MIC2846A
High Efficiency 6 Channel Linear WLED
Driver with DAM™, Digital Control and Dual
Low I
Q
LDOs
General Description
The MIC2846A is a high efficiency White LED (WLED)
driver featuring two low quiescent current LDOs. It is
designed to drive up to six LEDs and greatly extend
battery life for portable display backlighting and keypad
backlighting in mobile devices. The MIC2846A architecture
provides the highest possible efficiency by eliminating
switching losses present in traditional charge pumps or
inductive boost circuits. With a typical dropout of 40mV at
20mA, the MIC2846A allows the LEDs to be driven directly
from the battery eliminating switching noise and losses
present with the use of boost circuitry.
The MIC2846A features Dynamic Averaged Matching™
(DAM™) which is specifically designed to get the optimum
matching despite process variations. This ensures a
typical matching of ±1.5% between all six LED channels.
The LED brightness is preset by an external resistor and
can be dimmed using a single-wire digital control. The
digital interface takes commands from digital programming
pulses to change the brightness in a logarithmic scale
similar to the eye’s perception of brightness. The single-
wire digital brightness control is divided into two modes of
operation; full brightness mode or battery saving mode for
a total of 49 brightness steps.
The MIC2846A also features two independently enabled
low quiescent current LDOs. Each LDO offers ±3%
accuracy over temperature, low dropout voltage (150mV
@ 150mA), and low ground current under all load
conditions (typically 35µA). Both LDOs can be turned off to
draw virtually no current.
The MIC2846A is available in the 2.5mm x 2.5mm 14-pin
Thin MLF
®
leadless package with a junction temperature
range of -40°C to +125°C
Datasheet and support documentation can be found on
Micrel’s web site at: www.micrel.com.
Features
WLED Driver
•
High Efficiency (no Voltage Boost losses)
•
Dynamic Average Matching™ (DAM™)
•
Single wire digital control
•
Input voltage range: 3.0V to 5.5V
•
Dropout of 40mV at 20mA
•
Matching better than ±1.5% (typical)
•
Current accuracy better than ±1.5% (typical)
•
Maintains proper regulation regardless of how many
channels are utilized
LDOs
•
Very low ground current – Typical 35µA
•
Stable with 1µF ceramic output capacitor
•
Dropout at 150mV at 150mA
•
Thermal shutdown and current limit protection
•
Available in a 2.5mm x 2.5mm 14-pin Thin MLF
®
package
Applications
•
Mobile handsets
•
LCD Handset backlighting
•
Handset keypad backlighting
•
Digital cameras
•
Portable media/MP3 players
•
Portable navigation devices (GPS)
•
Portable applications
DAM, Dynamic Average Matching is a trademark of Micrel, Inc.
MLF and
MicroLeadFrame
are registered trademark 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
April 2010
M9999-041210-D
Micrel Inc.
MIC2846A
Typical Application
Digital
LCD Display Backlight with 6 WLEDs and Camera Module
6
Digital
High Current Flash Driver
April 2010
2
M9999-041210-D
Micrel Inc.
MIC2846A
Ordering Information
(1,2,3)
Part Number
MIC2846A-MFYMT
MIC2846A-MGYMT
MIC2846A-PGYMT
MIC2846A-PPYMT
MIC2846A-SCYMT
Note:
®
®
Mark
Code
YPMF
YPMG
YPPG
YPPP
YPSC
LDO1
VOUT
2.8V
2.8V
3.0V
3.0V
3.3V
LDO2
VOUT
1.5V
1.8V
1.8V
3.0V
1.0V
Temperature Range
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
Package
14-Pin 2.5mm x 2.5mm TMLF
®
14-Pin 2.5mm x 2.5mm TMLF
®
14-Pin 2.5mm x 2.5mm TMLF
®
14-Pin 2.5mm x 2.5mm TMLF
®
14-Pin 2.5mm x 2.5mm TMLF
®
1. Thin MLF
▲
= Pin 1 identifier.
2. Thin MLF is a GREEN RoHS-compliant package. Lead finish is NiPdAu. Mold compound is halogen free.
3. Contact Micrel for other output voltages.
Pin Configuration
14-Pin 2.5mm x 2.5mm Thin MLF
®
(MT) (Top View)
Pin Description
Pin Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
EPAD
Pin Name
VIN
LDO2
EN2
DC
RSET
D1
D2
D3
GND
D4
D5
D6
EN1
LDO1
HS PAD
Pin Function
Voltage Input. Connect at least 1µF ceramic capacitor between VIN and GND.
Output of LDO2. Connect at least 1µF ceramic output capacitor.
Enable Input for LDO2. Active High Input. Logic High = On; Logic Low = Off; Do not leave floating.
Enable input for LED driver. Can be used for dimming using the digital control interface. See Digital
Dimming Interface for details. Do not leave floating.
An internal 1.27V reference sets the nominal maximum LED current. Example, apply a 20.5kΩ
resistor between RSET and GND to set LED current to 20mA at 100% duty cycle.
LED1 driver. Connect LED anode to VIN and cathode to this pin.
LED2 driver. Connect LED anode to VIN and cathode to this pin.
LED3 driver. Connect LED anode to VIN and cathode to this pin.
Ground.
LED4 driver. Connect LED anode to VIN and cathode to this pin.
LED5 driver. Connect LED anode to VIN and cathode to this pin.
LED6 driver. Connect LED anode to VIN and cathode to this pin.
Enable Input for LDO1. Active High Input. Logic High = On; Logic Low = Off; Do not leave floating.
Output of LDO1. Connect at least 1µF ceramic output capacitor.
Heat sink pad. Not internally connected. Connect to ground.
April 2010
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M9999-041210-D
Micrel Inc.
MIC2846A
Absolute Maximum Ratings
(1)
Main Input Voltage (V
IN
) ................................... -0.3V to +6V
Enable Input Voltage (V
DC
, V
EN1
, V
EN2
) ............ -0.3V to +6V
LED Driver Voltage (V
D1-D6
).............................. -0.3V to +6V
Power Dissipation ................................. Internally Limited
(3)
Lead Temperature (soldering, 10sec.)....................... 260°C
Storage Temperature (T
s
) ..........................-65°C to +150°C
ESD Rating
(4)
................................................. ESD Sensitive
Operating Ratings
(2)
Supply Voltage (V
IN
).................................. +3.0V to +5.5V
Enable Input Voltage (V
DC
, V
EN1
, V
EN2
) .............. 0V to V
IN
LED Driver Voltage (V
D1-6
) ................................. 0V to V
IN
Junction Temperature (T
J
) .....................–40°C to +125°C
Junction Thermal Resistance
2.5mm x 2.5mm Thin MLF-14L (θ
JA
) ..............89°C/W
Electrical Characteristics
Linear WLED Drivers
V
IN
= V
DC
= 3.8V, V
EN1
= V
EN2
= 0V, 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
Matching
Drop-out
Ground/Supply Bias Current
Shutdown Current
(current source leakage)
(6)
(5)
Conditions
Min
Typ
1.5
1.5
Max
Units
%
%
Where I
LED
= 90% of LED current seen at
V
DROPNOM
= 0.6V, 100% brightness level
I
LED
= 20mA
V
DC
= 0V for more than 1260µs
40
1.4
0.01
80
1.8
1
mV
mA
µA
Digital Dimming
V
DC
Input Voltage (V
DC
)
V
DC
Enable Input Current
t
SHUTDOWN
t
MODE_UP
t
MODE_DOWN
t
PROG_HIGH
, t
PROG_LOW
t
DELAY
t
PROG_SETUP
t
START_UP
Logic Low
Logic High
V
DC
= 1.2V
Time DC pin is low to shutdown the device
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 time starting when DC is first pulled high until
LEDs start up
1260
100
420
2
100
5
140
75
160
500
32
1.2
0.01
1
0.2
V
V
µA
µs
µs
µs
µs
µs
µs
µs
LDOs
V
IN
= V
EN1
= V
EN2
= 3.8V, V
DC
= 0V; C
OUT1
= C
OUT2
= 1μF, I
OUT1
= I
OUT1
= 100μA; T
J
= 25°C,
bold
values indicate –40°C
≤
T
J
≤125°C;
unless noted.
Parameter
Output Voltage Accuracy
V
IN
Line Regulation
Load Regulation
Dropout Voltage
(7)
Conditions
Variation from nominal V
OUT
Min
-2
-3
Typ
Max
+2
+3
Units
%
%
%/V
mV
mV
µA
µA
0.02
I
OUT
= 100μA to 150mA
V
OUT
>= 3.0V; I
OUT
= 150mA
V
EN
= 0V
7
150
35
0.05
0.3
330
70
1.0
Ground Pin Current
Ground Pin Current in Shutdown
April 2010
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M9999-041210-D
Micrel Inc.
LDOs (continued)
Parameter
Ripple Rejection
Current Limit
Output Voltage Noise
Enable Inputs (EN1,2)
Enable Input Voltage
Enable Input Current
Turn-on Time
Notes:
MIC2846A
Conditions
f = 1kHz; C
OUT
= 2.2μF
V
OUT
= 0V
Frequency 10Hz to 100kHz
Logic Low
Logic High
V
EN1
= V
EN1
= 1.2V
C
OUT
= 1µF; 90% of V
OUT
Min
175
Typ
65
300
200
Max
500
Units
dB
mA
µV
RMS
0.2
1.2
0.01
50
1
100
V
V
µA
µs
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. The maximum allowable power dissipation of any T
A
(ambient temperature) is P
D(max)
= (T
J(max)
– T
A
) /
θ
JA
. Exceeding the maximum allowable power
dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown (150°C).
4. Devices are ESD sensitive. Handling precautions recommended. Human Body Model (HBM), 1.5kΩ in series with 100pF.
5. As determined by average current of all channels in use and all channels loaded.
6. The current through each channel meets the stated limits from the average current of all channels.
7. Dropout voltage is defined as the input-output differential at which the output voltage drops 2% below its nominal value measured at V
IN
= V
OUT
+ 1V.
April 2010
5
M9999-041210-D
嵌入式系统
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