MIC4802YME-TR [MICROCHIP]
LED DISPLAY DRIVER;
| 型号： | MIC4802YME-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：534K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MIC4802
High Efficiency 800mA Single Channel
Linear WLED Driver with
Ultra Fast PWM™ Control
General Description
Features
The MIC4802 is a high efficiency White LED (WLED)
driver designed to drive a single LED up to 800mA. The
MIC4802 constant current driver is designed to drive high
power LED’s in various lighting applications. The MIC4802
provides the highest possible efficiency as this architecture
has no switching losses present in traditional charge
pumps or inductive boost circuits. It features a typical
dropout of 280mV at 800mA. This allows the LEDs to be
driven directly from the voltage source eliminating
switching noise/losses present with the use of boost
circuitry. The high accuracy (±1% Typical) current
regulated WLED channel ensures 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.
• High Efficiency (no Voltage Boost losses)
• Ultra Fast PWM™ control (200Hz to 500kHz)
• Input voltage range: 3.0V to 5.5V
• Dropout of 280mV at 800mA
• Programmable LED current with external resistor
• Current accuracy of ±1% typical
Applications
• Bill board displays
• Marquee displays
• Instrument displays
• Architectural lighting
The MIC4802 is available in the 8-pin SOIC Epad 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
High Current Lighting Schematic
Ultra Fast PWM is a 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
M9999-013111-B
January 2011
Micrel Inc.
MIC4802
Ordering Information
Part Number
Temperature Range
Package
MIC4802YME
–40°C to +125°C
8-Pin EPAD SOIC
Pin Configuration
8-Pin Epad SOIC (ME)
(Top View)
Pin Description
Pin Number
Pin Name
VIN
Pin Function
Voltage Input. Connect at least 2.2µF ceramic capacitor between VIN and GND.
1
2
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 6.19kΩ
resistor between RSET and GND to set LED current to 830mA at 100% duty cycle.
4
5
GND
D1
Ground.
LED1 driver input. Connect LED anode to VIN and cathode to this pin. All D1 pins must be
connected to the LED.
6
D1
D1
LED1 driver input. Connect LED anode to VIN and cathode to this pin. All D1 pins must be
connected to the LED.
7
8
LED1 driver input. Connect LED anode to VIN and cathode to this pin. All D1 pins must be
connected to the LED.
D1
LED1 driver input. Connect LED anode to VIN and cathode to this pin. All D1 pins must be
connected to the LED.
EPAD
HS PAD
Heat sink pad. Not internally connected. Connect to ground.
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Micrel Inc.
MIC4802
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) ................................ –0.3V to +6V
Power Dissipation .....................................Internally Limited
Lead Temperature (soldering, 10sec.)....................... 260°C
Storage Temperature (Ts) .........................–65°C to +150°C
Supply Voltage (VIN)..................................... +3.0V to +5.5V
Enable Input Voltage (VEN) .................................... 0V to VIN
LED Driver Voltage (VD1) ....................................... 0V to VIN
Junction Temperature (TJ) ........................–40°C to +125°C
Junction Thermal Resistance
EPAD SOIC-8L (θJA)..........................................41°C/W
Electrical Characteristics
VIN = VEN = 5V, RSET = 6.19kΩ; VD1 = 1.2V; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ 125°C; unless noted.
Parameter
Conditions
Min
Typ
Max
Units
Current Accuracy(3)
747
830
913
mA
Drop-out
Where ILED = 90% of LED current seen at
VDROPNOM = 1.2V, 100% brightness level
280
500
mV
Ground/Supply Bias Current
Shutdown Current
IOUT = 830mA
VEN = 0V
4.1
5.7
1
mA
µA
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
2
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. As determined by average current based on RSET resistance.
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Micrel Inc.
MIC4802
Typical Characteristics
Dropout Voltage
vs. LED Current
LED Battery Voltage
vs. LED Current
LED Current
vs. LED Anode Voltage
500
450
400
350
300
250
200
150
100
50
1.4
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
VIN = 5.5V
V
IN = 5.5V
IN = 3.5V
IN = 3.0V
1.2
1
VIN = 3.5V
VIN = 3.0V
V
0.8
0.6
0.4
0.2
0
V
VIN = 5V
0
5.5
5
4.5
4
3.5
3
2.5
5.5
5
4.5
4
3.5
3
2.5
2.5
100
0
200 400 600 800 1000 1200 1400
LED ANODE VOLTAGE (V)
LED BATTERY VOLTAGE (V)
LED CURRENT (mA)
Peak LED Current
vs. RSET
Supply Bias Current
vs. LED Anode Voltage
LED Current
vs. PWM Duty Cycle
10000
1000
100
10
900
800
700
600
500
400
300
200
100
0
8
7
6
5
4
3
2
1
0
VIN = 5V
VIN = 5.5V
fPWM = 1kHz
fPWM = 5kHz
VIN = 3.5V
VIN = 2.5V
fPWM = 10kHz
RSET = 4.64kΩ
3.5
1
5.5
5
4.5
4
3
0
20
40
60
80
100
1
10
100
1000
10000
LED BATTERY VOLTAGE (V)
RSET (kΩ)
DUTY CYCLE (%)
RSET Voltage
vs. LED Current
LED Current
vs. PWM Duty Cycle
Typical ILED vs. VLED
2
1.8
1.6
1.4
1.2
1
1.4
1.38
1.36
1.34
1.32
1.3
900
800
700
600
500
400
300
200
100
0
VIN = 5.0V
fPWM = 20kHz
fPWM = 100kHz
fPWM = 200kHz
0.8
0.6
0.4
0.2
0
1.28
1.26
fPWM = 500kHz
VIN = 5V
1.24
0
0
20
40
60
80
2.4
2.6
2.8
3
3.2
3.4
3.6
200 400 600 800 1000 1200 1400
DUTY CYCLE (%)
LED FORWARD VOLTAGE (V)
LED CURRENT (mA)
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Micrel Inc.
MIC4802
Functional Characteristics
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Micrel Inc.
MIC4802
Functional Diagram
Figure 1. MIC4802 Functional Block Diagram
Block Diagram
Functional Description
As shown in Figure 1, the MIC4802 consists of current
mirrors set to copy a master current determined by RSET
The linear LED drivers have a designated control block
for enabling and dimming of the LEDs. The MIC4802
dimming is controlled by the Ultra Fast PWMTM control
block that receives PWM signals for dimming.
The MIC4802 is a single channel linear LED driver with a
maximum 800mA current capability. The LED driver is
designed to maintain proper current regulation with LED
current accuracy of ±10%. The dropout is 280mV at
800mA. The low dropout of the linear drivers allows the
LEDs to be driven directly from the battery voltage and
eliminates the need for boost or large and inefficient
charge pumps. The maximum LED current for each
channel is set via an external resistor. Dimming is
controlled by applying a PWM signal to the EN pin. The
MIC4802 accommodates a wide PWM frequency range
as outlined in the application information section.
.
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Micrel Inc.
VIN
MIC4802
Peak LED Current
vs. RSET
The input supply (VIN) provides power to the linear LED
drivers and the control circuitry. The VIN operating range
is 3V to 5.5V. A minimum bypass capacitor of 1µF
should be placed close to the input (VIN) pin and the
ground (GND) pin. Refer to the layout recommendations
section for details on placing the input capacitor (C1).
1000
100
10
EN
The EN pin is equivalent to the enable pin for the linear
drivers on the MIC4802. It can also be used for dimming
applying a PWM signal. See the PWM Dimming
Interface in the Application Information section for
details. Pulling the EN low for more than 40ms puts the
MIC4802 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 than 60µs to wake the part up
in a known state. This equates to an 8.3kHz 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.
1
1
10
100
1000
10000
RSET (kΩ)
Figure 2. Peak LED Current vs. RSET
D1
The D1 pins are the linear driver inputs for the LED.
Connect the anode of the LED to VIN and the cathode to
the D1 pins. All the D1 pins must be connected together.
The D1 voltage at dropout is the minimum voltage
required by the linear driver in order for the LED to be
fully biased.
RSET
The RSET pin is used to set the peak current of the linear
driver by connecting a RSET resistor to ground. The
theoretical average LED current can be estimated by
equation (1):
GND
The ground pin is the ground path for the linear driver.
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.
I
LED (mA) = 4920 * D / RSET (kΩ)
(1)
(2)
R
SET (kΩ) = 4920 * D / ILED (mA)
D is the duty cycle of the LED current during PWM
dimming. When the device is fully ON the duty cycle
equals 100% (D = 1). A plot of ILED versus RSET is shown
in Figure 2.
Due to DC losses across current paths internal and
external to the package, the calculated RSET resistance
equation is modified by a factor K, where K is calculated
to be 0.280kΩ.
R
SET (kΩ) = 4920 * D / ILED (mA) + 0.280 (kΩ)
(3)
(4)
ILED (mA) = 4920 * D / ((RSET (kΩ) – 0.280 (kΩ))
The modified LED current equation is more accurate in
determining the actual LED current based on the RSET
resistor value.
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Micrel Inc.
MIC4802
Application Information
LED Current
vs. PWM Duty Cycle
Ultra Fast PWM™ Dimming Interface
900
800
700
600
500
400
300
200
100
0
The MIC4802 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.
fPWM = 20kHz
fPWM = 100kHz
fPWM = 200kHz
WLED dimming is achieved by applying a pulse width
modulated (PWM) signal to the END pin. For PWM
frequencies between 200Hz – 10kHz the MIC4802
supports a duty cycle range from 1% to 100%, as shown
in Figure 3. The MIC4802 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
MIC4802 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, as shown in Figure 4 and 5. Figures 6
through 9 show the WLED current response when a
fPWM = 500kHz
0
20
40
60
80
100
DUTY CYCLE (%)
Figure 4. Channel Current Response to PWM Control
Signal Frequencies from 50kHz to 500kHz
Minimum Duty Cycle
vs. Frequency
35
PWM signal is applied to the END pin (1)
.
30
25
20
15
10
5
(1)
From the low IQ sleep mode higher PWM frequencies above 15kHz
require a logic high enable signal for 60μs to first enable the MIC4802
prior to PWM dimming.
LED Current
vs. PWM Duty Cycle
0
900
VIN = 5V
100
1000
10000
100000 1000000
800
fPWM = 1kHz
FREQUENCY (Hz)
700
600
Figure 5. Minimum Duty Cycle
for Varying PWM Frequency
fPWM = 5kHz
500
400
300
200
100
0
fPWM = 10kHz
0
20
40
60
80
100
DUTY CYCLE (%)
Figure 3. Average Current per LED Dimming
by Changing PWM Duty Cycle for PWM Frequencies
up to 20kHz
Figure 6. PWM Signal at 1% Duty Cycle (Iavg = 8mA)
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Micrel Inc.
MIC4802
Thermal Consideration
The MIC4802 thermal considerations involve calculating
the junction temperature based on the voltage drop
across the package and the LED current. The voltage
drop across the package is equal to the voltage at D1
with respect to ground times the LED current.
PLOSS = ILED * VD1
The temperature rise (ΔT) is calculated:
ΔT = PLOSS * θJA
Assuming the ILED is 800mA and VD1 is 500mV at 20°C
room temperature, we can calculate the junction
temperature:
TJ = TA + ΔT
TJ = 20°C + 0.4W * 41°C/W
TJ = 20°C + 16.4°C = 36.4°C
The junction temperature will be 36.4°C.
Figure 7. PWM Signal at 20% Duty Cycle (Iavg = 160mA)
Figure 8. PWM Signal at 50% Duty Cycle (Iavg = 400mA)
Figure 9. PWM Signal at 80% Duty Cycle (Iavg = 640mA)
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Micrel Inc.
MIC4802
MIC4802 Typical Application Circuit
Bill of Materials
Item
Part Number
C1608X5R0J225K
06036D225KAT2A
GRM188R60J225KE19D
VJ0603G225KXYAT
Manufacturer
TDK(1)
Description
Qty.
AVX(2)
Murata(3)
Vishay(4)
C1
Ceramic Capacitor, 2.2µF, 6.3V, X5R, Size 0603
1
LED
RSET
R42180
Seoul Semiconductor(5)
Vishay(4)
3.8W High Power WLED
1
1
CRCW06036K19FKEA
Resistor, 6.19kΩ, 1%, 1/16W, Size 0603
800mA Single Channel Ultra Fast PWM™
Linear WLED Driver
U1
MIC4802YME
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. Seoul Semi: http://www.acriche.com/en
6. Micrel, Inc.: www.micrel.com
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Micrel Inc.
MIC4802
Layout Recommendations
Top Layer
Bottom Layer
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Micrel Inc.
MIC4802
Package Information
8-Pin SOIC (ME)
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.
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indemnify Micrel for any damages resulting from such use or sale.
© 2010 Micrel, Incorporated.
M9999-013111-B
January 2011
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