MIC2845A
High Efficiency 6 Channel Linear WLED
Driver with DAM™, Ultra Fast PWM™
Control and Dual Low I
Q
LDOs
General Description
The MIC2845A is a high efficiency White LED (WLED)
driver designed to drive up to six LEDs, greatly extending
battery life for portable display backlighting, keypad
backlighting, and camera flash in mobile devices. The
MIC2845A provides the highest possible efficiency as this
architecture has no switching losses present in traditional
charge pumps or inductive boost circuits. The MIC2845A
provides six linear drivers channels which maintain
constant current for up to six LEDs. It features a typical
dropout of 40mV at 20mA. This allows the LEDs to be
driven directly from the battery eliminating switching
noise/losses present with the use of boost circuitry.
The MIC2845A features Dynamic Average Matching™
(DAM™) which is specifically designed to provide optimum
matching across all WLEDs. The six channels are
matched better than ±1.5% typical, ensuring uniform
display illumination under all conditions. The brightness is
controlled through an Ultra Fast PWM™ Control interface
operating down to less than 1% duty cycle.
The MIC2845A also features two independently enabled
low quiescent current LDOs. Each LDO offers ±3%
accuracy from the nominal voltage over temperature, low
dropout voltage (150mV @ 150mA), and low ground
current under all load conditions (typically 35µA). Both
LDOs can be disabled to draw virtually no current.
The MIC2845A is available in the 14-pin 2.5mm x 2.5mm
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.
Features
WLED Driver
•
•
•
•
•
•
•
•
High Efficiency (no Voltage Boost losses)
Dynamic Average Matching™ (DAM™)
Ultra Fast PWM™ control (200Hz to 500kHz)
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
Very low ground current – Typical 35µA
Stable with 1µF ceramic output capacitor
Dropout of 150mV at 150mA
Thermal shutdown and current limit protection
Available in a 14-pin 2.5mm x 2.5mm Thin MLF
®
package
LDOs
•
•
•
•
•
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 and Ultra Fast PWM are trademarks 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-C
Micrel Inc.
MIC2845A
Typical Application
LCD Display Backlight with 6 WLEDs and Camera Module
High Current Flash Driver
April 2010
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M9999-041210-C
Micrel Inc.
MIC2845A
Ordering Information
Part Number
MIC2845A-MFYMT
MIC2845A-MGYMT
MIC2845A-PGYMT
MIC2845A-PPYMT
MIC2845A-SCYMT
Notes:
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 voltage options.
®
®
Mark Code
(
1)
YNMF
YNMG
YNPG
YNPP
YNSC
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
(
2)
14-Pin 2.5mm x 2.5mm Thin MLF
®
14-Pin 2.5mm x 2.5mm Thin MLF
®
14-Pin 2.5mm x 2.5mm Thin MLF
®
14-Pin 2.5mm x 2.5mm Thin MLF
®
14-Pin 2.5mm x 2.5mm Thin MLF
®
Pin Configuration
LDO1
EN1
D6
D5
VIN
LDO2
EN2
EPAD
D4
GND
D3
RSET
D1
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
END
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 for LED driver. Can be used as a PWM input for dimming of LEDs. 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.
END
April 2010
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M9999-041210-C
Micrel Inc.
MIC2845A
Absolute Maximum Ratings
(1)
Main Input Voltage (V
IN
) .................................. –0.3V to +6V
Enable Input Voltage (V
END
, 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
END
, V
EN1
, V
EN2
) ................ 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
2.5mm x 2.5mm Thin MLF-14L (θ
JA
) .................89°C/W
Electrical Characteristics
WLED Linear Drivers
V
IN
= V
END
= 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
Supply Bias Current
Shutdown Current
(current source leakage)
PWM Dimming
Enable Input Voltage (V
END
)
Enable Input Current
Current Source Delay
(50% levels)
Logic Low
Logic High
V
IH
= 1.2V
Shutdown to On
Standby to On
On to Standby
Current Source Transient Time
(10%-90%)
Stand-by to Shutdown Time
T
RISE
T
FALL
V
END
= 0V
10
1.2
0.01
40
2
0.3
1.3
0.3
24
40
1
80
0.2
V
V
µA
µs
µs
µs
µs
µs
ms
(6)
(5)
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
April 2010
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M9999-041210-C
Micrel Inc.
LDOs
MIC2845A
V
IN
= V
EN1
= V
EN2
= 3.8V, V
END
= 0V, C
OUT1
= C
OUT2
= 1µF, I
OUT1
= I
OUT2
= 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)
Ground Pin Current
Ground Pin Current in Shutdown
Ripple Rejection
Current Limit
Output Voltage Noise
Enable Inputs (EN1, EN2)
Enable Input Voltage
Enable Input Current
Turn-on 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. 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.
Conditions
Variation from nominal V
OUT
Min
–2
–3
Typ
Max
+2
+3
Units
%
%
%/V
mV
mV
µA
µA
dB
mA
µV
RMS
0.02
I
OUT
= 100µA to 150mA
V
OUT
≥
3.0V, I
OUT
= 150mA
V
EN
= 0V
f = 1kHz; C
OUT
= 2.2µF
V
OUT
=0V
Frequency 10Hz to 100kHz
Logic Low
Logic High
V
EN1
= V
EN2
= 1.2V
C
OUT
= 1µF; 90% of V
OUT
1.2
0.01
50
175
7
150
35
0.05
65
300
200
0.3
330
70
1
500
0.2
1
100
V
V
µA
µs
April 2010
5
M9999-041210-C
嵌入式系统
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