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ppmic bu www.belling.com.cn BL9580 rev 1.7 belling proprietary in formation. unauthorized photoc opy and duplication prohibited 5/2010 ?2010 belling all rights reserved 1 BL9580 36v, 1.4a step-down high brightness led driver with internal switch features z simple low parts count z internal 36v ndmos switch z up to 1.4a output current z single pin on/off and brightness control using dc voltage or pwm z soft start z high efficiency (up to 97%) z wide input voltage range: 6v to 36v z output shutdown z up to 1mhz switching frequency z inherent open-circuit led protection z typical 3% output current accuracy z high-side current sense z hysteretic control: no compensation z adjustable constant led current z over temperature protection z pb-free sot89-5 and sop-8 packages applications z low voltage halogen replacement leds z automotive lighting z low voltage industrial lighting z led back-up lighting z illuminated signs z lcd tv backlighting description the BL9580 is a continuous mode inductive step-down converter, designed for driving single or multiple series connected leds efficiently from a voltage source higher than the led voltage. the device operates from an input supply between 6v and 36v and provides an externally output current up to 1.4a. depending upon supply voltage and external components, this can provides up to 24 watts of output power. the BL9580 includes the output switch and a high-side output current sensing circuit, which uses an external resistor to set the nominal average output current. output current can be adjusted by applying an external control signal to the 'adj' pin. the adj pin will accept either a dc voltage or a pwm waveform. during dc dimming, this will provide a continuous output current that is proportional to the external applied dc voltage. during the pwm dimming, this will provide a gated output current and the average current is proportional to the duty cycle. applying a voltage of 0.2v or lower to the adj pin turns the output off and switches the device into a low current standby state. ordering information BL9580 x xxx typical application v in i sense lx adj gnd BL9580 n/c gnd v in (6v-36v) c1 4.7uf rs 0.1ohm d1 l1 47uh package: srn: sot89-5 sp8:sop8 features: p: standard (default, lead free) c: customized
ppmic bu www.belling.com.cn BL9580 rev 1.7 belling proprietary in formation. unauthorized photoc opy and duplication prohibited 5/2010 ?2010 belling all rights reserved 2 BL9580 36v, 1.4a step-down high brightness led driver with internal switch absolute maximum rating (note 1) i nput supply voltage (v in ) -0.3v to +40v i sense voltage (v isense ) +0.3v to -5v (note2) lx output voltage (v lx ) -0.3v to +40v adjust pin input voltage (v adj ) -0.3v to +6v switch output current (i lx ) 1.7a maximum junction temperature 150c operating temperature range (note3) -40c to 125c storage temperature range -55c to 150c lead temperature (soldering, 10s) 300c package information thermal resistance (note 5) : package ? ja ? jc sot89-5 160 c/w 45c/w sop-8 153 c/w 39c/w note 1: absolute maximum ratings are those values bey ond which the life of a device may be impaired. note 2: v isense measured respect to v in note 3: the BL9580 is guaranteed to meet perfo rmance specifications from 0c to 70 c. specifications over the ?40c to 125c operating temperature range are assured by de sign, characterization and correlation with statistical process controls. note 4: the first row printed BL9580, the second row printed a y w w. y: year of wafer manufacturing w: week of wafer manufacturing. y 9 a b c d year 2009 2010 2011 2012 2013 w w 01 ? 25 26 27 ? 51 52 week 1 ? 25 26 27 ? 51 52 note 5: thermal resistance is specified with approximately 1 square of 1 oz copper. 1 2 3 5 4 sot89-5 top view adj gnd lx v in i sense marking part number top mark temp range BL9580 BL9580 (note4) a y w w -40c to +125c
ppmic bu www.belling.com.cn BL9580 rev 1.7 belling proprietary in formation. unauthorized photoc opy and duplication prohibited 5/2010 ?2010 belling all rights reserved 3 BL9580 36v, 1.4a step-down high brightness led driver with internal switch pin description pin sot89-5 sop-8 note 6 name function 3 7 lx drain of ndmos switch 2 6 gnd ground (0v) 1 5 adj multi-function on/off and brightness control pin: ? leave floating for normal operation. ? drive to voltage below 0.2v to turn off output current ? drive with dc voltage (0.3v < v adj < 1.2v) to adjust output current from 25% to 100% of i outnom. if the adj voltage is larger than 1.2v, the output current is i outnom . ? drive with pwm signal from open-collector or open-drain transistor, to adjust output current. ? connect a capacitor from this pin to ground to activate soft- start. (soft-start time is approx.0.06ms/nf) 5 4 i sense connect resistor r s from this pin to v in to define nominal average output current i outnom =0.1/r s 4 3 v in input voltage (6v to 3 6 v). decouple to ground with 4.7uf or higher x7r ceramic capacitor close to device 2 pgnd power ground. note 6: pin1, pin8: nc(not connected) for sop-8 package. block diagram voltage regulator gnd adj c1 4.7u f v in i sense lx v in 1moh m 5v 1.2v r 3 r2 r1 rs l1 d1 ot p uvlo 0.2 v adj mn bandga p
ppmic bu www.belling.com.cn BL9580 rev 1.7 belling proprietary in formation. unauthorized photoc opy and duplication prohibited 5/2010 ?2010 belling all rights reserved 4 BL9580 36v, 1.4a step-down high brightness led driver with internal switch electrical characteristics (note 7) (test conditions: v in =12v, t a = 25c, unless otherwise noted.) symbol parameter conditions min typ max unit v in input voltage 6 36 v v uvlo under voltage lock out v in rising 5.07 v v uvlo(hys) uvlo hysteresis v in falling 4.87 v i q(off) quiescent supply current with output off adj pin grounded 50 100 a i q(on) quiescent supply current with output switching adj pin floating f=250khz 1.8 50 ma v isense mean current sense threshold voltage measure on i sense pin with respect to v in 97 100 103 mv v sense(hys) sense threshold hysteresis 15 % i sense i sense pin input current v isense =v in -0.1 1.2 10 ? v adj adj pin floating voltage adj pin floating 5 v i adj adj pin leakage current adj pin grounded 5 ? r adj adj pin pull up resistor to internal supply voltage 1 m v adj(off) dc voltage on adj pin to switch device from active (on) state to quiescent (off) state v adj falling . 0.15 0.2 0.25 v v adj(on) dc voltage on adj pin to switch device from quiescent (off) state to active (on) state v adj rising 0.2 0.25 0.3 v v adj(h) digital dimming adj pin input voltage high 1.5 v v adj(l) digital dimming adj pin input voltage low 0.2 v v adj(dc) dc brightness control 0.3 1.2 v f adj recommended digital dimming frequency 0.1 20 khz duty cycle range of pwm signal applied to adj pin during low frequency pwm dimming mode f adj =100hz 0.1 100 % d pwm(lf) brightness control range 1000:1 duty cycle range of pwm signal applied to adj pin during high frequency pwm dimming mode f adj =10khz 5 100 % d pwm(hf) brightness control range 20:1 r lx lx switch on resistance 0.35 0.7 i lx(leak) lx switch leakage 0.1 5 ?
ppmic bu www.belling.com.cn BL9580 rev 1.7 belling proprietary in formation. unauthorized photoc opy and duplication prohibited 5/2010 ?2010 belling all rights reserved 5 BL9580 36v, 1.4a step-down high brightness led driver with internal switch electrical characteristics (continued) (test conditions: v in =12v, t a = 25c, unless otherwise noted.) symbol parameter conditions min typ max unit i lx(mean) continuous lx switch current 1.4 a t en, delay chip enable delay time the delay time between adj pin rising edge and lx pin falling edge 480 ns t enb, delay chip disable delay time the delay time between adj pin falling edge and lx pin rising edge 25 ns f lx(max) recommended maximum operating frequency 1 mhz t otp over temperature protection threshold temperature rising 160 c t sd(hys) over temperature protection hysteresis temperature falling 20 c note 7: 100% production test at +25c. s pecifications over the temperature range are guaranteed by design and characterization.
ppmic bu www.belling.com.cn BL9580 rev 1.7 belling proprietary in formation. unauthorized photoc opy and duplication prohibited 5/2010 ?2010 belling all rights reserved 6 BL9580 36v, 1.4a step-down high brightness led driver with internal switch typical performance characteristics (test conditions: v in =12v, r s =0.1 , t a = 25c, unless otherwise noted.) 5 1015202530 80 85 90 95 100 efficiency(%) supply voltage v in (v) 1led 2led 3led 4led 5led efficiency vs. supply voltage l=33uh 5 1015202530 -5 -4 -3 -2 -1 0 1 2 3 4 5 deviation from nominal set current(%) supply voltage v in (v) 1led 2led 3led 4led 5led 6led output current variation vs. supply voltage l=33uh 5 1015202530 0 50 100 150 200 250 300 350 400 450 500 550 600 freq(khz) supply voltage v in (v) 1led 2led 3led 4led 5led 6led operating frequency vs. input voltage l=33uh 5 1015202530 0 10 20 30 40 50 60 70 80 90 100 duty cycle(%) supply voltage v in (v) 1led 2led 3led 4led 5led 6led duty cycle vs. input voltage l=33uh 5 1015202530 0.95 0.96 0.97 0.98 0.99 1.00 1.01 1.02 1.03 1.04 1.05 output current(a) supply voltage v in (v) 1led 2led 3led 4led 5led 6led output current vs.supply voltage l=33uh 5 1015202530 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 deviation from nominal set current(%) supply voltage v in (v) 1led 2led 3led 4led 5led 6led output current variation vs. supply voltage l=47uh
ppmic bu www.belling.com.cn BL9580 rev 1.7 belling proprietary in formation. unauthorized photoc opy and duplication prohibited 5/2010 ?2010 belling all rights reserved 7 BL9580 36v, 1.4a step-down high brightness led driver with internal switch 5 1015202530 0 50 100 150 200 250 300 350 400 450 500 550 600 freq(khz) supply voltage v in (v) 1led 2led 3led 4led 5led 6led operating frequency vs. supply voltage l=47uh 5 1015202530 0 10 20 30 40 50 60 70 80 90 100 duty cycle(%) supply voltage vin(v) 1led 2led 3led 4led 5led 6led duty cycle vs. supply voltage l=47uh 5 1015202530 0.94 0.96 0.98 1.00 1.02 1.04 1.06 1.08 output current(a) supply voltage v in (v) 1led 2led 3led 4led 5led 6led output current vs. supply voltage l=47uh 5 1015202530 -5 -4 -3 -2 -1 0 1 2 3 4 5 deviation from set nominal set current(%) supply voltage v in( v) 1led 2led 3led 4led 5led 6led output current variation vs. supply voltage l=100uh 5 1015202530 0 50 100 150 200 250 300 freq(khz) supply voltage v in (v) 1led 2led 3led 4led 5led 6led operating frequency vs. supply voltage l=100uh 5 1015202530 0 10 20 30 40 50 60 70 80 90 100 duty cycle(%) supply voltage v in (v) 1led 2led 3led 4led 5led 6led duty cycle vs.supply voltage l=100uh
ppmic bu www.belling.com.cn BL9580 rev 1.7 belling proprietary in formation. unauthorized photoc opy and duplication prohibited 5/2010 ?2010 belling all rights reserved 8 BL9580 36v, 1.4a step-down high brightness led driver with internal switch 5 1015202530 0.96 0.97 0.98 0.99 1.00 1.01 1.02 output current(a) supply voltage v in (v) 1led 2led 3led 4led 5led 6led output current vs. supply voltage l=100uh 0 5 10 15 20 25 30 0 1 2 3 4 5 6 v adj (v) supply voltage v in (v) v adj vs. supply voltage l=33uh 0 5 10 15 20 25 30 0 50 100 150 200 250 supply current(ua) supply voltage v in (v) supply current vs. supply voltage l=33uh 0 5 10 15 20 25 30 0 10 20 30 40 50 60 shutdown current(ua) supply voltage v in (v) shutdown current vs. supply voltage 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 led current(a) adj pin voltage(v) led current vs. v adj -50 0 50 100 150 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 "on" resistance( ) ambient temperature( c) lx switch "on" resistance vs. temperature
ppmic bu www.belling.com.cn BL9580 rev 1.7 belling proprietary in formation. unauthorized photoc opy and duplication prohibited 5/2010 ?2010 belling all rights reserved 9 BL9580 36v, 1.4a step-down high brightness led driver with internal switch -50 -25 0 25 50 75 100 125 150 4.75 4.80 4.85 4.90 4.95 5.00 adj pin voltage(v) ambient temperature( c) 12v, single led, r s =0.15 12v, three led,r s =0.33 24v, single led,r s =0.15 24v, three led,r s =0.33 v adj vs.temperature l=47uh -50 -25 0 25 50 75 100 125 150 96 100 104 108 112 v sense (mv) ambient temperature( c) 12v, single led, r s =0.15 12v, three led, r s =0.33 24v, single led, r s =0.15 24v, three led, r s =0.33 voltage across r sense vs. temperature l=47uh -50 -25 0 25 50 75 100 125 150 -4 0 4 8 12 deviation from nominal set value(%) ambient temperature( c) 12v, single led, r s =0.15 12v, three led, r s =0.33 output current change vs. temperature l=47uh -50 -25 0 25 50 75 100 125 150 -4 0 4 8 12 deviation from nominal set value(%) ambient temperature( c) 24v, single led, r s =0.15 24v, three led, r s =0.33 output current change vs. temperature l=47uh
ppmic bu www.belling.com.cn BL9580 rev 1.7 belling proprietary in formation. unauthorized photoc opy and duplication prohibited 5/2010 ?2010 belling all rights reserved 10 BL9580 36v, 1.4a step-down high brightness led driver with internal switch operation description the device, in conjunction with the coil (l1) and current sense resistor (r s ), forms a self oscillating continuous-mode buck converter. when input voltage v in is first applied, the initial current in l1 and r s is zero and there is no output from the current sense circuit. under this condition, the (-) input to the comparator is at ground and its output is high. this turns on an internal switch and switches the lx pin low, causing current to flow from v in to ground, via r s , l1 and the led(s). the current rises at a rate determined by v in and l1 to produce a voltage ramp (v isense ) across r s . when (v in -v isense ) > 115mv, the output of comparator switches low and the switch turns off. the current flowing on the r s decreases at another rate. when (v in - v isense ) < 85mv, the switch turns on again and the mean current on the led is determined by 85 115 ( ) / 100 / 2 ss mv r mv r + = the high-side current-sensing scheme and on-board current-setting circuitry minimize the number of exter nal components while delivering led current with 3% accuracy, using a 1% sense resistor. the BL9580 allows dimming with a pwm signal at the adj input. a logic level below 0.2v at adj forces BL9580 to turn off the led and the logic leve l at adj must be at least 1.2v (1.5v recommended) to turn on the full led current. the frequency of pwm dimming ranges from 100hz to more than 20 khz. the adj pin can be driven by an external dc voltage (v adj ) to adjust the output current to a value below the nominal average value defined by r s . the dc voltage is valid from 0.3v to 1.2v. when the dc voltage is higher than 1.2v, the output current keeps constant. the led current also can be adj usted by a resistor connected to the adj pin. an internal pull- up resistor (typical 1.0 m ? ) is connected to a 5v internal regulator. the voltage of adj pin is divided by the internal and external resistor. the adj pin is pulled up to the internal regulator (5v) by a 1.0 m ? resistor. it can be floated at normal working. when a voltage applied to adj falls below the threshold (0.2v nom.), the output switch is turned off. the internal regulator and voltage reference remain powered during shutdown to provide the reference for the shutdown circuit. quiescent supply current during shutdown is nominally 50ua and switch leakage is below 5ua. additionally, to ensure the reliability, the BL9580 is built with a thermal shutdown (tsd) protection and a thermal pad. the tsd protests the ic from over temperature (160 ). also the thermal pad enhances power dissipation. as a result, the BL9580 can handle a large amount of current safely. application information setting nominal average output current with external resistor r s the nominal average out put current in the led(s) is determined by the value of the external current sense resistor (r s ) connected between v in and i sense and is given by: 0.1 out s i r = this equation is valid wh en adj pin is float
ppmic bu www.belling.com.cn BL9580 rev 1.7 belling proprietary in formation. unauthorized photoc opy and duplication prohibited 5/2010 ?2010 belling all rights reserved 11 BL9580 36v, 1.4a step-down high brightness led driver with internal switch or applied with a voltage higher than 1.2v (must be less than or equal to 5v). actually, r s sets the maximum average current which can be adjusted to a less one by dimming. the table below gives values of nominal average output current for several preferred values of cu rrent setting resistor (r s ) in the typical application circuit shown on page 1. nominal average output current (ma) r s ( ) 1000 0.1 760 0.13 667 0.15 333 0.3 output current adjustment by external dc control the adj pin can be driven by an external dc voltage (v adj ), as shown, to adjust the output current to a value below the nominal average value defined by r s . u1 BL9580 vin isense lx adj gnd rs l1 47uh 1 2 d1 1 2 cin 4.7uf vadj vin the average output current is given by: 0.1 (0.3 1.2 ) 1.2 adj out adj s v i vv v r =? note that 100% brightness setting corresponds to: (1.3v v adj 5v) output current adjustment by pwm control a pulse width modulated (pwm) signal with duty cycle pwm can be applied to the adj pin, as shown bel ow, to adjust the output current to a value below the nominal average value set by resistor r s : 0.1 (0 100%,1.2 5 ) out adj s d i dvvv r =? ? 0.1 (0 100%, 0.3 1.2 ) 1.2 pulse out pulse s vd idvvv r =??? u1 BL9580 vin isense lx adj gnd l1 47uh 1 2 rs d1 1 2 cin 4.7uf vin pwm pwm dimming provides reduced brightness by modulating the led?s forward current between 0% and 100%. the led brightness is controlled by adjusting the relative ratios of the on time to the off time. a 25% brightness level is achieved by turning the led on at full current for 25% of one cycle. to ensure this switching process between on and off state is invisible by human eyes, the switching frequency must be greater than 100 hz. above 100 hz, the human eyes average the on and off times, seeing only an effective brightness that is proportional to the led?s on-time duty cycle. the advantage of pwm dimming is that the forward current is always constant;
ppmic bu www.belling.com.cn BL9580 rev 1.7 belling proprietary in formation. unauthorized photoc opy and duplication prohibited 5/2010 ?2010 belling all rights reserved 12 BL9580 36v, 1.4a step-down high brightness led driver with internal switch therefore the led colo r does not vary with brightness as it does with analog dimming. pulsing the current provides precise brightness control while preserving the color purity. the dimming frequency of BL9580 can be as high as 20 khz. shutdown mode taking the adj pin to a voltage below 0.2v will turn off the output and the supply current will fall to a low standby level of 50 a nominal. soft-start an external capacitor from the adj pin to ground will provide soft-start delay, by increasing the time ta ken for the voltage on this pin to rise to the turn-on threshold. adding capacitance increases this delay by approximately 0.06ms/nf. inherent open-circ uit led protection if the connection to the led(s) is open- circuited, the coil is isolated from the lx pin of the chip, so the device will not be damaged. capacitor selection a low esr capacitor should be used for input decoupling, as the esr of this capacitor appears in series with the supply source impedance and lowers overall efficiency. this capacitor has to supply the relatively high peak cu rrent to the coil and smooth the current ripple on the input supply. a minimum value of 4.7uf is acceptable if the input source is close to the device, but higher values will improve performance at lower input voltages, especially when the source impedance is high. the input capacit or should be placed as close as possible to the ic. for maximum stability over temperature and voltage, capacitors with x7r, x5r, or better dielectric are recommended. cap- acitors with y5v dielectr ic are not suitable for decoupling in this application and should not be used. a suitable murata capacitor would be grm42-2x7r475k-50. the following web sites are useful when finding alternatives: www.murata.com www.t-yuden.com www.avxcorp.com inductor selection recommended inductor values for the BL9580 are in the range 27uh to 100uh. higher values of inductance are re- commended at lower out put current in order to minimize errors due to switching delays, which result in increased ripple and lower efficiency. higher values of in- ductance also result in a smaller change in output current over the supply voltage range. the inductor should be mounted as close to the device as possible with low resistance connections to the lx and v in pins. the chosen coil should have a saturation current higher than the peak output current and a continuous current rating above the required mean output current. suitable coils for use with the BL9580 are listed in the table below: part no. l (uh) dcr ( ) i sat (a) manufacturer mss1038- 333 33 0.093 2.3 mss1038- 473 47 0.128 2 mss1038- 683 68 0.213 1.6 mss1038- 104 100 0.304 1.3 coilcraft www.coilcraft.com
ppmic bu www.belling.com.cn BL9580 rev 1.7 belling proprietary in formation. unauthorized photoc opy and duplication prohibited 5/2010 ?2010 belling all rights reserved 13 BL9580 36v, 1.4a step-down high brightness led driver with internal switch the inductor value should be chosen to maintain operating duty cycle and switch 'on'/'off' times within the specified limits over the supply voltage and load current range. the following equations can be used as a guide. lx switch 'on' time () on in led avg s l lx li t vv i rrr = ??++ lx switch 'off' time () off led d avg s l li t vvirr = ++ + where: l is the coil inductance (h) r l is the coil resistance ( ? ) r s is the current sense resistance ( ? ) i avg is the required led current (a) i is the coil peak-peak ripple current (a) (internally set to 0.3 x i avg ) v in is the supply voltage (v) v led is the total led forward voltage (v) r lx is the switch resistance ( ? ) (=0.35 ? nominal) v d is the diode forward voltage at the required load current (v) diode selection for maximum efficiency and performance, the rectifier (d1) should be a fast low capacitance schottky diode with low reverse leakage at the maximum operating voltage and temperature. they also provide better efficiency than silicon diodes, due to a combination of lower forward voltage and reduced recovery time. it is important to select parts with a peak current rating above the peak coil current and a continuous current rating higher than the maximum output load current. it is very important to consider the reverse leakage of the diode when oper ating above 85c. excess leakage will increase the power dissipation in the device and if close to the load may create a thermal runaway condition. the higher forward voltage and overshoot due to reverse recovery time in silicon diodes will increase the peak voltage on the lx output. if a silicon diode is used, care should be taken to ensure that the total volt age appearing on the lx pin including supply ripple, does not exceed the specified maximum value. the following web sites are useful when finding alternatives: www.onsemi.com reducing output ripple peak to peak ripple current in the led(s) can be reduced, if re quired, by shunting a capacitor c led across the led(s) as shown below: u1 BL9580 vin isense lx adj gnd rs l1 47uh 1 2 d1 1 2 cin 4.7uf vin cled 1uf a value of 1uf will reduce the supply ripple current by a factor three (approx.). proportionally lower ripple can be achieved with higher capacitor va lues. note that the capacitor will not affect operating fre- quency or efficiency, but it will increase start-up delay and reduce the frequency of
ppmic bu www.belling.com.cn BL9580 rev 1.7 belling proprietary in formation. unauthorized photoc opy and duplication prohibited 5/2010 ?2010 belling all rights reserved 14 BL9580 36v, 1.4a step-down high brightness led driver with internal switch dimming, by reducing the rate of rise of led voltage. by adding this capacitor the current waveform through the led(s) changes from a triangular ramp to a more sinusoidal version without altering the mean current value. operation at low supply voltage the internal regulator disables the drive to the switch until the supply has risen above the startup threshold (v uvlo ). above this threshold, the device will start to operate. however, with the suppl y voltage below the specified minimum val ue, the switch duty cycle will be high and the device power dissipation will be at a maximum. care should be taken to avoid operating the device under such conditions in the application, in order to minimize the risk of exceeding the maximum allowed die temperature. (see next section on thermal considerations). the dr ive to the switch is turned off when the supply voltage falls below the under-voltage threshold (v uvlo - 0.2v). this prevents the switch working with excessive 'on' resistance under conditions where the duty cycle is high. thermal considerations when operating the device at high ambient temperatures, or when driving maximum load current, care must be taken to avoid exceeding the package power dissipation limits. the graph below gives details for power derating. this assumes the device to be mounted on a 25mm 2 pcb with 1oz copper standing in still air. note that the device power dissipation will most often be a ma ximum at minimum supply voltage. it will also increase if the efficiency of the circuit is low. this may result from the use of unsuitable coils, or excessive parasitic out put capacitance on the switch output. -40 -20 0 20 40 60 80 100 120 140 0 200 400 600 800 1000 1200 1400 1600 power(mw) ambient temperature max. power dissipation thermal compensation of output current high luminance leds often need to be supplied with a temperature compensated current in order to maintain stable and reliable operation at all drive levels. the leds are usually mounted remotely from the device, so internal circuits for the BL9580 have been optimized to minimize the change in output current when no compensation is employed. if output current compensation is required, it is possible to use an external temperature sensing network - normally using negative temperature coefficien t (ntc) thermistors and/or diodes, mounted very close to the led(s). the output of the sensing network can be used to drive the adj pin in order to reduce output current with increasing temperature. thermal shutdown protection to ensure the reliability, the BL9580 is built with a thermal shutdown (tsd) protection function. the tsd protests the ic from over temperature (160 ). when the chip
ppmic bu www.belling.com.cn BL9580 rev 1.7 belling proprietary in formation. unauthorized photoc opy and duplication prohibited 5/2010 ?2010 belling all rights reserved 15 BL9580 36v, 1.4a step-down high brightness led driver with internal switch temperature decreases (140 ), the ic recovers again. layout considerations careful pcb layout is critical to achieve low switching losses and stable operation. use a multilayer board whenever possible for better noise immunity. minimize ground noise by connecting high-current ground returns, the input bypass-capacitor ground lead, and the output-filter ground lead to a single point (star ground configuration). lx pin the lx pin of the device is a fast switching node, so pcb tracks should be kept as short as possible. to minimize ground 'bounce', the ground pin of the device should be soldered dire ctly to the ground plane. coil and decoupling capacitors and current sense resistor it is particularly important to mount the coil and the input decoupling capacitor as close to the device pins as possible to minimize parasitic resistance and inductance, which will degrade efficiency. it is also important to minimize any track resistance in series with current sense resistor r s . it?s best to connect v in directly to one end of r s and i sense directly to the opposite end of r s with no other currents flowing in these tracks. it is important that the cathode current of the schottky diode does not flow in a track between r s and v in as this may give an apparent higher measure of current than is actual because of track resistance. adj pin the adj pin is a high impedance input, so when left floating, pcb traces to this pin should be as short as possible to reduce noise pickup. adj pin can also be connected to a voltage between 1.2v~5v. in this case, the internal circuit will clamp the output current at the value which is set by adj=1.2v. high voltage traces avoid running any high voltage traces close to the adj pin, to reduce the risk of leakage due to board contamination. any such leakage may raise the adj pin voltage and cause excessive output current. a ground ring placed around the adj pin will minimize changes in output current under these conditions.
ppmic bu www.belling.com.cn BL9580 rev 1.7 belling proprietary in formation. unauthorized photoc opy and duplication prohibited 5/2010 ?2010 belling all rights reserved 16 BL9580 36v, 1.4a step-down high brightness led driver with internal switch package description dimensions in millimeters dimensions in inches symbol min max min max a 1.397 1.600 0.055 0.063 b 0.356 0.508 0.014 0.020 b1 0.406 0.533 0.016 0.021 b 2.388 2.591 0.094 0.102 c 3.937 4.242 0.155 0.167 c1 0.787 1.194 0.031 0.047 d 4.394 4.597 0.173 0.181 d1 1.397 1.702 0.055 0.067 e 1.500 typ. 0.060 typ. h 0.356 0.432 0.014 0.017 sot89-5 surface mount package
ppmic bu www.belling.com.cn BL9580 rev 1.7 belling proprietary in formation. unauthorized photoc opy and duplication prohibited 5/2010 ?2010 belling all rights reserved 17 BL9580 36v, 1.4a step-down high brightness led driver with internal switch dimensions in millimeters dimensions in inches symbol min max min max a 4.80 5.00 0.188 0.197 b 3.80 4.00 0.149 0.158 c 5.80 6.20 0.228 0.244 d 1.27 bsc 0.050 e 0.33 0.51 0.013 0.020 f 0.10 0.25 0.004 0.010 h 1.35 1.75 0.053 0.069 k 0.19 0.25 0.007 0.010 m 0.40 1.27 0.016 0.050 0o 8o 0o 8o sop-8 surface mount package

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