-3
MIC2287-34BML
VIN SW 1µF EN OVP
FB GND
95mV 6.3Ω
0.22µF
3-Series White LED Driver in Thin SOT-23
6-Series White LED Driver with Output OVP in 2mm × 2mm MLF™-8
MLF and MicroLeadFrame are trademarks of Amkor Technology, Inc.
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
July 2005
1 M9999-070105
MIC2287
Ordering Information
Part Number
Marking Overvoltage
Code
Protection
MIC2287BD5
SGAA
N/A
MIC2287YD5
SGAA
N/A
MIC2287-15BML
SLA
15V
MIC2287-15YML
SLA
15V
MIC2287-24BML
SLB
24V
MIC2287-24YML
SLB
24V
MIC2287-34BML
SLC
34V
MIC2287-34YML
SLC
34V
Junction Temp. Range
Package
–40°C to 125°C Thin SOT-23-5
–40°C to 125°C Thin SOT-23-5
–40°C to 125°C 2mm x 2mm MLF™
–40°C to 125°C 2mm x 2mm MLF™
–40°C to 125°C 2mm x 2mm MLF™
–40°C to 125°C 2mm x 2mm MLF™
–40°C to 125°C 2mm x 2mm MLF™
–40°C to 125°C 2mm x 2mm MLF™
Lead Finish Standard Lead Free Standard Lead Free Standard Lead Free Standard Lead Free
Micrel, Inc.
Pin Configuration
FB GND SW 321
45 EN VIN TSOT-23-5 (BD5)
OUT 1 VIN 2 EN 3 GND 4
8 GND 7 SW 6 FB EP 5 NC
8-Pin MLF™ (BML) (Top View)
Fused Lead Frame
Pin Description
Pin Number Pin Number TSOT-23-5 2mm ×2mm MLF™
17
2
36
Pin Name SW GND FB
43
EN
52 —1 —4 —8 —5 — EP
VIN OVP AGND PGND NC GND
Pin Function Switch node (Input): Internal power BIPOLAR collector. Ground (Return): Ground. Feedback (Input): Output voltage sense node. Connect the cathode of the LED to this pin. A resistor from this pin to ground sets the LED current. Enable (Input): Logic high enables regulator. Logic low shuts down regulator. Supply (Input): 2.5V to 10V for internal circuitry. Overvoltage protection (Input): Connect to the output. Analog ground. Power ground. No connect (no internal connection to die). Ground (Return): Exposed backside pad.
M9999-070105
2
July 2005
MIC2287
Absolute Maximum Ratings(1)
Supply Voltage (VIN) ..................................................... 12V Switch Voltage (VSW) ......................................–0.3V to 34V Enable Pin Voltage (VEN) ................................... –0.3 to VIN FB Voltage (VFB) ............................................................. 6V Switch Current (ISW) ........................................................ 2A Ambient Storage Temperature (TS) .......... –65°C to +150°C ESD Rating(3) ............................................................... 2kV
Micrel, Inc.
Operating Ratings(2)
Supply Voltage (VIN)..........................................2.5V to 10V Junction Temperature Range (TJ) ............ –40°C to +125°C Package Thermal Impedance
2mm × 2mmMLF™ (θJA) ...............