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mic2860-d high efficiency 2 channel wled driver with single wire digital control micrel inc. ? 2180 fortune drive ? san jose, ca 95131 ? usa ? tel +1 ( 408 ) 944-0800 ? fax + 1 (408) 474-1000 ? http://www.micrel.com general description the mic2860-2d is a high efficiency white led (wled) driver designed to drive two wleds and greatly extend battery life for portable display backlighting, and keypad backlighting in low cost mobile devices. the mic2860-2d architecture provides the highest possible efficiency by eliminating switching losses present in traditional charge pumps or inductive boost circuits. it features a typical dropout of 52mv at 30.2ma per channel. this allows the wleds to be driven directly from the battery eliminating switching noise and losses present with the use of boost circuitry. the two channels have better than 0.5% matching, which ensures uniform display illumination under all conditions. the wleds brightness is exter nally preset by a resistor and dimmed using a single wire digital control signal. the mic2860-2d single wire digital interface accepts digital programming pulses providing 32 dimming steps. the mic2860-2d is available in thin sot-23 and sc-70 six pin packages 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 switching losses) ? no charge pumps ? 2 wled driver channels ? single wire digital control ? input voltage range: 3.0v to 5.5v ? wled driver dropout of 52mv at 30.2ma ? matching better than 0.5% (typical) ? current accuracy better than 1.0% (typical) ? available in thin sot-23 and sc-70 6 pin packages applications ? mobile handsets ? digital cameras ? portable media/mp3 players ? portable navigation devices (gps) ? portable applications ____________________________________________________________________________________________________________ typical application lcd display backlight with 2 wleds july 2010 m9999-072010-a
micrel inc. mic2860-2d july 2010 2 m9999-072010-a ordering information part number mark code (1) temperature range package (2) MIC2860-2DYC6 62 d ?40c to +85c 6-pin sc-70 mic2860-2dyd6 602 d ?40c to +85c 6-pin thin sot-23 note: 1. under bar symbol ( _ ) may not be to scale. 2. package is green rohs compliant. lead fini sh is nipdau. mold compound is halogen free. pin configuration 6-pin sc-70 (c6) (top view) 6-pin thin sot-23 (d6) (top view) pin description pin number mic2860-2d pin name pin function 1 sc serial control digital input. do not leave floating. 2 gnd ground. 3 vin voltage input. connect at least 1f ce ramic capacitor between vin and gnd. 4 d2 led2 driver. connect led anode to vin and ca thode to this pin. do not leave floating. (1) 5 rset connect an external resistor from this pin to gnd to set the maximu m led current. example, apply a 9.53k ? resistor between rset and gnd to set led current to 30ma at 100% duty cycle. 6 d1 led1 driver. connect led anode to vin and ca thode to this pin. do not leave floating. (1) note 1. when driving only 1 led, connect d1 and d2 in parallel to t he led cathode and adjust the rset resistor for half the desired ou tput.
micrel inc. mic2860-2d july 2010 3 m9999-072010-a absolute maximum ratings (1) main input voltage (v in ) ................................... -0.3v to +6v enable input voltage (v sc ).................................-0.3v to v in led driver voltage (v d1, d2 ) ..............................-0.3v to v in power dissipation .....................................in ternally limited lead temperature (solde ring, 10sec .) ....................... 260c storage temperature (t s ) ..........................-65c to +150c esd rating (3) ................................................. esd sensitive operating ratings (2) supply voltage (v in )..................................... +3.0v to +5.5v enable input voltage (v sc ) .................................... 0v to v in led driver voltage (v d1, d2 ) .................................. 0v to v in junction temperature (t j ) ........................ ?40c to +125c junction thermal resistance sc-70 ( ja ).....................................................256 c /w sot-23 ( ja ) ..................................................177 c /w electrical characteristics v in = v sc = 3.6v, c in = 1f, r set = 9.53k ? ; v d1, d2 = 0.6v; t j = 25 c, bold values indicate ?40 c ? t j ? 85 c; unless noted. parameter conditions min typ max units current accuracy (4) 27.18 30.2 33.22 ma matching (5) 0.5 3 % drop-out (v d1, d2 ) where i led = 90% of led current seen at v dropnom = 0.6v, 100% brightness level 52 125 mv ground/supply bias current i out = 30.2ma 0.7 1.5 ma shutdown current (current source leakage) v sc = 0v > 500s 0.01 1 a digital dimming logic low 0.4 v v sc input voltage logic high 1.4 v v sc enable input current v sc = 1.2v 0.01 1 a t shutdown time sc pin is low to put into shutdown 100 500 s t prog_high , t prog_low time for valid sc edge; ignored if outside limit range 0.3 75 s t start_up delay from sc is high to start up 33 s 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, 1.5k ? 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.
micrel inc. mic2860-2d july 2010 4 m9999-072010-a typical characteristics dropout voltage vs. r set 0 10 20 30 40 50 60 70 5 101520253035 r set (k ? ) dropout voltage (mv ) led1 led2 peak led current vs. r set 0 5 10 15 20 25 30 35 8 121620242832 r set (k ? ) led current (ma) dropout voltage vs. brightness level 0 25 50 75 100 125 0 5 10 15 20 25 30 35 brightness level dropout voltage (mv ) led2 led1 r set = 9.53k dropout voltage vs. temperature 0 20 40 60 80 100 -40 -20 0 20 40 60 80 100 120 temperature (c) dropout voltage (mv ) bl-31 bl-0 bl-11 bl-21 r set = 9.53k matching vs. temperature 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 -40 -20 0 20 40 60 80 100 120 temperature (c) matching (%) bl-31 bl-21 bl-11 r set = 9.53k led current vs.temperature 28.0 28.5 29.0 29.5 30.0 30.5 31.0 31.5 32.0 -40 -20 0 20 40 60 80 100 temperature (c) led current (ma) led1-bl31 led2-bl31 r set = 9.53k led current vs. temperature 18.0 18.5 19.0 19.5 20.0 20.5 21.0 21.5 22.0 -40 -20 0 20 40 60 80 100 120 temperature (c) led current (ma) led1-bl21 led2-bl21 r set = 9.53k led current vs. temperature 10.0 10.1 10.2 10.3 10.4 10.5 10.6 10.7 10.8 10.9 11.0 -40 -20 0 20 40 60 80 100 120 temperature (c) led current (ma) led1-bl11 led2-bl11 r set = 9.53k note: bl = brightness level
micrel inc. mic2860-2d july 2010 5 m9999-072010-a functional characteristics
micrel inc. mic2860-2d july 2010 6 m9999-072010-a functional diagram figure 1. mic2860-2d functional block diagram functional description r set the r set pin is used by connecting an r set resistor to ground to set the peak current of the linear drivers. the maximum led current set by the r set resistor is shown in the table below: the mic2860-2d is a 2 channel wled driver. the wled driver is designed to maintain proper current regulation with led current accuracy of 1.0% while the typical matching between the 2 channels is 0.5% at room temperature. the wleds are driven independently from the input supply and will maintain regulation with a dropout of 52mv at 30.2ma. the low dropout of the linear drivers 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 via an external resistor. r set (k ? ) i led (ma) 9.53 30.2 11.5 25.0 14.3 20.1 15.8 18.2 19.1 15.1 28.7 10.0 block diagram as shown in figure 1, the mic2860-2d consists of 2 current mirrors set to copy a master current determined by r set . the linear drivers have a designated control block for enabling and dimming of the wleds. the mic2860-2d dimming is controlled by an internal digital control interface. table 1. maximum led current vs. r set resistor values a plot of maximum i led versus r set is shown in figure 2. peak led current vs. r set 0 5 10 15 20 25 30 35 8 121620242832 r set (k ? ) led current (ma) v in the input supply (v in ) provides power to the linear drivers and the control circuitry. the v in operating range is 3v to 5.5v. due to wire inductance a minimum bypass capacitor of 1f should be placed close to the input (v in ) pin and the ground (gnd) pin. refer to the layout recommendations section for details on placing the input capacitor (c1). sc the sc pin is equivalent to the enable pin for the linear drivers on the mic2860-2d. it can also be used for dimming using a single wire digital interface. see the mic2860-2d digital dimming interface in the application information section for details. do not leave control pins floating. figure 2. peak led current vs. r set
micrel inc. mic2860-2d july 2010 7 m9999-072010-a d1, d2 the d1 and d2 pins are the linear driver inputs for wled 1 and 2 respectively. connect the anodes of the wleds to v in and each cathode of the wleds to d1 and d2. when operating with a single wled, d1 and d2 should be connected to the wled cathode to parallel the outputs for improved dropout performance. paralleling these pins can also be done to drive a higher current through a single wled. do not leave these pins floating 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.
micrel inc. mic2860-2d july 2010 8 m9999-072010-a application information digital dimming interface brightness level (0 - 31) i led (ma) r set =14.3k ? i led (ma) r set =19.1k ? % of max. current 31 20.1 15.1 100 30 19.4 14.6 96.7 29 18.8 14.1 93.7 28 18.2 13.6 90.4 27 17.5 13.1 87.1 26 16.8 12.6 83.8 25 16.2 12.2 80.8 24 15.6 11.7 77.5 23 14.9 11.2 74.2 22 14.2 10.7 70.9 21 13.6 10.2 67.9 20 13.0 9.7 64.6 19 12.3 9.2 61.3 18 11.6 8.7 57.9 17 11.0 8.3 55.0 16 10.4 7.8 51.7 15 9.7 7.3 48.3 14 9.1 6.8 45.0 13 8.5 6.4 42.1 12 7.8 5.8 38.7 11 7.1 5.3 35.4 10 6.5 4.8 32.1 9 5.9 4.4 29.1 8 5.2 3.9 25.8 7 4.5 3.4 22.5 6 3.9 2.9 19.2 5 3.3 2.4 16.2 4 2.6 1.9 12.9 3 1.9 1.4 9.6 2 1.3 0.9 6.3 1 0.7 0.5 3.3 0 0.3 0.2 1.7 table 2. digital interface brightness level table the mic2860-2d incorporates an easy to use single wire, serial programming interface that allows users to set wled brightness up to 32 different levels as shown in table 2. to calculate the brightness level for other r set values, multiply the percentage of max current values by the maximum led current set by the r set resistor value from table 1. for example with r set = 19.1k , the max current (brightness level = 31) is 15.1ma and brightness level 20 would equate to 15.1ma x 0.646 = 9.7ma. brightness levels are linearly spaced with a maximum current equal to 100% of the current set by r set . the mic2860-2d is designed to receive programming pulses to decrease brightness from the initial start up default (level 1 maximum current). once the brightness change signal is received, the sc pin is simply pulled high to maintain the brightness. this ?set and forget? feature relieves processor computing power by eliminating the need to constantly send a pwm signal to the dimming pin. start up assuming the mic2860-2d has been off for a long time, the mic2860-2d will start-up in its default mode approximately 33s (t start_up ) after a logic level high is applied to the sc pin. in the default mode the wleds are turned on at the maxi mum brightness (level 31). each falling edge will cause the default brightness level to decrease by one. figure 3. typical start-up timing shutdown when the sc input pin is pulled low for a period greater than or equal to t shutdown (500s), the mic2860-2d will turn off the current sinks as shown in figure 4. figure 4. shutdown timing once the device is shutdown, the control circuit supply is disabled and the wleds are turned off drawing only 0.01a. brightness level information stored in the mic2860-2d prior to shutdown will be erased and upon a following startup signal the wleds will be turned on at maximum brightness (level 31). programming the brightness level mic2860-2d is designed to start driving the wleds
micrel inc. mic2860-2d july 2010 9 m9999-072010-a 33s (t start_up ) after the sc pin is first pulled high at the maximum brightness level 1. after start up, the internal control logic is ready to decrease the wled brightness upon receiving programming pulses (positive edges applied to sc pin). the brightness level can be decreased one level by applying a single programming pulse as shown in figure 5. brightness settings can be quickly changed by sending programming pulses one after each other. each programming pulse has a high (t prog_high ) and a low (t prog_low ) pulse width that must be between 0.3s to 75s. counter roll-over the mic2860-2d internal counter contains registers from 0 to 31 (32 levels). when the brightness level is at 32 (minimum brightness) and a programming pulse forces the brightness to st ep down, the counter will roll- over to level 31 (maximum bri ghtness). this is illustrated in figure 7. figure 7. down counter roll-over input capacitor the mic2860-2d is a high performance, high bandwidth device. stability can be maintained using a ceramic input capacitor of 1f. low esr ceramic capacitors provide optimal performance at a minimum amount of space. additional high-frequency capacitors, such as small valued npo dielectric type capacitors, help filter out high frequency noise and are good practice in any noise sensitive circuit. 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 5. brightness programming pulses multiple brightness levels can be changed as shown in figure 6. when issuing multiple brightness level adjustments to the sc pin, ensure both t prog_low and t prog_high are within 0.3s and 75s. to maintain operation at the current brightness level simply maintain a logic level high at the sc pin. figure 6. consecutive brightness level commands the mic2860-2d can be programmed to set wled drive current to produce one of 32 distinct brightness levels. the following section explains how the brightness counter functions with continued programming edges.
micrel inc. mic2860-2d july 2010 10 m9999-072010-a mic2860-2d typical application circuit bill of materials item part number manufacturer description qty. c1 c1608x5r0j105k tdk (1) 1f ceramic capacitor, 6.3v, x5r, size 0603 1 r1 crcw06032052ft1 vishay (2) 9.53k ? , 1%, size 0603 1 u1 MIC2860-2DYC6 micrel, inc. (3) 2 channel digital control linear wled driver 1 notes: 1. tdk: www.tdk.com 2. vishay: www.vishay.com 3. micrel, inc.: www.micrel.com
micrel inc. mic2860-2d july 2010 11 m9999-072010-a package information 6-pin sc-70 (c6) 6-pin thin sot-23 (d6)
micrel inc. mic2860-2d july 2010 12 m9999-072010-a 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 the information furnished by micrel in this data sheet is belie ved to be accurate and reliable. however, no responsibility is a ssumed by micrel for its use. micrel reserves the right to change circuitry and specifications at any time without notification to the customer. 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 reasonably be expected to result in pers onal injury. life support devices or system s are devices or systems that (a) are in tended for surgical impla 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 products for use in life support appli ances, devices or systems is at purchaser?s own risk an d purchaser agrees to fully indemnify micrel for any damages resulting from such use or sale. can nt ? 2010 micrel , incor p orated.

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