MIC4811YMM-TR [MICROCHIP]
LED DISPLAY DRIVER;
| 型号： | MIC4811YMM-TR |
| 厂家： | 
MICROCHIP |
| 描述： | LED DISPLAY DRIVER 驱动 光电二极管 接口集成电路 |
| 文件： | 总12页 (文件大小：610K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MIC4811
High Current 6 Channel Linear WLED
Driver with DAM™ and Ultra Fast
PWM™ Control
General Description
Features
The MIC4811 is a high efficiency linear White LED
(WLED) driver designed to drive up to six high current
WLEDs for signage lighting. The MIC4811 provides the
highest possible efficiency as this architecture has no
switching losses present in traditional charge pumps or
inductive boost circuits. The MIC4811 provides six linear
drivers which maintain constant current for up to six
WLEDs. It features a typical dropout of 100mV at 50mA.
• High Efficiency (no Voltage Boost losses)
• Ultra Fast PWM™ control (200Hz to 500kHz)
• Input voltage range: 3.0V to 5.5V
• LED current range up to 50mA per channel
• Programmable LED current with external resistor
• Dropout of 100mV at 50mA
• Matching better than ±1% (typical)
The MIC4811 features Dynamic Average Matching™
(DAM™) which is specifically designed to provide optimum
matching across all WLEDs. The high accuracy (±1%
typical) current regulated WLED channels ensure uniform
display illumination under all conditions. The brightness is
controlled through an Ultra Fast PWM™ interface
operating down to less than 1% duty cycle.
• Current Accuracy better than ±1% (typical)
• Maintains proper regulation regardless of how many
channels are utilized
• 10-pin MSOP package
Applications
The MIC4811 is available in an 10-pin MSOP 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.
• Billboard displays
• Marquee displays
• Instrument displays
• LCD display modules
____________________________________________________________________________________________________________
Typical Application
High Current Lighting (Six WLEDs)
Ultra Fast PWM, DAM and Dynamic Average Matching are trademark of Micrel, 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
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Micrel Inc.
MIC4811
Ordering Information
Part Number
Mark Code(1)
Junction Temperature Range
Package
MIC4811YMM
4811
–40°C to +125°C
10-Pin MSOP
Pin Configuration
10-Pin MSOP (MM)
(Top View)
Pin Description
Pin Number
Pin Name
VIN
Pin Function
1
2
Voltage Input. Connect at least 2.2µF ceramic capacitor between VIN and GND.
EN
Enable LED drivers. This pin can be used as a PWM input for dimming of WLEDs. Do not leave
floating.
3
RSET
An internal 1.27V reference sets the nominal maximum WLED current. Example, apply a 16.5kΩ
resistor between RSET and GND to set LED current to 50mA at 100% duty cycle.
4
5
GND
D6
Ground.
LED6 driver input. Connect LED anode to VIN and cathode to this pin.
LED5 driver input. Connect LED anode to VIN and cathode to this pin.
LED4 driver input. Connect LED anode to VIN and cathode to this pin.
LED3 driver input. Connect LED anode to VIN and cathode to this pin.
LED2 driver input. Connect LED anode to VIN and cathode to this pin.
LED1 driver input. Connect LED anode to VIN and cathode to this pin.
6
D5
7
D4
8
D3
9
D2
10
D1
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MIC4811
Absolute Maximum Ratings(1)
Operating Ratings(2)
Main Input Voltage (VIN).................................. –0.3V to +6V
Enable Input Voltage (VEN).............................. –0.3V to +6V
LED Driver Voltage (VD1-D6) ............................ –0.3V to +6V
Power Dissipation .....................................Internally Limited
Lead Temperature (soldering, 10sec.)....................... 260°C
Storage Temperature (Ts) .........................–65°C to +150°C
ESD Rating(3)...............................................................1.5kV
Supply Voltage (VIN)..................................... +3.0V to +5.5V
Enable Input Voltage (VEN) .................................... 0V to VIN
LED Driver Voltage (VD1-D6) ................................... 0V to VIN
Junction Temperature (TJ) ........................–40°C to +125°C
Junction Thermal Resistance
MSOP-10L (θJA)............................................130.5°C/W
Electrical Characteristics
VIN = VEN = 5V, RSET = 16.5kΩ; VD1-D6 = 1.2V; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ 125°C; unless noted.
Parameter
Conditions
Min
Typ
50
1
Max
52.5
3.6
Units
mA
%
Current Accuracy(4)
Matching(5)
47.5
Drop-out
Where ILED = 90% of LED current seen at
100
180
mV
VDROPNOM = 1.2V, 100% brightness level
Ground/Supply Bias Current
Shutdown Current
1.7
2.2
1
mA
µA
VEN = 0V
0.01
PWM Dimming
Enable Input Voltage (VEN
)
Logic Low
Logic High
VIH > 1.2V
0.2
V
V
1.2
Enable Input Current
0.01
1
µA
Current Source Delay
(50% levels)
Shutdown to on
Standby to on
On to Standby
40
1
60
µs
µs
µs
0.3
Current Source Transient Time
(10%-90%)
TRISE
TFALL
1
µs
µs
0.3
Stand-by to Shutdown Time
VEN = 0V
10
20
40
ms
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.
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MIC4811
Typical Characteristics
Average Current
vs. Duty Cycle
Single Channel Current
vs. RSET
Single Channel Dropout
vs. LED Current
100
900
800
700
600
500
400
300
200
100
0
1000
100
10
90
80
70
60
50
40
30
20
10
0
1
1
10
100
1000
0
20
40
60
80
100
0
100
200
300
400
500
RSET (kΩ)
LED CURRENT (mA)
DUTY CYCLE (%)
Dropout Voltage
vs. Temperature
Average Current Matching
vs. Temperature
LED Current
vs. Temperature
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
52.0
51.5
51.0
50.5
50.0
49.5
49.0
48.5
48.0
140
120
100
80
LED1
LED5
LED4
LED6
60
LED3
LED2
40
20
RSET = 16.5kꢀ
RSET = 16.5kꢀ
0
-40 -20
0
20 40 60 80 100 120 140
-40 -20
0
20 40 60 80 100 120 140
-40 -20
0
20 40 60 80 100 120 140
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
Peak ILED
vs. Input Voltage
51.0
50.5
50.0
49.5
49.0
48.5
48.0
LED2
LED6
LED5
LED3
LED4
LED1
RSET = 16.5kꢀ
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
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MIC4811
Functional Characteristics
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MIC4811
Functional Diagram
Figure 1. MIC4811 Functional Block Diagram
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MIC4811
RSET
Functional Description
The RSET pin is used to set the peak current of the linear
driver by connecting a RSET resistor to ground. The
average LED current can be calculated by equation (1):
The MIC4811 is a six channel linear WLED driver. The
WLED driver is designed to maintain proper current
regulation with LED current accuracy of 1%, and typical
matching of 1% across the six channels. The WLEDs
are driven independently from the input supply and will
maintain regulation with a dropout of 100mV at 50mA.
The low dropout allows the WLEDs to be driven directly
from the battery voltage and eliminates the need for
large and inefficient charge pumps. The maximum
WLED current for each channel is set by the external
RSET resistor. Dimming is controlled by applying a PWM
signal to the END pin. The MIC4811 accommodates a
wide PWM frequency range as outlined in the application
information section.
RSET [kꢀ] = ( 820 / ILED [mA] ) + 0.139
(1)
A plot of ILED versus RSET is shown in Figure 2.
Peak LED Current
vs. RSET
1000
100
10
1
Block Diagram
As shown in Figure 1, the MIC4811 consists of six
current mirrors set to copy a master current determined
by the RSET resistor. The linear drivers have a
designated control block for enabling and dimming the
WLEDs.
1
10
100
1000
RSET (kΩ)
VIN
The input supply (VIN) provides power to the linear
drivers and the control circuitry. The VIN operating range
is 3V to 5.5V. A bypass capacitor of 2.2µF should be
placed close to input (VIN) pin and the ground (GND)
pin. Refer to the layout recommendations section for
details on placing the input capacitor (C1).
Figure 2. Peak LED Current vs. RSET
D1-D6
The D1 through D6 pins are the linear driver inputs for
WLED 1 through 6, respectively. Connect the anodes of
the WLEDs to VIN and each cathode of the WLEDs to D1
through D6. When operating with less than six WLEDs,
leave the unused D pins unconnected. The linear drivers
are extremely versatile in that they may be used in any
combinations, for example D1 thru D6 leaving D5
unconnected or paralleled for higher current
applications.
EN
The EN pin is equivalent to the enable pin for the linear
drivers on the MIC4811. It can also be used for dimming
using a PWM signal. See the PWM Dimming Interface in
the Application Information section for details. Pulling the
END low for more than 20ms puts the MIC4811 into a
low Iq sleep mode. The EN pin cannot be left floating; a
floating enable pin may cause an indeterminate state on the
outputs. The first pulse on the EN pin must be equal or
greater to 60μs to wake the part up in a known state. This
equates to 3.3kHz PWM signal at equal or greater than 50%
duty cycle. Higher PWM frequencies may be used but the
first pulse must be equal or greater than 60μs.
GND
The ground pin is the ground path for the linear drivers.
The current loop for the ground should be as small as
possible. The ground of the input capacitor should be
routed with low impedance traces to the GND pin and
made as short as possible. Refer to the layout
recommendations for more details.
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Micrel Inc.
MIC4811
Application Information
Dynamic Average Matching (DAM™)
The Dynamic average matching architecture multiplexes
four voltage references to provide highly accurate LED
current and channel matching. The MIC4811 achieves
industry leading LED channel matching of 1% across the
entire dimming range.
Ultra Fast PWM™ Dimming Interface
The MIC4811 supports a wide range of PWM control
signal frequencies from 200Hz to 500kHz. This
extremely wide range of control provides ultimate
flexibility for handheld applications using high frequency
PWM control signals.
WLED dimming is achieved by pulse width modulating
the linear drivers which are controlled by a PWM signal
to the END pin. For PWM frequencies between 200Hz –
20kHz the MIC4811 supports a duty cycle range from
1% to 100%, see Figure3. The MIC4811 incorporates an
internal shutdown delay to ensure that the internal
control circuitry remains active during PWM dimming.
This feature prevents the possibility of backlight
flickering when using low frequency PWM control
signals. The MIC4811 also supports Ultra Fast PWM™
frequencies from 20kHz to 500kHz. Due to input signal
propagation delay, PWM frequencies above 20kHz have
a non-linear relationship between the duty cycle and the
average LED current, see Figures 4 and 5. Figures 6
through 10 show the WLED current response when a
Figure 4. Channel Current Response to PWM Control
Signal Frequencies from 50kHz to 500kHz
PWM signal is applied to the END pin (1)
.
(1)
From the low Iq sleep mode higher PWM frequencies may require a
logic high enable signal for 60μs to first enable the MIC4811 prior to
PWM dimming.
Figure 5. Minimum Duty Cycle
for Varying PWM Frequency
Figure 3. Average Current per LED Dimming
by Changing PWM Duty Cycle for PWM Frequencies
up to 20kHz
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MIC4811
Figure 6. PWM Signal at 1% Duty Cycle (Iavg = 0.5mA)
Figure 9. PWM Signal at 80% Duty Cycle (Iavg = 40mA)
Figure 7. PWM Signal at 20% Duty Cycle (Iavg =10 mA)
Figure 10. PWM Signal at 100% Duty Cycle (Iavg = 50mA)
Input Capacitor
The MIC4811 is a high-performance, high bandwidth
device. Stability can be maintained using a ceramic input
capacitor of 2.2µF. Low-ESR ceramic capacitors provide
optimal performance at a minimum amount of space.
X5R or X7R dielectrics are recommended for the input
capacitor. Y5V dielectrics lose most of their capacitance
over temperature and are therefore, not recommended.
Figure 8. PWM Signal at 50% Duty Cycle (Iavg = 25mA)
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Micrel Inc.
MIC4811
MIC4811 Typical Application Circuit
Bill of Materials
Item
Part Number
C1608X5R0J225K
06036D225KAT2A
GRM188R60J225KE19D
VJ0603G225KXYAT
OVS5WBCR4
Manufacturer
TDK(1)
Description
Qty.
AVX(2)
Murata(3)
Vishay(4)
C1
Ceramic Capacitor, 2.2µF, 6.3V, X5R, Size 0603
1
OPTEK Technology, Inc(5)
D1 – D6
R1
WLED
6
1
1
CRCW060316K55F5EA
CRCW06032003FKEA
Vishay(4)
Vishay(4)
Resistor, 16.5k, 1%, 1/16W, Size 0603
Resistor, 200k, 1%, 1/16W, Size 0603
R2
High Current 6 Channel Linear WLED Driver
with DAM™ and Ultra Fast PWM™ Control
U1
MIC4811YMM
Micrel, Inc.(6)
1
Notes:
1. TDK: www.tdk.com
2. AVX: www.avx.com
3. Murata: www.murata.com
4. Vishay: www.vishay.com
5. OPTEK: www.optekinc.com
6. Micrel, Inc.: www.micrel.com
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Micrel Inc.
MIC4811
PCB Layout Recommendations
Top Layer
Bottom Layer
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Micrel Inc.
MIC4811
Package Information
10-Pin MSOP (MM)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This
information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry,
specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual
property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability
whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties
relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product
can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical
implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A
Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully
indemnify Micrel for any damages resulting from such use or sale.
© 2010 Micrel, Incorporated.
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相关型号：
MIC4812_1104
High Current 6 Channel Linear WLED Driver with DAM⢠and Ultra Fast PWM⢠Control
MICREL
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