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| jun29-07 revd SP7120/22 low dropout led driver ? 2007 sipex corporation page 1 features ? led driver for common cathode parallel connected leds ? ultra low dropout voltage of 150mv ? no emi, no switching noise ? integrated current matching ? pwm and analog brightness control ? enable/shutdown control ? shutdown current < 1 a ? lead free, rohs compliant package: small footprint sot23-6 applications ? mobile phones ? pda, dsc, mp3 players ? handheld computers ? keypads and display backlight general description the sp712x driver?s family provides a simple soluti on for a matched current source for any color common cathode led configuration. the common cathode connection allows the user to increase the led power dissipation by having the ca thodes heat-sinked to the ground plane of the circuit board. the SP7120 may drive two leds or one led at twice the current with two channels connected in parallel. the sp7122 can dri ve three leds or one led at three times the current. the factory preset current values are 15ma (version a), 20ma (version b), or 25ma (version c) per channel. in shutdown mode (en pin i s low), the supply current drops to 40na typical. the sp712x drivers are available in a small footpri nt 6-pin sot23-6 package. application schematic SP7120 powering 2 leds 2 or 3 channel low dropout high side linear led driver SP7120/22 c1 1nf
jun29-07 revd SP7120/22 low dropout led driver ? 2007 sipex corporation page 2 absolute maximum ratings these are stress ratings only and functional operat ion of the device at these ratings or any other above those indicated in the operation sections of the specifications below is not implied. exposure to absolute maximum rating conditions for extended period may affect reliability. ambient operating temperature ..?. -40 to+85c vcc, v led1 , v led2 , and en to gnd -0.3v to 6v junction temperature............................+15 0c operating temperature? ..........?.-40 to +85 o c storage temperature...............-65c to +150c package thermal resistance ja ?.?190c/w esd level.......................................... .2kv hbm esd level.......................................... .200v mm esd level en?????? .???.1.5kv hbm lead temperature (soldering, 10 sec) ?300c electrical characteristics specifications are at t a =25?c, vcc = 2.7 to 5.5, enable =vcc parameter min typ max units conditions vcc 2.7 5.5 v shutdown current 0.04 1 a en = low vled dropout voltage, vd 1 160 200 mv vcc = 5.5v, i led = 20ma vled dropout voltage, vd 1 140 180 mv vcc = 5.5v, i led = 15ma version a 15 v d = 300mv version b 20 v d = 300mv led current per channel version c 25 ma v d = 300mv version a 0.5 0.7 version b 0.7 1.1 version c 0.86 1.7 SP7120 at v d = 300mv version a 0.6 0.8 version b 0.9 1.2 quiescent current version c 0.99 1.9 ma sp7122 at v d = 300mv led to led current matching 6 0.8 % vcc = 5.5v, v d > 300mv led current accuracy 2 -3 3 % 300mv jun29-07 revd SP7120/22 low dropout led driver ? 2007 sipex corporation page 4 output current selection table part number output current per channel number of channels comments SP7120a 15ma 2 channels can be combined for higher output current SP7120b 20ma 2 channels can be combined for higher output current SP7120c 25ma 2 channels can be combined for higher output current sp7122a 15ma 3 channels can be combined for higher output current sp7122b 20ma 3 channels can be combined for higher output current sp7122c 25ma 3 channels can be combined for higher output current circuit description the sp712x drivers are regulated current sources with an enable input. the SP7120 and sp7122 have factory preset led current at three programmed levels: 15ma, 20ma or 25ma (versions a, b, and c respectively). the sp712x circuit consists of enable, bandgap reference, and current amplifier circuit blocks. enable circuit block provides the enable and pwm function for the sp712x. the bandgap reference provides a stable voltage source from which the output current is derived. enable the sp712x drivers have a low current shutdown function. in shutdown mode, the part draws less than 1 a current maximum. the part can be set into shutdown mode using the en pin (en = low). the enable pin cannot be left floating. there are no predefined internal states, so leaving this pin open will cause the part to operate incorrectly. pwm dimming the sp712x drivers allow led-dimming control by applying pwm signaling to en pin. the acceptable frequency range of this signal is 100hz to 20 khz. the minimum on time that is required for the enable pin is 15 s. thus for a 2khz pwm signal, the acceptable duty cycle range is 3% to 100%. to find the minimum pwm duty cycle the following steps are needed: step 1: determine the time period of the pwm frequency where pwm f is the pwm frequency step 2: take the minimum enable on time; this is 15 s for the sp712x parts example for a 2khz signal the minimum duty cycle for the pwm signal is %minimum duty cycle = 3% fault operation if one of leds is shorted, the voltage across the sp712x for that led pin will be vcc, but that channel will still provide the nominal current value thus increasing power dissipation. if all channels are shorted, excessive power dissipation may damage the device. if an led is open, the led pin voltage will be pulled up to vcc, and led current will be reduced to 3ma for the other channels. jun29-07 revd SP7120/22 low dropout led driver ? 2007 sipex corporation page 5 application circuits powering 1 high power led i out up to 75ma with c version powering 1 high power led i out up to 50ma with c version sp7122 powering 3 led?s SP7120 powering 2 leds c1 1nf c1 1nf jun29-07 revd SP7120/22 low dropout led driver ? 2007 sipex corporation page 6 board layout and grounding to obtain the best performance from the sp712x, a p rinted circuit board with ground plane is required. high quality, low series resistance ceram ic 1nf bypass capacitors should be used at the vcc and gnd pins. this capacitor must be locate d as close to the pins as possible. the traces connecting the pins and these capacitors mus t be kept short and should be made as wide as possible. typical performance SP7120a the quiescent current is part of the total output c urrent i out is for 2 channels 15ma per channel i out is for 2 channels 15ma per channel i out is for 2 channels 15ma per channel i out is for 2 channels 15ma per channel jun29-07 revd SP7120/22 low dropout led driver ? 2007 sipex corporation page 7 typical performance SP7120a the quiescent current is part of the total output c urrent i out is for 2 channels 15ma per channel i out is for 2 channels 15ma per channel i out is for 2 channels 15ma per channel i out is for 2 channels 15ma per channel i out is for 2 channels 15ma per channel i out is for 2 channels 15ma per channel jun29-07 revd SP7120/22 low dropout led driver ? 2007 sipex corporation page 8 typical performance SP7120a pwm minimum duty cycle 15 s 20khz ch1: pwm signal ch2 anode of led ch4: led current 10ma/div pwm low duty cycle 15 s 5khz ch1: pwm signal ch2: anode of led ch4: led current 10ma/div jun29-07 revd SP7120/22 low dropout led driver ? 2007 sipex corporation page 9 typical performance SP7120a typical performance sp7122a the quiescent current is part of the total output c urrent i out is for 3 channels 15ma per channel i out is for 3 channels 15ma per channel pwm high duty cycle 20khz ch1: pwm signal ch2: anode of led ch4: led current 10ma/div pwm 50% duty cycle 5khz ch1: pwm signal ch2: anode of led ch4: led current 10ma/div jun29-07 revd SP7120/22 low dropout led driver ? 2007 sipex corporation page 10 typical performance sp7122a i out is for 3 channels 15ma per channel i out is for 3 channels 15ma per channel i out is for 3 channels 15ma per channel i out is for 3 channels 15ma per channel i out is for 3 channels 15ma per channel i out is for 3 channels 15ma per channel jun29-07 revd SP7120/22 low dropout led driver ? 2007 sipex corporation page 11 typical performance sp7122a the quiescent current is part of the total output c urrent i out is for 3 channels 15ma per channel i out is for 3 channels 15ma per channel 50% duty cycle 5khz pwm ch1: pwm signal ch2: anode of led ch4: led current 10ma/div low duty cycle 5khz ch:1 pwm signal ch2: anode of led ch4: led current 10ma/div minimum on time 15 s 20khz pwm ch1: pwm signal ch2: anode of led ch4: led current 10ma/div high duty cycle 20khz ch1: pwm signal ch2: anode of led ch4: led current 10ma/div jun29-07 revd SP7120/22 low dropout led driver ? 2007 sipex corporation page 12 typical performance sp7122a pwm 50% duty cycle single led 5khz ch1: pwm signal ch2 anode of led ch4: led current 20ma/div pwm low duty cycle single led 5khz ch1: pwm signal ch2 anode of led ch4: led current 20ma/div pwm minimum on time 15 s single led 20khz ch1: pwm signal ch2 anode of led ch4: led current 20ma/div pwm 50% single led 20khz ch1: pwm signal ch2 anode of led ch4: led current 20ma/div jun29-07 revd SP7120/22 low dropout led driver ? 2007 sipex corporation page 13 typical performance sp7122b the quiescent current is part of the total output c urrent i out is for 3 channels 20ma per channel i out is for 3 channels 20ma per channel i out is for 3 channels 20ma per channel i out is for 3 channels 20ma per channel i out is for 3 channels 20ma per channel i out is for 3 channels 20ma per channel jun29-07 revd SP7120/22 low dropout led driver ? 2007 sipex corporation page 14 typical performance sp7122b i out is for 3 channels 20ma per channel i out is for 3 channels 20ma per channe pwm minimum on time 15 s 20khz ch1: pwm signal ch2: anode of led ch4: led current 10ma/div pwm high duty cycle 20khz ch1: pwm signal ch2: anode of led ch4: led current 10ma/div pwm 50%duty cycle 5khz ch1: pwm signal ch2 anode of led ch4: led current 10ma/div pwm low duty cycle 5khz ch1: pwm signal ch2 anode of led ch4: led current 10ma/div jun29-07 revd SP7120/22 low dropout led driver ? 2007 sipex corporation page 15 typical performance sp7122b pwm 50% duty cycle single led 5khz ch1: pwm signal ch2 anode of led ch4: led current 50ma/div pwm low duty cycle single led 5khz ch1: pwm signal ch2 anode of led ch4: led current 50ma/div pwm 50% duty cycle single led 20khz ch1: pwm signal ch2 anode of led ch4: led current 50ma/div pwm minimum duty cycle 15us single led 20khz ch1: pwm signal ch2 anode of led ch4: led current 50ma/div jun29-07 revd SP7120/22 low dropout led driver ? 2007 sipex corporation page 16 package: 6 pin sot23 jun29-07 revd SP7120/22 low dropout led driver ? 2007 sipex corporation page 17 ordering information pack quantity is 2500 for sot23-6 tape and reel. for further assistance: email: sipexsupport@sipex.com www support page: http://www.sipex.com/content.aspx?p=support sipex application notes: http://www.sipex.com/applicationnotes.aspx sipex corporation headquarters and sales office 233 south hillview drive milpitas, ca95035 tel: (408) 934-7500 fax: (408) 935-7600 sipex corporation reserves the right to make change s to any products described herein. sipex does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others. part number temp range package type rohs/ lead free output current per channel # of channels ja (?c/w) moisture sensitivity level SP7120aek-l/tr -40c to +85c sot23-6 yes 15ma 2 190 l1 @ 260oc SP7120bek-l/tr -40c to +85c sot23-6 yes 20ma 2 190 l1 @ 260oc SP7120cek-l/tr -40c to +85c sot23-6 yes 25ma 2 190 l1 @ 260oc sp7122aek-l/tr -40c to +85c sot23-6 yes 15ma 3 190 l1 @ 260oc sp7122bek-l/tr -40c to +85c sot23-6 yes 20ma 3 190 l1 @ 260oc sp7122cek-l/tr -40c to +85c sot23-6 yes 25ma 3 190 l1 @ 260oc solved by tm |
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