MIC2844A
High Efficiency 6 Channel WLED Driver
with DAM™ and Single Wire Digital Control
General Description
Features
The MIC2844A is a high efficiency linear White LED (WLED)
•
High Efficiency (no Voltage Boost losses)
driver designed to drive up to six WLEDs, greatly extending
•
Dynamic Average Matching™ (DAM™)
battery life for portable display backlighting keypad
•
Single wire digital control
backlighting, and camera flash in mobile devices. The
•
Input voltage range: 3.0V to 5.5V
MIC2844A provides the highest possible efficiency as this
•
Dropout of 40mV at 20mA
architecture has no switching losses present in traditional
charge pumps or inductive boost circuits. The MIC2844A
•
Matching better than ±1.5% (typical)
provides six linear drivers which maintain constant current for
•
Current accuracy better than ±1.5% (typical)
up to six WLEDs. It features a typical dropout of 40mV at
•
Maintains proper regulation regardless of how many
20mA. This allows the WLEDs to be driven directly from the
channels are utilized
battery eliminating switching noise/losses present with the
•
Available in a 10-pin 2mm x 2mm Thin MLF
®
package
use of boost circuitry.
The MIC2844A features Dynamic Average Matching™
Applications
(DAM™) which is specifically designed to provide optimum
matching across all WLEDs. The six channels are matched
•
Mobile handsets
better than ±1.5% typical, ensuring uniform display
•
Handset LCD backlighting
illumination under all conditions. The LED brightness is preset
•
Handset keypad backlighting
by an external resistor and can be dimmed using a single-
wire digital control. The digital interface takes commands
•
Camera flash (see MIC2843A datasheet)
from digital programming pulses to change the brightness in
•
Digital cameras
a logarithmic scale similar to the eye’s perception of
•
Portable media/MP3 players
brightness. The single-wire digital brightness control is
divided into two modes of operation; full brightness mode, or
•
Portable navigation devices (GPS)
battery saving mode for a total of 49 brightness steps.
•
Portable applications
The MIC2844A is available in the 10-pin 2mm x 2mm Thin
MLF
®
leadless package with a junction temperature range of
-40°C to +125°C.
Datasheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
____________________________________________________________________________________________________________
Typical Application
U1 MIC2844AYMT
U1 MIC2844AYMT
VIN
V
IN
Low
Dropout
Linear
Driver
Digital
Control
C1
RSET
C1
V
IN
R
SET
Low
Dropout
Linear
Driver
Digital
Control
DC
DC
LCD Display Backlight with Six WLEDs
DAM and Dynamic Average Matching is a trademark 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
August 2009
M9999-080309-D
Micrel Inc.
MIC2844A
Ordering Information
Part Number
MIC2844AYMT
Note:
1.
2.
Thin MLF
®
®
Mark Code
(1)
T4Y
= Pin 1 identifier.
Temperature Range
–40°C to +125°C
Package
(2)
10-Pin 2mm x 2mm Thin MLF
®
Thin MLF is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is halogen free.
Pin Configuration
VIN
DC
RSET
GND
D6
1
2
3
4
5
10 D1
9
8
7
6
D2
D3
D4
D5
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
DC
RSET
GND
D6
D5
D4
D3
D2
D1
HS PAD
Pin Function
Voltage Input. Connect at least 1µF ceramic capacitor between VIN and GND.
Digital control input for linear WLED driver. See Digital Dimming Interface. 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.
LED6 driver. Connect LED anode to VIN and cathode to this pin.
LED5 driver. Connect LED anode to VIN and cathode to this pin.
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.
August 2009
2
M9999-080309-D
Micrel Inc.
MIC2844A
Absolute Maximum Ratings
(1)
Main Input Voltage (V
IN
) .................................. –0.3V to +6V
Enable Input Voltage (V
DC
).............................. –0.3V to +6V
LED Driver Voltage (V
D1-D6
) ............................ –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
DC
) .................................... 0V to V
IN
LED Driver Voltage (V
D1-D6
) ................................... 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
DC
= 3.8V, R
SET
= 20.5kΩ; V
D1-D6
= 0.6V; T
J
= 25°C,
bold
values indicate –40°C
≤
T
J
≤
125°C; unless noted.
Parameter
Current Accuracy
(4)
Matching
(5)
Drop-out
Ground/Supply Bias Current
Shutdown Current
(current source leakage)
Digital Dimming
DC Input Voltage (V
DC
)
Enable Input Current
t
SHUTDOWN
t
MODE_UP
t
MODE_DOWN
t
PROG_HIGH, tPROG_LOW
t
DELAY
t
PROG_SETUP
t
START_UP
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.
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
DC
= 0V > 1260µs
40
1.4
0.01
Logic Low
Logic High
V
DC
= 1.2V
Time DC pin is low to put into shutdown
Time DC pin is low to change to Count Up Mode
Time DC pin is low to change to Count Down Mode
Time for valid edge count; Ignored if outside limit range
Time DC pin must remain high before a mode change
can occur
First down edge must occur in this window during
presetting brightness
Delay from DC is high to start up
1260
100
420
2
100
5
140
1.2
0.01
0.2
1
160
500
32
V
V
µA
µs
µs
µs
µs
µs
75
µs
µs
August 2009
3
M9999-080309-D
京公网安备 11010802033920号
EEWORLD
