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?004 fairchild semiconductor corporation 1 www.fairchildsemi.com a ugust 2005 f an5331 rev. 1.0.1 f an5331 high ef?iency serial led driver and oled supply with 20v integrated switch f an5331 high ef?iency serial led driver and oled supply with 20v integrated switch features 1.6mhz switching frequency low noise low r ds(on) : 0.5 ? adjustable output voltage 1a peak switch current 1w output power capability low shutdown current: <1? cycle-by-cycle current limit over-voltage protection fixed-frequency pwm operation internal compensation 5-lead sot-23 package applications cell phones pdas handheld equipment display bias led bias description the FAN5331 is a general purpose, ?ed-frequency boost con- ve r ter designed to operate at high switching frequencies in order to minimize switching noise measured at the battery ter- minal of hand-held communications equipment. quiescent cur- rent in normal mode of operation as well as in shutdown mode is designed to be minimal in order to extend battery life. normal mode of operation or shutdown mode can be selected by a logic level shutdown circuitry. the low on-resistance of the internal n-channel switch ensures high ef?iency and low power dissipation. a cycle-by-cycle cur- rent limit circuit keeps the peak current of the switch below a typical value of 1a. the FAN5331 is available in a 5-lead sot- 23 package. t ypical application figure 1. typical application diagram shdn v in v out r1 r2 gnd v in fb sw f an5331 c f c in 10 h 1 3 2 4 5 4.7 f 120pf c out l bat54 4.7 f 2.7v to 5.5v on off
2 www.fairchildsemi.com f an5331 rev. 1.0.1 f an5331 high ef?iency serial led driver and oled supply with 20v integrated switch pin assignment figure 2. pin assignment pin description absolute maximum ratings ( note1) recommended operating conditions notes: 1. stresses above those listed under ?bsolute maximum ratings?may cause permanent damage to the device. this is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. absolute maximum ratings apply individually only, not in combination. 2. using eia/jesd22a114b (human body model) and eia/jesd22c101-a (charge device model). 3. this load capacitance value is required for the loop stability. tolerance, temperature variation, and voltage dependency of the capacitance must be considered. typically a 4.7? ceramic capacitor is required to achieve specified value at v out = 15v. pin no. pin name pin description 1s w switching node. 2 gnd analog and power ground. 3f bf eedback node that connects to an external voltage divider. 4 shdn shutdown control pin. logic high enables, logic low disables the device. 5v in input voltage. p arameter min max unit v in to gnd 6.0 v fb, shdn to gnd -0.3 v in + 0.3 v sw to gnd -0.3 23 v lead soldering temperature (10 seconds) 300 ? j unction temperature 150 ? storage temperature -55 150 ? thermal resistance ( ja ) 265 ?/w electrostatic discharge protection (esd) level (note 2) hbm 2.5 kv cdm 1 p arameter min typ max unit input voltage 2.7 5.5 v output voltage v in 20 v operating ambient temperature -40 25 85 ? output capacitance (note 3) 1.6 ? 5-lead sot-23 top view sw gnd fb shdn v in
3 www.fairchildsemi.com f an5331 rev. 1.0.1 f an5331 high ef?iency serial led driver and oled supply with 20v integrated switch electrical characteristics t est circuit figure 3. test circuit unless otherwise noted, v in = 3.6v, t a = -40? to +85?, typical values are at t a = 25?, test circuit, figure 3. p arameter conditions min. typ. max. units switch current limit v in = 3.2v 0.7 1 a load current capability v out = 15v, v in 2.7v 35 ma v out = 15v, v in 3.2v 50 ma switch on-resistance v in = 5v 0.5 ? v in = 3.6v 0.7 ? quiescent current v shdn = 3.6v, no switching 0.7 ma v shdn = 3.6v, switching 1.6 3.0 ma off mode current v shdn = 0v 0.1 2 a shutdown threshold device on 1.5 v device off 0.5 v shutdown pin bias current v shdn = 0v or v shdn = 5.5v 10 na f eedback voltage i load = 0ma 1.205 1.230 1.255 v f eedback pin bias current 10 na f eedback voltage line regulation 2.7v < v in < 5.5v, i load = 0ma 0.6 1.2 % switching frequency 1.15 1.6 1.85 mhz maximum duty cycle 87 93 % enable delay v in = 2.7v, i out = 35ma, v out = 15v 0.8 5 ms po w er on delay v in = 2.7v, i out = 35ma, v out = 15v 0.8 5 ms switch leakage current no switching, v in = 5.5v 1 a 150k ? 13.4k ? shdn v in v out r1 r2 gnd v in fb sw fa n5331 c f c in 10 h 1 3 2 4 5 4.7 f 120pf c out l bat54 4.7 f 2.7v to 5.5v on off
4 www.fairchildsemi.com f an5331 rev. 1.0.1 f an5331 high ef?iency serial led driver and oled supply with 20v integrated switch t ypical performance characteristics t a = 25?, test circuit figure 3, unless otherwise noted. -50 0 50 100 150 1.21 1.22 1.23 1.24 1.25 temperatu re ( c) vs vf (vin=2.7 v, iload=15ma) temperatu re ( c) vs vf (vin=3.6 v, iload=15ma) temperatu re ( c) vs vf (vin=5.5 v, iload=15ma) 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 14.86 14.88 14.90 14.92 14.94 14.96 14.98 vin(v) vs vout(v) at iload=0ma vi n( v) vs vout(v), at load=10ma vi n( v) vs vout(v), at load=20ma vi n( v) vs vout(v) at iload=30ma vi n( v) vs vout(v) at iload=40ma vi n( v) vs vout(v) at iload=50ma output voltage vs input voltage output voltage (v) i nput voltage (v) 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 0.72 0.74 0.76 0.78 0.80 0.82 0.84 0.86 0.88 0.90 0.92 vi n( v) vs efficiency at iload =10ma vi n( v) vs efficiency at iload =20ma vi n( v) vs efficiency at iload =30ma vi n( v) vs efficiency at iload =40ma vi n( v) vs efficiency at iload =50ma efficiency input voltage (v) efficiency vs input voltage 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 supply current vs input voltage s upply current (ma) input voltage (v) switching non switching -40 -20 0 20 40 6 080 100 12 0140 1.0 1.2 1.4 1.6 1.8 switch ing frequency (mhz) ambient temperature ( c) switching frequency vs ambient temperature i out = 15ma v out = 15v v in = 3.6v feedback voltage vs ambient temperature i out = 15ma ambient temperature ( c) feedback voltage (v) 2.5 3.0 3.5 4.0 4.5 5.0 5.5 0 50 100 150 200 250 300 i out = 0ma 2.5 3.0 3.5 4.0 4.5 5.0 5.5 0 30 60 90 120 150 180 210 maximum load current vs input voltage maximum load current (ma) input voltage (v) v o u t = 1 2 v v o u t = 15 v v o u t = 2 1 v
5 www.fairchildsemi.com f an5331 rev. 1.0.1 f an5331 high ef?iency serial led driver and oled supply with 20v integrated switch t ypical performance characteristics (contd.) t a = 25?, test circuit figure 3, unless otherwise noted. time (20 s/div) (5v/div) st artup after enable time ( 200 s/div) r l = 300 ? v in = 3v (200ma/div) v out = 15v in du ctor current= 0ma line transient response time (100 s/div) output voltage input voltage -0.6 v +0.6v v in = 4.2v v in = 3.2v load transient response i out = 30ma t r = t f = 10 s v out = 15v t r = t f < 1 s v out = 15v i out = 0 to 35ma (10ma/div) (100mv/div) output power spectral density v in = 3.6v i out = 35ma
6 www.fairchildsemi.com f an5331 rev. 1.0.1 f an5331 high ef?iency serial led driver and oled supply with 20v integrated switch block diagram figure 4. block diagram circuit description the FAN5331 is a pulse-width m odulated (pwm) current-mode boost converter. the FAN5331 improves the performance of bat- tery powered equipment by signi?antly minimizing the spectral distribution of noise at the input caused by the switching action of the regulator. in order to facilitate effective noise ?tering, the s witching frequency was chosen to be high, 1.6mhz. an internal soft start circuitry minimizes in-rush currents. the timing of the soft start circuit was chosen to reach 95% of the nominal output voltage within maximum 5ms following an enable command when v in = 2.7v, v out = 15v, i load = 35ma and c out (effective) = 3.2 f. the device architecture is that of a current mode controller with an internal sense resistor connected in series with the n-chan- nel switch. the voltage at the feedback pin tracks the output v oltage at the cathode of the external schottky diode (shown in the test circuit). the error ampli?r ampli?s the difference between the feedback voltage and the internal bandgap refer- ence. the ampli?d error voltage serves as a reference voltage to the pwm comparator. the inverting input of the pwm com- parator consists of the sum of two components: the ampli?d control signal received from the 50m ? current sense resistor and the ramp generator voltage derived from the oscillator. the oscillator sets the latch, and the latch turns on the fet switch. under normal operating conditions, the pwm comparator resets the latch and turns off the fet, thus terminating the pulse. since the comparator input contains information about the out- put voltage and the control loop is arranged to form a negative f eedback loop, the value of the peak inductor current will be adjusted to maintain regulation. every time the latch is reset, the fet is turned off and the cur- rent ?w through the switch is terminated. the latch can be reset by other events as well. over-current condition is moni- tored by the current limit comparator which resets the latch and turns off the switch instantaneously within each clock cycle. over-voltage protection the voltage on the feedback pin is sensed by an ovp compar- ator. when the feedback voltage is 15% higher than the nominal v oltage, the ovp comparator stops switching of the power tran- sistor, thus preventing the output voltage from going higher. applications information setting the output voltage the internal reference is 1.23v (typical). the output voltage is divided by a resistor divider, r1 and r2 to the fb pin. the out- put voltage is given by according to this equation, and assuming desired output volt- age of 15v, good choices for the feedback resistors are, r 1 =150k ? and r 2 =13.4k ? . inductor selection the inductor parameters directly related to device performances are saturation current and dc resistance. the FAN5331 oper- ates with a typical inductor value of 10?. the lower the dc resistance, the higher the ef?iency. usually a trade-off between inductor size, cost and overall ef?iency is needed to make the optimum choice. reference oscillator n fb fb driver over voltage comp comp - - + + s ramp generator r r r q s current limit comparator 0.05 1.15 x v ref shutdown circuitry thermal shutdown shdn gnd sw v in amp error amp 45 1 2 3 + + - - + - soft-start v out v ref 1 r 1 r 2 ------ - + ?? ?? =
7 www.fairchildsemi.com f an5331 rev. 1.0.1 f an5331 high ef?iency serial led driver and oled supply with 20v integrated switch the inductor saturation current should be rated around 1a, which is the threshold of the internal current limit circuit. this limit is reached only during the start-up and with heavy load condition; when this event occurs the converter can shift over in discontinuous conduction mode due to the automatic turn-off of the switching transistor, resulting in higher ripple and reduced ef?iency. some recommended inductors are suggested in the table below: ta b le 1: recommended inductors capacitors selection f or best performance, low esr input and output capacitors are required. ceramic capacitors in the range 4.7? to 10?, placed as close to the ic pins, are recommended for the lower input and output ripple. the output capacitor voltage rating should be according to the v out setting. a feed forward capacitor c f , is required for stability. the recom- mended value (r 1 x c f ) is around 18?. some capacitors are suggested in the table below. ta b le 2: recommended capacitors diode selection the external diode used for recti?ation is usually a schottky diode. its average forward current and reverse voltage maxi- m um ratings should exceed the load current and the voltage at the output of the converter respectively. a barrier schottky diode such as bat54 is preferred, due to its lower reverse current over the temperature range. care should be taken to avoid any short circuit of v out to gnd, ev en with the ic disabled, since the diode can be instantly dam- aged by the excessive current. thermal shutdown when the die temperature exceeds 150?, a reset occurs and will remain in effect until the die cools to 130?, at that time the circuit will be allowed to restart. pcb layout recommendations the inherently high peak currents and switching frequency of power supplies require careful pcb layout design. therefore, use wide traces for high current paths and place the input capacitor, the inductor, and the output capacitor as close as possible to the integrated circuit terminals. the resistor divider that sets the output voltage should be routed away from the inductor to avoid rf coupling. a four layer pcb with at least one g round plane connected to the pin 2 of the ic is recommended. this ground plane acts as an electromagnetic shield to reduce emi and parasitic coupling between components. figure 5. recommended layout application examples 1. led driver one or more serial led strings can be driven with a constant current, set by the series resistor, given by figure 6. low noise boost led driver inductor v alue vendor part number comment 10? panasonic ell6gm100m lower pro?e (1.6mm) 10? murata lqs66sn100m03l highest ef?iency 10? coilcraft do1605t-103mx small size capacitor v alue vendor part number 4.7? panasonic ecj3yb1c475k 4.7? murata grm31cr61c475 i led 1.23v r1 --------------- - = shdn v in v out r1 r2 gnd v in fb sw f an 5331 c in 10 h 1 3 2 4 5 4.7 f c out l bat54 4.7 f 2.7v to 5.5v on off
8 www.fairchildsemi.com f an5331 rev. 1.0.1 f an5331 high ef?iency serial led driver and oled supply with 20v integrated switch the feedback loop tightly regulates the current in the branch connected to fb pin, while the current in the other branch depends on the sum of the led s forward voltages, v out and the ballast resistor. the input and the output ripple is less than 3mv rms , for load currents up to 40ma. a zener diode (v z = 22v) connected between v out and gnd can prevent the FAN5331 from being damaged by over-voltage, if the load is accidently disconnected during operation. 2. dual boost converter a negative voltage can be provided by adding an external charge pump (c1, c2, d2, and d3). figure 7. dual (? boost converter while the feedback loop tightly regulates v out , the negative out- put voltage (-v out ) can supply a light load with a negative volt- age. nevertheless, the negative voltage depends on the changes of the load current in both -v out and +v out , as shown in the graph below. 2.5 3.0 3. 54.04.55.05.56.0 19.7 19.8 19.9 20.0 20.1 20.2 led current (ma) input voltage (v) led current vs input voltage (string connected to fb pin) shdn v in in v out -v out r1 r2 gnd v fb sw f an5331 c f c in 10 h 1 3 2 4 5 4.7 f 120pf c out l bat54 bat54s 4.7 f 2.7v to 5.5v on off c2 c1 d1 d3 d2 4.7 f 0.1 f i out = 10ma i out = 50ma 0102 0304050 -18 -16 -14 -12 -10 negative output voltage vs load current lo ad current on positive output side (ma) negative output voltage (v) -15v/unloaded -15v/10ma load
www. onsemi.com 1 on semiconductor and are trademarks of semiconductor components industries, llc dba on semiconductor or its subsidiaries i n the united states and/or other countries. on semiconductor owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property . a listing of on semiconductor?s product/patent coverage may be accessed at www.onsemi.com/site/pdf/patent ? marking.pdf . on semiconductor reserves the right to make changes without further notice to any products herein. on semiconductor makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does o n semiconductor assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including wi thout limitation special, consequential or incidental damages. buyer is responsible for its products and applications using on semiconductor products, including compliance with all laws, reg ulations and safety requirements or standards, regardless of any support or applications information provided by on semiconductor. ?typical? parameters which may be provided in on semiconductor data sheets and/or specifications can and do vary in dif ferent applications and actual performance may vary over time. all operating parameters, including ?typic als? must be validated for each customer application by customer?s technical experts. on semiconductor does not convey any license under its patent rights nor the right s of others. on semiconductor products are not designed, intended, or authorized for use as a critical component in life support systems or any fda class 3 medical devices or medical devices with a same or similar classification in a foreign jurisdiction or any devices intended for implantation in the human body. should buyer purchase or use on semicondu ctor products for any such unintended or unauthorized application, buyer shall indemnify and hold on semiconductor and its officers, employees, subsidiaries, affiliates, and distrib utors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that on semiconductor was negligent regarding the design or manufacture of the part. on semiconductor is an equal opportunity/affirmative action employer. this literature is subject to all applicable copyright laws and is not for resale in any manner. publication ordering information n. american technical support : 800 ? 282 ? 9855 toll free usa/canada europe, middle east and africa technical support: phone: 421 33 790 2910 japan customer focus center phone: 81 ? 3 ? 5817 ? 1050 www.onsemi.com literature fulfillment : literature distribution center for on semiconductor 19521 e. 32nd pkwy, aurora, colorado 80011 usa phone : 303 ? 675 ? 2175 or 800 ? 344 ? 3860 toll free usa/canada fax : 303 ? 675 ? 2176 or 800 ? 344 ? 3867 toll free usa/canada email : orderlit@onsemi.com on semiconductor website : www.onsemi.com order literature : http://www.onsemi.com/orderlit for additional information, please contact your local sales representative ? semiconductor components industries, llc
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