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mic2860-p high efficiency 2 channel wled driver with pwm control mlf and micro leadframe are registered trademark amkor technology 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 general description the mic2860-2p 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 mob ile devices. the mic2860-2p architecture provides the hi ghest 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 typical matching of 0.5%, which ensures uniform display illumination under all conditions. the wleds brightness is exter nally preset by a resistor and dimmed using pwm interface operating down to less than 1% duty cycle. the mic2860-2p 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 micrels web site at: www.micrel.com . features ? high efficiency (no switching losses) ? pwm frequency as low as 250hz ? input voltage range: 3.0v to 5.5v ? linear 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 packages applications ? mobile handsets ? digital cameras ? portable media/mp3 players ? portable navigation devices (gps) ? portable applications ____________________________________________________________________________________________________________ typical application lcd display backlight with 2 wleds september 2010 m9999-092710-a downloaded from: http:///
micrel inc. mic2860-2p september 2010 2 m9999-092710-a ordering information part number mark code (1) junction temperature range package (2) mic2860-2pyc6 62 p C40c to +125c 6-pin sc-70 mic2860-2pyd6 602 p C40c to +125c 6-pin thin sot-23 notes: 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 mic2860-2p pin name pin function 1 en pwm control pin. this pin is used as a pwm input for dimming of wleds. 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. 5 rset an internal 1.27v reference sets the nominal maximum wled current. example, apply a 9.53k ? resistor between rset and gnd to set led current to 30.2ma at 100% duty cycle. 6 d1 led1 driver. connect led anode to vin and ca thode to this pin. do not leave floating. downloaded from: http:///
micrel inc. mic2860-2p september 2010 3 m9999-092710-a absolute maximum ratings (1) main input voltage (v in ) .................................. C0.3v to +6v enable input voltage (v en )................................ C0.3v to v in led driver voltage (v d1, d2 ) ............................. C0.3v to v in power dissipation .....................................in ternally limited lead temperature (solder ing, 10sec .)....................... 260c storage temperature (t s ) .........................C65c to +150c esd rati ng.................................................................... 2kv 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, d2 ) .................................. 0v to v in junction temperature (t j ) ........................ C40c to +125c junction thermal resistance sc-70 ( ja ).....................................................256 c /w sot-23 ( ja ) ..................................................177 c /w electrical characteristics wled linear drivers v in = v en = 3.6v, c in = 1f, r set = 9.53k ? ; v d1, d2 = 0.6v; t j = 25 c, bold values indicate C40 c t j 85 c; unless noted. parameter conditions min. typ. max. units current accuracy (3) 27.18 30.2 33.22 ma matching (4) 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 en = 0v 0.01 1 a pwm dimming logic low 0.4 v enable input voltage (v en ) logic high 1.4 v enable input current v en 1.4 0.01 1 a current-source delay (50% levels) shutdown to on standby to on on to standby 32 1.5 0.3 80 4 s current-source transient time (10% ? 90%) t rise t fall 0.7 0.2 s on-to-shutdown time v en = 0v 4 5.8 10 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 of all channels in use and all channels loaded. 4. the current through each led meets the stated limits from the average current of all leds. downloaded from: http:///
micrel inc. mic2860-2p september 2010 4 m9999-092710-a typical characteristics peak led current vs. r set 0 5 10 15 20 25 30 35 5 101520253035 r set (k ? ) led current (ma) dropout voltage vs. r set 0 10 20 30 40 50 60 70 0 1 02 03 04 r set (k ? ) current sink dropout (mv) led1 led2 0 dropout voltage vs. temperature 0 10 20 30 40 50 60 70 -40-20 0 20406080100120 temperature (c) led dropout (mv) led1 led2 r set = 9.53k ? dropout voltage vs. temperature 0 5 10 15 20 25 30 35 -40-20 0 20406080100120 temperature (c) led dropout (mv) r set = 19.1k ? led1 led2 led current vs. temperature 28 28.5 29 29.5 30 30.5 31 31.5 32 -40 -20 0 20 40 60 80 100 120 temperature (c) led current (ma) led1 led2 r set = 9.53k ? led current vs.temperature 13 13.5 14 14.5 15 15.5 16 -40-20020406080100120 temperature (c) led current (ma) r set = 19.1k ? iled1 iled2 matching vs. temperature 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 -40-20 0 20406080100120 temperature (c) matching (%) r set = 9.53k ? r set = 19.1k ? downloaded from: http:///
micrel inc. mic2860-2p september 2010 5 m9999-092710-a functional characteristics downloaded from: http:///
micrel inc. mic2860-2p september 2010 6 m9999-092710-a functional characteristics (continued) downloaded from: http:///
micrel inc. mic2860-2p september 2010 7 m9999-092710-a functional diagram figure 1. mic2860-2p functional block diagram downloaded from: http:///
micrel inc. mic2860-2p september 2010 8 m9999-092710-a functional description the mic2860-2p is a two channel wled driver. the wled driver is designed to maintain proper current regulation with led current accuracy of 1% with a typical matching between the 2 channels of 0.5%. 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 peak wled current for each channel is set via an external resistor. if dimming is desired the mic2860-2p can dim via a pwm signal. block diagram as shown in figure 1, the mic2860-2p consists of two current sinks with the peak current determined by r set . the linear drivers have a designated control block for enabling and dimming of the wleds. the mic2860-2p is controlled by the pwm c ontrol block that receives pwm signals for dimming. vin 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 input (vin) pin and the ground (gnd) pin. en the en pin enables the linear drivers. it can also be used for dimming with a pwm signal. see the pwm dimming interface in the application information section for details. do not leave floating. r set the r set pin is used by connecting a r set resistor to ground to set the peak current of the linear drivers. the maximum led current (en = 100% duty cycle) set by the r set resistor is shown in the table below: 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 table 1. maximum led current vs. r set resistor values a plot of 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) figure 2. peak led current vs. r set 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. downloaded from: http:///
micrel inc. mic2860-2p september 2010 9 m9999-092710-a application information pwm dimming interface the mic2860-2p can receive pwm signals from the en pin for wled dimming. dimming is generated by pulsing the wleds on and off in synchronization with the pwm signal. the mic2860-2p incorporates an internal shutdown delay to ensure that the internal control circuitry remains active during pwm dimming for optimum performance. the lower pwm frequency range is recommended at 250hz due to the minimum standby to shutdown time of 4ms. as the period of 250hz is 4ms, a 1% duty cycle would have an on time of 40us and an off time of 3.96ms. to support operation down to 1% duty cycle, the maximum off time must not exceed 4ms or the drivers may go into the low iq shutdown state. with pwm frequencies higher than 500hz the t rise (0.7 s) and t fall (0.2 s) times will have a greater effect on the accuracy of the output s. an upper frequency of 500hz is recommended to maintain output accuracy with duty cycles down to 1%. for systems that do not require a duty cycle below 1%, the frequency of the pwm signal may be increased. for example, with a minimum duty cycle of 10% (3.02ma with r set = 9.53k ? ) the pwm frequency can be increased to 10khz and still maintain accuracy. input capacitor the mic2860-2p 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 with 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. downloaded from: http:///
micrel inc. mic2860-2p september 2010 10 m9999-092710-a mic2860-2p 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 mic2860-2pyc6 mic2860-2pyd6 micrel, inc. (3) 2-channel pwm linear wled driver, sc-70 2-channel pwm linear wled driver, sot-23 1 notes: 1. tdk: www.tdk.com . 2. vishay: www.vishay.com . 3. micrel, inc.: www.micrel.com . downloaded from: http:///
micrel inc. mic2860-2p september 2010 11 m9999-092710-a package information 6-pin sc-70 (c6) downloaded from: http:///
micrel inc. mic2860-2p september 2010 12 m9999-092710-a package information (continued) 6-pin thin sot-23 (d6) 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 its 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 micrels 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 any 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 in tended 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 si gnificant injury to the user. a purchasers use or sale of micrel produc ts for use in life support app liances, devices or systems is a purchasers own risk and purchaser agrees to fully indemnify micrel for any damages resulting from such use or sale. ? 2010 micrel, incorporated. downloaded from: http:///

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