MIC2841A
High Efficiency 4 Channel Linear WLED
Driver with DAM™ and Ultra Fast
PWM™ Control
General Description
Features
The MIC2841A is a high efficiency White LED (WLED)
•
High Efficiency (no Voltage Boost losses)
driver designed to drive up to four WLEDs, greatly
•
Dynamic Average Matching™ (DAM™)
extending battery life for portable display backlighting,
•
Ultra Fast PWM™ control (200Hz to 500kHz)
keypad backlighting and camera flash in mobile devices.
•
Input voltage range: 3.0V to 5.5V
The MIC2841A provides the highest possible efficiency as
•
Dropout of 40mV at 20mA
this architecture has no switching losses present in
traditional charge pumps or inductive boost circuits. The
•
Matching better than ±1.5% (typical)
MIC2841A provides four linear driver channels which
•
Current accuracy better than ±1.5% (typical)
maintain constant current for up to four WLEDs. It features
•
Maintains proper regulation regardless of how many
a typical dropout of 40mV at 20mA. This allows the
channels are utilized
WLEDs to be driven directly from the battery eliminating
•
Available in a 10-pin 2mm x 2mm Thin MLF
®
package
switching noise/losses present with the use of boost
circuitry.
Applications
The MIC2841A features Dynamic Average Matching™
(DAM™) which is specifically designed to provide optimum
•
Mobile handsets
matching across all WLEDs. The four channels are
•
Handset LCD backlighting
matched better than ±1.5% typical, ensuring uniform
•
Handset keypad backlighting
display illumination under all conditions. The brightness is
controlled through an Ultra Fast PWM™ interface
•
Flash driver
operating down to less than 1% duty cycle.
•
Digital cameras
The MIC2841A is available in the 2mm x 2mm 10-pin Thin
•
Portable media/MP3 players
MLF
®
leadless package with a junction temperature range
•
Portable navigation devices (GPS)
of -40°C to +125°C.
•
Portable applications
Datasheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
____________________________________________________________________________________________________________
Typical Application
U1 MIC2841AYMT
U1 MIC2841AYMT
V
IN
C1
R
SET
Low
Dropout
Linear
Driver
PWM
Control
V
IN
V
IN
C1
R
SET
END
Low
Dropout
Linear
Driver
PWM
Control
END
GND
LCD Display Backlight with Four WLEDs
Ultra Fast PWM, DAM and Dynamic Average Matching are trademarks of Micrel, Inc.
MLF and
MicroLeadFrame
are registered trademark Amkor Technology Inc.
High Current Flash Driver
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (
408
) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
June 2009
M9999-062909-C
Micrel Inc.
MIC2841A
Ordering Information
Part Number
MIC2841AYMT
Note:
1. Thin MLF
▲
= Pin 1 identifier.
2. Thin MLF is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is halogen free.
®
®
Mark Code
(1)
Q1Y
Temperature Range
–40°C to +125°C
Package
(2)
10-Pin 2mm x 2mm Thin MLF
®
Pin Configuration
VIN
END
RSET
GND
N/C
1
2
3
4
5
10 D1
9
8
7
6
D2
D3
D4
N/C
10-Pin 2mm x 2mm Thin MLF
®
(MT)
(Top View)
Pin Description
Pin Number
1
2
3
4
5
6
7
8
9
10
EPAD
Pin Name
VIN
END
RSET
GND
NC
NC
D4
D3
D2
D1
HS PAD
Pin Function
Voltage Input. Connect at least 1µF ceramic capacitor between VIN and GND.
Enable LED drivers. This pin can be used as a PWM input for dimming of WLEDs. Do not leave
floating.
An internal 1.27V reference sets the nominal maximum WLED current. Example, apply a 20.5kΩ
resistor between RSET and GND to set LED current to 20mA at 100% duty cycle.
Ground.
No Connect. This pin is not connected internally.
No Connect. This pin is not connected internally.
LED4 driver. Connect LED anode to VIN and cathode to this pin.
LED3 driver. Connect LED anode to VIN and cathode to this pin.
LED2 driver. Connect LED anode to VIN and cathode to this pin.
LED1 driver. Connect LED anode to VIN and cathode to this pin.
Heat sink pad. Not internally connected. Connect to ground.
June 2009
2
M9999-062909-C
Micrel Inc.
MIC2841A
Absolute Maximum Ratings
(1)
Main Input Voltage (V
IN
) .................................. –0.3V to +6V
Enable Input Voltage (V
END
) ............................ –0.3V to +6V
LED Driver Voltage (V
D1-D4
) ............................ –0.3V to +6V
Power Dissipation .....................................Internally Limited
Lead Temperature (soldering, 10sec.)....................... 260°C
Storage Temperature (T
s
) .........................–65°C to +150°C
ESD Rating
(3)
................................................. ESD Sensitive
Operating Ratings
(2)
Supply Voltage (V
IN
)..................................... +3.0V to +5.5V
Enable Input Voltage (V
END
) .................................. 0V to V
IN
LED Driver Voltage (V
D1-D4
) ................................... 0V to V
IN
Junction Temperature (T
J
) ........................ –40°C to +125°C
Junction Thermal Resistance
2mm x 2mm Thin MLF
®
(θ
JA
).............................90°C/W
Electrical Characteristics
V
IN
= V
END
= 3.8V, R
SET
= 20.5kΩ; V
D1-D4
= 0.6V; T
J
= 25°C,
bold
values indicate –40°C
≤
T
J
≤
125°C; unless noted.
Parameter
Current Accuracy
Matching
Drop-out
Ground/Supply Bias Current
Shutdown Current
(current source leakage)
PWM Dimming
Enable Input Voltage (V
END
)
Enable Input Current
Current Source Delay
(50% levels)
Current Source Transient Time
(10%-90%)
Stand-by to Shutdown Time
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5kΩ in series with 100pF.
4. As determined by average current of all channels in use and all channels loaded.
5. The current through each LED meets the stated limits from the average current of all LEDs.
(5)
(4)
Conditions
Min
Typ
1.5
1.5
Max
3.6
80
1.8
1
Units
%
%
mV
mA
µA
Where I
LED
= 90% of LED current seen at
V
DROPNOM
= 0.6V, 100% brightness level
I
LED
= 20mA
V
END
= 0V
40
1.4
0.01
Logic Low
Logic High
V
IH
> 1.2V
Shutdown to on
Standby to on
On to standby
T
RISE
T
FALL
V
END
= 0V
10
1.2
0.01
40
2
0.3
1
0.3
24
0.2
1
80
V
V
µA
µs
µs
µs
µs
µs
40
ms
June 2009
3
M9999-062909-C
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