MIC2287 Micrel Semiconductor, MIC2287 Datasheet

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MIC2287

Manufacturer Part Number
MIC2287
Description
1.2MHz PWM White LED Driver with OVP in 2mm 2mm MLF and Thin SOT-23
Manufacturer
Micrel Semiconductor
Datasheet

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General Description
The MIC2287 is a 1.2MHz pulse width modulated (PWM),
boost-switching regulator that is optimized for constant-
current, 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 protec-
tion, 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
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.
Typical Application
MLF and
August 2004
MIC2287
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
1-Cell
Li Ion
3-Series White LED Driver in Thin SOT-23
Micro
LeadFrame are trademarks of Amkor Technology, Inc.
1 F
5
4
2mm MLF™ package options. The
MIC2287BD5
VIN
EN
10 H
GND
2
SW
FB
1
3
95mV
CMDSH-3
6.3
0.22 F
1
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
• <1 A shutdown current
• Over-temperature protection
• UVLO
• Low profile Thin SOT-23-5 package option
• 8-lead 2mm
• –40 C to +125 C junction temperature range
Applications
• White LED driver for backlighting:
• Photo flash LED driver
• LED flashlights
• Constant current power supplies
1.2MHz PWM White LED Driver with OVP in
- Cell phones
- PDAs
- GPS systems
- Digital cameras
- MP3 players
- IP phones
1-Cell
Li Ion
2mm
with Output OVP in 2mm
2mm MLF™ and Thin SOT-23
6-Series White LED Driver
2mm MLF™ package option
1 F
MIC2287
MIC2287-34BML
VIN
EN
10 H
GND
OVP
SW
FB
CMDSH-3
95mV
2mm MLF™-8
6.3
M0510-081104
0.22 F
Micrel

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MIC2287 Summary of contents

Page 1

... LED driver applications. With a maximum output voltage of 34V and a switch current of over 500mA, the MIC2287 easily drives a string white LEDs in series, ensuring uniform brightness and eliminating several ballast resistors. The MIC2287 implements a constant frequency, 1.2MHz PWM control scheme ...

Page 2

... MIC2287 Ordering Information Marking Overvoltage Part Number Code Protection MIC2287BD5 SGAA MIC2287YD5 SGAA MIC2287-15BML SLA MIC2287-15YML SLA MIC2287-24BML SLB MIC2287-24YML SLB MIC2287-34BML SLC MIC2287-34YML SLC Pin Configuration FB GND VIN TSOT-23-5 (BD5) Pin Description Pin Number Pin Number TSOT-23-5 2mm 2mm MLF™ ...

Page 3

... I 20mA OUT 10V EN SW TURN ON TURN OFF V = 10V EN MIC2287BML- 15 only MIC2287BML- 24 only MIC2287BML- 34 only Hysteresis , and the ambient temperature The maximum allowable power dissipation will result in excessive (2) ) ........................................ 2.5V to 10V IN ) ........... – +125 C J 2mmMLF™ ..................................... 93 C .......................................... 256 C 125 C. ...

Page 4

... MIC2287 Typical Characteristics Feedback Voltage vs. Input Voltage 100 ( Series LED Efficiency 0.22 F OUT (mA) OUT EN Pin Bias Current vs. Temperature 50 45 ...

Page 5

... REF 95mV * OVP available on MLF Functional Description The MIC2287 is a constant frequency, PWM current mode boost regulator. The block diagram is shown above. The MIC2287 is composed of an oscillator, slope compensation ramp generator, current amplifier, g generator, and a 500mA bipolar output transistor. The oscil- lator generates a 1.2MHz clock. The clock’ ...

Page 6

... MIC2287 External Component Selection The MIC2287 can be used across a wide rage of applications. Series LEDs 6 6 6 6 6.8 H 4.7 H M0510-081104 The table below shows recommended inductor and output capacitor values for various series-LED applications ...

Page 7

... If the LEDs are disconnected from the circuit case an LED fails open, the sense resistor will pull the FB pin to ground. This will cause the MIC2287 to switch with a high duty-cycle, resulting in output overvoltage. This may cause the SW pin voltage to exceed its maximum voltage rating, possibly damaging the IC and the external components ...

Page 8

... MIC2287 6-Series LED Circuit without External Soft-Start TIME (100 s/div.) M0510-081104 6-Series LED Circuit with External Soft-Start 0.22 F OUT 20mA OUT 6 LEDs 8 Micrel 0.22 F OUT 20mA OUT 6 LEDs C = 2200pF 10k TIME (100 s/div.) ...

Page 9

... MIC2287 Package Information August 2004 All Dimensions are in millimeters 5-Pin TSOT (BD5) 8-Pin MLF™ (BML) 9 Micrel M0510-081104 ...

Page 10

... MIC2287 Recommended Land Pattern for MLF™ Lead MICREL, INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA + 1 (408) 944-0800 TEL The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. ...

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