MIC2289-34BML TR Micrel Inc, MIC2289-34BML TR Datasheet - Page 5

• Manufacturer Part Number: MIC2289-34BML TR
• Description: IC LED DRIVER WHITE BCKLGT 8-MLF
• Manufacturer: Micrel Inc
• Type: Backlight, White LEDr

Specifications of MIC2289-34BML TR

• Constant Current: Yes
• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 1
• Internal Driver: Yes
• Type - Primary: Backlight, Flash/Torch
• Type - Secondary: White LED
• Frequency: 1.05MHz ~ 1.35MHz
• Voltage - Supply: 2.5 V ~ 10 V
• Mounting Type: Surface Mount
• Package / Case: 8-MLF®, QFN
• Operating Temperature: -40°C ~ 125°C
• Current - Output / Channel: 20mA
• Internal Switch(s): Yes
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Voltage - Output: -
• Efficiency: -
• Other names: MIC2289-34BMLTR; MIC2289-34BMLTR

Functional Diagram
Functional Description
The MIC2289 is a constant frequency, PWM current
mode boost regulator. The block diagram is shown
above. The MIC2289 is composed of an oscillator, slope
compensation ramp generator, current amplifier, g
amplifier, PWM generator, 500mA bipolar output
transistor, and Schottky rectifier diode. The oscillator
generates a 1.2MHz clock. The clock’s two functions are
to trigger the PWM generator that turns on the output
transistor and to reset the slope compensation ramp
generator. The current amplifier is used to measure the
switch current by amplifying the voltage signal from the
internal sense resistor. The output of the current
amplifier is summed with the output of the slope
compensation ramp generator. This summed current-
loop signal is fed to one of the inputs of the PWM
generator.
Micrel, Inc.
July 2007
V
VIN
REF
95mV
FB
OVP
g
m
Oscillator
1.2MHz
MIC2289 Block Diagram
m
error
5
Generator
Generator
The g
the external sense resistor and amplifies the error
between the detected signal and the 95mV reference
voltage. The output of the gm error amplifier provides the
voltage-loop signal that is fed to the other input of the
PWM generator. When the current-loop signal exceeds
the voltage-loop signal, the PWM generator turns off the
bipolar output transistor. The next clock period initiates
the next switching cycle, maintaining the constant
frequency current-mode PWM control. The LED is set by
the feedback resistor:
The Enable pin shuts down the output switching and
disables control circuitry to reduce input current-to-
leakage levels. Enable pin input current is zero at zero
volts.
Ramp
PWM
EN
S
m
error amplifier measures the LED current through
I
LED
=
95mW
R
FB
OUT
SW
GND
M9999-071007
MIC2289