View MIC4801YM_5123531.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

mic4801 high efficiency 600ma single channel linear wled driver with ultra fast pwm? control 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 m9999-011811-a general description the mic4801 is a high efficiency white led (wled) driver designed to drive a single led up to 600ma. the mic4801 constant current driver is designed to drive high power led?s in various lighting applications. the mic4801 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 130mv at 400ma. 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 unifor m 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 mic4801 is available in an 8-pin soic 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 ? high efficiency (no voltage boost losses) ? ultra fast pwm? control (200hz to 500khz) ? input voltage range: 3.0v to 5.5v ? dropout of 130mv at 400ma ? 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
micrel inc. mic4801 january 2011 2 m9999-011811-a ordering information part number temperature range package MIC4801YM ?40c to +125c 8-pin soic pin configuration 8-pin soic (m) (top view) pin description pin number pin name pin function 1 vin voltage input. connect at least 2. 2f ceramic capacitor between vin and gnd. 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 12.1k ? resistor between rset and gnd to set led current to 416ma at 100% duty cycle. 4 gnd ground. 5 d1 led1 driver input. connect led anode to vin and cathode to this pin. all d1 pins must be connected to the led. 6 d1 led1 driver input. connect led anode to vin and cathode to this pin. all d1 pins must be connected to the led. 7 d1 led1 driver input. connect led anode to vin and cathode to this pin. all d1 pins must be connected to the led. 8 d1 led1 driver input. connect led anode to vin and cathode to this pin. all d1 pins must be connected to the led.
micrel inc. mic4801 january 2011 3 m9999-011811-a absolute maximum ratings (1) main input voltage (v in ) .................................. ?0.3v to +6v enable input voltage (v en ).............................. ?0.3v to +6v led driver voltage (v d1 ) ................................ ?0.3v to +6v power dissipation .....................................in ternally limited lead temperature (solde ring, 10sec .)....................... 260c storage temperature (t s ) .........................?65c to +150c operating ratings (2) supply voltage (v in )..................................... +3.0v to +5.5v enable input voltage (v en ) .................................... 0v to v in led driver voltage (v d1 ) ....................................... 0v to v in junction temperature (t j ) ........................ ?40c to +125c junction thermal resistance soic-8l ( ja )..................................................98.9c/w electrical characteristics v in = v en = 5v, r set = 12.1k ? ; v d1 = 1.2v; t j = 25 c, bold values indicate ?40 c t j 125 c; unless noted. parameter conditions min typ max units current accuracy (3) 374 416 458 ma drop-out where i led = 90% of led current seen at v dropnom = 1.2v, 100% brightness level 130 250 mv ground/supply bias current i out = 416ma 2.2 2.9 ma shutdown current v en = 0v 0.01 1 a pwm dimming logic low 0.2 v enable input voltage (v en ) logic high 1.2 v enable input current v ih > 1.2v 0.01 1 a current source delay (50% levels) shutdown to on standby to on on to standby 40 2 0.3 60 s s s current source transient time (10%-90%) t rise t fall 1 0.3 s s stand-by to shutdown time v en = 0v 10 20 40 ms notes: 1. exceeding the absolute maxi mum 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 r set resistance.
micrel inc. mic4801 january 2011 4 m9999-011811-a typical characteristics led current vs. led anode voltage 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 2.5 3 3.5 4 4.5 5 5.5 led anode voltage (v) led current (a) vin = 5.5v vin = 3.5v vin = 3.0v dropout voltage vs. led current 0 25 50 75 100 125 150 175 200 225 250 275 300 0 100 200 300 400 500 600 700 800 led current (ma) dropout voltage (mv ) vin = 5v supply bias current vs. led anode voltage 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 2.5 3 3.5 4 4.5 5 5.5 led anode voltage (v) supply bias current (ma ) vin = 5.5v vin = 2.5v vin = 3.0v r set = 4.64k ? peak led current vs. r set 1 10 100 1000 1 10 100 1000 10000 rset (k ? ) iled (ma) led current vs. pwm duty cycle 0 100 200 300 400 500 600 700 800 900 0 20406080100 duty cycle (%) led current (ma) f pwm = 10khz f pwm = 5khz f pwm = 1khz vin = 5v led current vs. pwm duty cycle 0 100 200 300 400 500 600 700 800 900 0 20406080100 duty cycle (%) led current (ma) f pwm = 20khz f pwm = 200khz f pwm = 100khz f pwm = 500khz rset voltage vs. led current 1.25 1.26 1.27 1.28 1.29 1.3 1.31 1.32 1.33 1.34 0 100 200 300 400 500 600 700 800 led current (ma) rset voltage (v) vin = 5v typical i led vs. v led 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.4 2.6 2.8 3 3.2 3.4 3.6 led forward voltage (v) led current (a) vin = 5.0v
micrel inc. mic4801 january 2011 5 m9999-011811-a functional characteristics
micrel inc. mic4801 january 2011 6 m9999-011811-a functional diagram figure 1. mic4801 functional block diagram functional description the mic4801 is a single channel linear led driver with a maximum 600ma current capability. the led driver is designed to maintain proper current regulation with led current accuracy of 10%. the dropout is 130mv at 400ma. 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 mic4801 accommodates a wide pwm frequency range as outlined in the application information section. block diagram as shown in figure 1, the mi c4801 consists of current mirrors set to copy a master current determined by r set . the linear led drivers have a designated control block for enabling and dimming of the leds. the mic4801 dimming is controlled by the ultra fast pwm? control block that receives pwm signals for dimming.
micrel inc. mic4801 january 2011 7 m9999-011811-a vin the input supply (v in ) provides power to the linear led drivers and the control circuitry. the v in operating range is 3v to 5.5v. a minimum bypass capacitor of 2.2f 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 mic4801. it can also be used for dimming by applying a pwm signal. see the pwm dimming interface in the applicati on information section for details. pulling the en low for more than 40ms puts the mic4801 into a low i q sleep mode. the en pin cannot be left floating; a floating enable pin may cause an indeterminate state on the output s. 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 a 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 r set pin is used to set the peak current of the linear driver by connecting a r set resistor to ground. the theoretical average led cu rrent can be estimated by equation (1): i led (ma) = 4920 * d / r set (k ? ) (1) r set (k ? ) = 4920 * d / i led (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 i led versus r set is shown in figure 2. due to dc losses across current paths internal and external to the package, the calculated r set resistance equation is modified by a factor k, where k is calculated to be 0.140k ? . r set (k ? ) = 4920 * d / i led (ma) + 0.140 (k ? ) (3) i led (ma) = 4920 * d / ((r set (k ? ) ? 0.140 (k ? )) (4) the modified led current equation is more accurate in determining the actual led current based on the rset resistor value. peak led current vs. r set 1 10 100 1000 1 10 100 1000 10000 rset (k ? ) iled (ma) figure 2. peak led current vs. r set 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 capac itor 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.
micrel inc. mic4801 january 2011 8 m9999-011811-a application information ultra fast pwm? dimming interface the mic4801 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 en pin. for pwm frequencies between 200hz ? 10khz the mic4801 supports a duty cycle range from 1% to 100%, as shown in figure 3. the mic4801 incorporates an internal shutdown delay to ensure that the internal control circuitry remains active during pwm dimming. this feature prevents the possibilit y of backlight flickering when using low frequency pwm control signals. the mic4801 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 3 and 4. figures 6 through 9 show the wled current response when a pwm signal is applied to the en pin (1) . (1) from the low i q sleep mode higher pwm frequencies require a logic high enable signal for 60 s to first enable the mic4801 prior to pwm dimming. led current vs. pwm duty cycle 0 100 200 300 400 500 600 700 800 900 0 20406080100 duty cycle (%) led current (ma) f pwm = 10khz f pwm = 5khz f pwm = 1khz vin = 5v figure 3. average current per led dimming by changing pwm duty cycle for pwm frequencies up to 20khz led current vs. pwm duty cycle 0 100 200 300 400 500 600 700 800 900 0 20 40 60 80 100 duty cycle (%) led current (ma) f pwm = 20khz f pwm = 200khz f pwm = 100khz f pwm = 500khz figure 4. channel current response to pwm control signal frequencies from 50khz to 500khz minimum duty cycle vs. frequency 0 5 10 15 20 25 30 35 100 1000 10000 100000 1000000 frequency (hz) minimum duty (%) figure 5. minimum duty cycle for varying pwm frequency figure 6. pwm signal at 1% duty cycle (i avg = 6ma)
micrel inc. mic4801 january 2011 9 m9999-011811-a figure 7. pwm signal at 20% duty cycle (i avg = 120ma) figure 8. pwm signal at 50% duty cycle (i avg = 300ma) figure 9. pwm signal at 80% duty cycle (i avg = 480ma) thermal consideration the mic4801 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. p loss = i led * v d1 the temperature rise ( t) is calculated: t = p loss * ja assuming the i led is 600ma and v d1 is 500mv at 20c room temperature, we can calculate the junction temperature: t j = t a + t t j = 20c + 0.3w * 98.9c/w t j = 20c + 29.7c = 49.7c the junction temperature will be around 49.7c.
micrel inc. mic4801 january 2011 10 m9999-011811-a mic4801 typical a pplication circuit bill of materials item part number manufacturer description qty. c1608x5r0j225k tdk (1) 06036d225kat2a avx (2) grm188r60j225ke19d murata (3) c1 vj0603g225kxyat vishay (4) ceramic capacitor, 2.2f, 6.3v, x5r, size 0603 1 led r42180 seoul semiconductor (5) 3.8w high power wled 1 r1 crcw060312k1fkea vishay (4) resistor, 1%, 1/16w, size 0603 1 u1 MIC4801YM micrel, inc. (6) 600ma single channel ultra fast pwm? linear wled driver 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
micrel inc. mic4801 january 2011 11 m9999-011811-a layout recommendations top layer bottom layer
micrel inc. mic4801 january 2011 12 m9999-011811-a package information 8-pin soic (m) 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 t he 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 it s use. micrel reserves the right to change circuitry, specifications and descriptions at any time without notice. no license, whether expre ss, implied, arising by estoppel or other wise, to any intellectual property rights is granted by this document. except as provided in micrel?s terms and conditions of sale for such products, mi crel assumes no liability whatsoever, and micrel disclaims any express or implied warranty relating to the sale and/or use of micrel products including l iability or warranties relating to fitness for a particular purpose, merchantability, or infringement of an y patent, copyright or other intellectual p roperty right. micrel products are not designed or authori zed for use as components in life support app liances, devices or systems where malfu nction of a product can reasonably be expected to result in pers onal injury. life support devices or system s are devices or systems that (a) are int ended 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 significan t injury to the user. a purchaser?s use or sale of micrel produc ts for use in life support app liances, 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.

▲Up To Search▲

Price & Availability of MIC4801YM

	To Download MIC4801YM Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .