View MIC4802YME_27923.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

MIC4802
High Efficiency 800mA Single Channel Linear WLED Driver with Ultra Fast PWMTM Control
General Description
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 PWMTM Control interface operating down to less than 1% duty cycle. The MIC4802 is available in the 8-pin SOIC Epad package with a junction temperature range of -40C to +125C. Datasheets and support documentation can be found on Micrel's web site at: www.micrel.com.
Features
* * * * * * High Efficiency (no Voltage Boost losses) Ultra Fast PWMTM 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
____________________________________________________________________________________________________________
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
January 2011
M9999-013111-B
Micrel Inc.
MIC4802
Ordering Information
Part Number MIC4802YME Temperature Range -40C to +125C Package 8-Pin EPAD SOIC
Pin Configuration
8-Pin Epad SOIC (ME) (Top View)
Pin Description
Pin Number 1 2 3 4 5 6 7 8 EPAD Pin Name VIN EN RSET GND D1 D1 D1 D1 HS PAD Pin Function Voltage Input. Connect at least 2.2F ceramic capacitor between VIN and GND. Enable LED drivers. This pin can be used as a PWM input for dimming of WLEDs. Do not leave floating. An internal 1.27V reference sets the nominal maximum WLED current. Example, apply a 6.19k resistor between RSET and GND to set LED current to 830mA at 100% duty cycle. Ground. LED1 driver input. Connect LED anode to VIN and cathode to this pin. All D1 pins must be connected to the LED. LED1 driver input. Connect LED anode to VIN and cathode to this pin. All D1 pins must be connected to the LED. LED1 driver input. Connect LED anode to VIN and cathode to this pin. All D1 pins must be connected to the LED. LED1 driver input. Connect LED anode to VIN and cathode to this pin. All D1 pins must be connected to the LED. Heat sink pad. Not internally connected. Connect to ground.
January 2011
2
M9999-013111-B
Micrel Inc.
MIC4802
Absolute Maximum Ratings(1)
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.)....................... 260C Storage Temperature (Ts) .........................-65C to +150C
Operating Ratings(2)
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) ........................ -40C to +125C Junction Thermal Resistance EPAD SOIC-8L (JA)..........................................41C/W
Electrical Characteristics
VIN = VEN = 5V, RSET = 6.19k; VD1 = 1.2V; TJ = 25C, bold values indicate -40C TJ 125C; unless noted.
Parameter Current Accuracy Drop-out Ground/Supply Bias Current Shutdown Current PWM Dimming Enable Input Voltage (VEN) Enable Input Current Current Source Delay (50% levels) Current Source Transient Time (10%-90%) Stand-by to Shutdown 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. As determined by average current based on RSET resistance.
(3)
Conditions Where ILED = 90% of LED current seen at VDROPNOM = 1.2V, 100% brightness level IOUT = 830mA VEN = 0V Logic Low Logic High VIH > 1.2V Shutdown to on Standby to on On to Standby TRISE TFALL VEN = 0V
Min 747
Typ 830 280 4.1 0.01
Max 913 500 5.7 1 0.2
Units mA mV mA A V V A s s s s s
1.2 0.01 40 2 0.3 1 0.3 10 20 40 1 60
ms
January 2011
3
M9999-013111-B
Micrel Inc.
MIC4802
Typical Characteristics
1.4 1.2
LED Battery Voltage vs. LED Current
VIN = 5.5V
LED CURRENT (A)
1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
LED Current vs. LED Anode Voltage
VIN = 5.5V
Dropout Voltage vs. LED Current
500 450 DROPOUT VOLTAGE (mV) 400 350 300 250 200 150 100 50 VIN = 5V 0 200 400 600 800 1000 1200 1400 0 LED CURRENT (mA)
LED CURRENT (A)
1 0.8 0.6 0.4 0.2 0 5.5 5 4.5 4 3.5
VIN = 3.5V VIN = 3.0V
VIN = 3.5V VIN = 3.0V
3
2.5
5.5
5
4.5
4
3.5
3
2.5
LED BATTERY VOLTAGE (V)
LED ANODE VOLTAGE (V)
Supply Bias Current vs. LED Anode Voltage
8 Supply Bias Current (mA) 7 6
ILED (mA) 10000
Peak LED Current vs. RSET
LED Current vs. PWM Duty Cycle
900 800
VIN = 5V
VIN = 5.5V
1000
fPWM = 1kHz
LED CURRENT (mA)
700 600 500 400 300 200 100 fPWM = 10kHz fPWM = 5kHz
5 4 3 2 1 0 5.5 5 4.5 4 3.5 3 2.5 LED BATTERY VOLTAGE (V) RSET = 4.64k VIN = 2.5V VIN = 3.5V
100
10
1 1 10 100 RSET (k) 1000 10000
0 0 20 40 60 80 100 DUTY CYCLE (%)
LED Current vs. PWM Duty Cycle
900 800 LED CURRENT (mA) 700 600 500 400 300 200 100 0 0 20 40 60 80 100 DUTY CYCLE (%) fPWM = 500kHz fPWM = 200kHz fPWM = 100kHz fPWM = 20kHz
RSET Voltage vs. LED Current
1.4 1.38 RSET VOLTAGE (V)
LED CURRENT (A) 2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4
Typical ILED vs. VLED
VIN = 5.0V
1.36 1.34 1.32 1.3 1.28 1.26 1.24 0 200 400 600 800 1000 1200 1400 LED CURRENT (mA) VIN = 5V
0.2 0 2.4 2.6 2.8 3 3.2 3.4 3.6 LED FORWARD VOLTAGE (V)
January 2011
4
M9999-013111-B
Micrel Inc.
MIC4802
Functional Characteristics
January 2011
5
M9999-013111-B
Micrel Inc.
MIC4802
Functional Diagram
Figure 1. MIC4802 Functional Block Diagram
Functional Description
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.
Block Diagram 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.
January 2011
6
M9999-013111-B
Micrel Inc. VIN 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 1F 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). 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 60s 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 60s. 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): ILED (mA) = 4920 * D / RSET (k) (1) RSET (k) = 4920 * D / ILED (mA) (2) 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 0.280k. RSET (k) = 4920 * D / ILED (mA) + 0.280 (k) ILED (mA) = 4920 * D / ((RSET (k) - 0.280 (k)) (3) (4)
MIC4802
1000
Peak LED Current vs. RSET
ILED (mA)
100
10
1 1 10 100 RSET (k) 1000 10000
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. 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.
The modified LED current equation is more accurate in determining the actual LED current based on the RSET resistor value.
January 2011
7
M9999-013111-B
Micrel Inc.
MIC4802
LED Current vs. PWM Duty Cycle
900 800 LED CURRENT (mA) 700 600 500 400 300 200 100 0 0 20 40 60 80 100 DUTY CYCLE (%) fPWM = 500kHz fPWM = 200kHz fPWM = 100kHz fPWM = 20kHz
Application Information
Ultra Fast PWMTM Dimming Interface 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. 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 PWMTM 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 PWM signal is applied to the END pin (1).
From the low IQ sleep mode higher PWM frequencies above 15kHz require a logic high enable signal for 60s to first enable the MIC4802 prior to PWM dimming.
(1)
Figure 4. Channel Current Response to PWM Control Signal Frequencies from 50kHz to 500kHz
Minimum Duty Cycle vs. Frequency
35 30 MINIMUM DUTY (%) 25 20 15 10 5 0 100
LED Current vs. PWM Duty Cycle
900 800 LED CURRENT (mA) 700 600 500 400 300 200 100 0 0 20 40 60 80 100 DUTY CYCLE (%) fPWM = 10kHz fPWM = 5kHz
VIN = 5V
fPWM = 1kHz
1000
10000
100000
1000000
FREQUENCY (Hz)
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
Figure 6. PWM Signal at 1% Duty Cycle (Iavg = 8mA)
January 2011
8
M9999-013111-B
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 (T) is calculated: T = PLOSS * JA Assuming the ILED is 800mA and VD1 is 500mV at 20C room temperature, we can calculate the junction temperature: TJ = TA + T TJ = 20C + 0.4W * 41C/W TJ = 20C + 16.4C = 36.4C The junction temperature will be 36.4C.
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)
January 2011
9
M9999-013111-B
Micrel Inc.
MIC4802
MIC4802 Typical Application Circuit
Bill of Materials
Item Part Number C1608X5R0J225K C1 06036D225KAT2A GRM188R60J225KE19D VJ0603G225KXYAT LED RSET U1
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
Manufacturer TDK(1) AVX(2) Murata(3) Vishay(4) Seoul Semiconductor(5) Vishay
(4)
Description
Qty.
Ceramic Capacitor, 2.2F, 6.3V, X5R, Size 0603
1
R42180 CRCW06036K19FKEA MIC4802YME
3.8W High Power WLED Resistor, 6.19k, 1%, 1/16W, Size 0603 800mA Single Channel Ultra Fast PWMTM Linear WLED Driver
1 1 1
Micrel, Inc.(6)
January 2011
10
M9999-013111-B
Micrel Inc.
MIC4802
Layout Recommendations
Top Layer
Bottom Layer
January 2011
11
M9999-013111-B
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. 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. (c) 2010 Micrel, Incorporated.
January 2011
12
M9999-013111-B

▲Up To Search▲

Price & Availability of MIC4802YME

	To Download MIC4802YME Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .