innovative power tm - 1 - www.active-semi.com copyright ? 2008 active-semi, inc. rev0, 13-may-08 typical application circuit ACT6305 low input high efficiency synchronous step-u p dc/dc converter features ? 1v typical startup voltage ? up to 94% efficiency ? fully integrated power stage ? fixed 3.3v/5v or adjustable output voltage ? nanostandby tm shutdown mode ? tiny sot23-5 package ? rohs compliant package applications ? hand-held devices ? one to three cell battery operated devices ? pdas ? cellular phones ? digital cameras ? gps general description the ACT6305 is a high efficiency synchronous step-up dc/dc converter t hat consumes just 17a of quiescent supply current and is capable of deliv- ering more than 400ma output current using only three external components. this device achieves a typical startup voltage of just 1v, making it ideal for applications operating from 1 or 2 alkaline cells. this device incorporates an internal synchronous rectifier, and achieves ex cellent peak efficiency of up to 94% and features a proprietary control scheme that ensures high efficiency over a wide load current range. the ACT6305 features pin-selectable output volt- ages of 3.3v or 5v, or it can also be set externally to any voltage between 2v and 5v. the ACT6305 is available in a tiny sot23-5 package. ACT6305 c2 22f v out v in enable c1 22f l 6.8h lx en out fb g pb-free efficiency (%) efficiency vs. output current ACT6305-001 output current (ma) 40 60 80 100 0.1 1.0 10 1000 30 v in = 3.5v v in = 1.2v v out = 5v 100 v in = 5v 50 70 90 v in = 2.4v
ACT6305 rev0, 13-may-08 innovative power tm - 2 - www.active-semi.com copyright ? 2008 active-semi, inc. ordering information pin description pin number pin name pin description 1 fb output voltage selection and feedback input. connect this pin to g for v out = 5v, to out for v out = 3.3v. connect fb to a resistor divider to set the output voltage be- tween 2v and 5v. see the output voltage selection section for mo re information. 2 g ground. 3 en shutdown input. drive en to out or to a logic high for normal operation, drive en to g or to a logic low to disable the regulator. 4 lx inductor connection. 5 out output. ACT6305 regulates voltage at this pin. out also provides power to the ic. part number temperature range package pins ACT6305uc-t -40c to 85c sot23-5 5 packing method tape & reel top mark hbca fb g en out lx 1 2 3 4 5 ACT6305 uc sot23-5 all active-semi components are rohs compliant and wi th pb-free plating unless specified differently. the term ?pb-free? means semiconductor products that are in compliance wi th current rohs (restriction of hazardous substances) standards. pin configuration
ACT6305 rev0, 13-may-08 innovative power tm - 3 - www.active-semi.com copyright ? 2008 active-semi, inc. absolute maximum ratings c c : do not exceed these limits to prevent damage to the device. exposure to absolute maximum ra ting conditions for long periods m ay affect device reliability. electrical characteristics (v in = 1.5v, v out = 3.3v, t a = 25c, unless otherwise specified.) parameter value unit out, en to g -0.3 to 6 v fb, lx to g -0.3 to v out + 0.3 v continuous lx current internally limited a maximum power dissipation (derate 5mv/c above t a = 50c) 0.53 w junction to ambient thermal resistance ( ja ) 190 c/w operating junction temperature -40 to 150 c storage temperature -55 to 150 c lead temperature (soldering, 10 sec) 300 c parameter symbol test cond itions min typ max unit minimum operating input voltage v in 0.6 v startup voltage v in i load = 1ma 1 1.18 v output voltage v out fb = out; 60mv pp ripple 3.2 3.3 3.4 fb = g; 40mv pp ripple 4.85 5 5.15 output voltage range external feedback divider 2 5 v quiescent current at out i q v fb = 1.3v 17 34 a shutdown supply current i sd en = g 0.1 1 a startup to normal transition threshold 1.85 v fb feedback voltage v fb v out = 2v to 5v 1.15 1.180 1.21 v fb input current fb = 1.3v 50 na power switch current limit i lim 0.7 1 1.25 a power switch on resistance r onn i lx = 100ma 0.19 0.4 ? synchronous rectifier on resistance r onp i lx = -100ma 0.21 0.4 ? lx leakage current en = g, v lx = 0v or 3.3v 0.1 1 a maximum switch on-time t onmax 3.75 5 6.25 s minimum switch off-time t offmin 0.75 1 1.25 s en logic low threshold v il 0.4 v en logic high threshold v ih 0.6 v en input current 1 a v maximum operating input voltage v in 5 v
ACT6305 rev0, 13-may-08 innovative power tm - 4 - www.active-semi.com copyright ? 2008 active-semi, inc. typical performanc e characteristics (typical application circuit, l = 6.8 h, c1 = 22f ceramic, c2 = 22f ceramic, unless otherwise specified.) efficiency (%) efficiency vs. constant current ACT6305-002 constant current (ma) 0.1 1 10 100 1000 40 50 60 70 80 90 100 30 v in = 1.2v v in = 1.8v v in = 2.4v v out = 3.3v fb = out efficiency (%) efficiency vs. constant current ACT6305-003 constant current (ma) 0.1 1 10 100 1000 40 50 60 70 80 90 100 30 v in = 2.4v v out = 5v fb = g l = 4.7h c1 = 10f efficiency (%) efficiency vs. constant current ACT6305-004 constant current (ma) 0.1 1 10 100 1000 40 50 60 70 80 90 100 30 v in = 1.8v v out = 3.3v fb = out l = 4.7h c1 = 10f v in = 5v startup voltage (v) startup voltage vs. constant resistance load ACT6305-005 current load at 5v (ma) 0 150 200 1.00 1.50 2.00 0.5 100 startup voltage (v) startup voltage vs. constant resistance load ACT6305-006 current load at 3.3v (ma) 0 50 150 200 1.00 1.50 2.00 0.5 v out = 5v fb = g 100 efficiency (%) efficiency vs. output current ACT6305-001 output current (ma) 40 60 80 100 0.1 1.0 10 1000 30 v in = 3.5v v in = 1.2v v out = 5v fb = g 100 v in = 5v 50 70 90 v in = 2.4v v in = 3.5v v in = 2.4v v in = 1.2v v in = 1.2v 50 1.75 1.25 0.75 1.75 1.25 0.75 v out = 3.3v fb = out
ACT6305 rev0, 13-may-08 innovative power tm - 5 - www.active-semi.com copyright ? 2008 active-semi, inc. -20 typical performance ch aracteristics cont?d (typical application circuit, l = 6.8 h, c1 = 22f ceramic, c2 = 22f ceramic, unless otherwise specified.) quiescent supply current vs. temperature ACT6305-010 ACT6305-008 maximum on-time vs. temperature minimum off-time vs. temperature ACT6305-009 40 20 0 1.5 1.0 0.5 60 80 120 temperature (c) startup voltage (v) startup voltage vs. temperature ACT6305-007 100 -40 -20 40 20 0 60 80 120 temperature (c) 100 6.5 5.5 4.5 maximum on-time (s) -40 1.5 1.2 1.0 minimum off-time (s) 1.1 1.3 1.4 -20 40 20 0 60 80 120 temperature (c) 100 -40 25 10 0 quiescent supply current (a) 5 15 20 -20 40 20 0 60 80 120 temperature (c) 100 -40
ACT6305 rev0, 13-may-08 innovative power tm - 6 - www.active-semi.com copyright ? 2008 active-semi, inc. typical performance ch aracteristics cont?d (typical application circuit, l = 6.8 h, c1 = 22f ceramic, c2 = 22f ceramic, unless otherwise specified.) medium load operation for low esr c out ACT6305-012 ch2 ch1 ch1: v lx , 2.00v/div ch2: v out , 100mv/div time: 2.50s/div ch1: v lx , 2.00v/div ch2: v out , 100mv/div time: 100s/div ch2 ACT6305-011 light load operation for low esr c out ch1 v out = 5v v in = 1.2v i load = 5ma v out = 5v v in = 1.2v i load = 150ma ACT6305-013 ch2 ch1 medium load operation for low esr c out ch1: v lx , 2.00v/div ch2: v out , 100mv/div time: 2.50s/div v out = 5v v in = 2.4v i load = 300ma ACT6305-014 heavy load operation for low esr c out ch2 ch1 ch1: v lx , 2.00v/div ch2: v out , 50mv/div time: 2.50s/div v out = 5v v in = 3.6v i load = 500ma medium load operation for low esr c out ch2 ch1 ch2 ACT6305-015 light load operation for low esr c out ch1 ACT6305-016 ch1: v lx , 2.00v/div ch2: v out , 50mv/div time: 25.0s/div ch1: v lx , 2.00v/div ch2: v out , 100mv/div time: 2.50s/div v out = 3.3v v in = 1.2v i load = 50ma v out = 3.3v v in = 1.8v i load = 400ma
ACT6305 rev0, 13-may-08 innovative power tm - 7 - www.active-semi.com copyright ? 2008 active-semi, inc. functional description as seen in the functional block diagram , the ACT6305 comprises a reference, low input startup circuitry, feedback select, error comparator, control logic and timers, internal power mosfets and cur- rent comparators. main control loop the ACT6305 control archit ecture utilizes a series of one-shot and current sense circuits to regulate the output voltage with a very low quiescent supply current of just 17a. an on cycle begins when fb falls below the ACT6305?s internal reference volt- age. during an on cycle, the n-channel power switch is turned on to connect the lx node to ground, transferring energy from input supply to the inductor. the on cycle persists or the 1a current limit is reached. when either of these conditions occurs, the n-channel power switch turns off and the off cycle begins. during the off cycle, the energy stored in the inductor is released into the output capacitor and load through the synchronous rectifier. once the 1s minimum off time expires, another on cycle begins when the fb voltage drops below the reference voltage. light load operation under light load conditions, the ic automatically enters a power-saving mo de by extending the off time. this reduces switching losses and allows the ACT6305 to maintain high efficiency across a very wide load range. low voltage startup the ACT6305 uses proprietary start-up circuitry that allows it to achieve very low voltage startup down to 1v. the ACT6305 remains in low voltage startup mode until v out exceeds 1.85v. the ACT6305 can- not support its full rated load current when operat- ing in low-voltage startup mode. care should be taken to minimize load current during startup. shutdown in shutdown mode, all internal circuits including the power switch and the synchronous rectifier are dis- abled, reducing quiescent supply current to less than 1a. note that in shutdown mode, a dc path from the input supply to the output still exists due to the body diode of the sy nchronous rectifier. functional block diagram out lx g reference feedback select v ref v ref + driver error comparator low input start up 1s one -shot 5s one -shot set latch q reset current limit comparator en fb + ? + ? ?
ACT6305 rev0, 13-may-08 innovative power tm - 8 - www.active-semi.com copyright ? 2008 active-semi, inc. applications information output voltage selection the ACT6305 provides fixed output voltage options of 3.3v or 5v, or the output voltage may be ad- justed over a 2v to 5v range by connecting an external resistive voltage divider. when output volt- age is set by external resistive voltage divider, add a 47pf to 150pfcapacitor as feedforward capacitor (c ff ) as shown in figure 1. table 1: output voltage programming figure 1: output voltage setting output capacitor selection a minimum value of output capacitance is required to maintain loop stability and normal operation of the ic. the output capacitor value should be in the range of 22f to 100f. to obtain small output rip- ple, use a large capacitor with low esr. ceramic capacitors should be used for highest performance. if a tantalum capacitor is used, choose only low esr types and a smaller low esr capacitor of about 1f can be connected in parallel to filter high frequency noise. inductor selection for most applications, the inductor value should be in the range of 4.7h to 22h. smaller inductors provide faster load transient response and have a smaller physical size, but t hey also result in higher ripple current and reduce the maximum available output current. choose inductors with low series resistance to obtain the highest efficiency. board layout to reduce noise and increase efficiency, high cur- rent traces should be wide and direct, and an ex- tended ground plane should be used. switching current paths should be laid out as tightly as possi- ble, with the inductor and input and output capaci- tors located close to the ic in order to reduce elec- tromagnetic radiation. if an external resistor divider is used, place the re- sistors very close to the fb and g pins, and keep them away from the high switching current paths. fb = out v out = 3.3v fb = g v out = 5v fb connect to resistive divider v out = 1.18v (1 + r fb1 /r fb2 ) fb ACT6305 v out r fb1 r fb2 out c ff
ACT6305 rev0, 13-may-08 innovative power tm - 9 - www.active-semi.com copyright ? 2008 active-semi, inc. symbol dimension in millimeters dimension in inches min max min max a 1.050 1.250 0.041 0.049 a1 0.000 0.100 0.000 0.004 a2 1.050 1.150 0.041 0.045 b 0.300 0.400 0.012 0.016 c 0.100 0.200 0.004 0.008 d 2.820 3.020 0.111 0.119 e 1.500 1.700 0.059 0.067 e1 2.650 2.950 0.104 0.116 e 0.950 typ 0.037 typ e1 1.800 2.000 0.071 0.079 l 0.700 ref l1 0.300 0.600 0.012 0.024 0 8 0 8 0.028 ref package outline sot23-5 package outline and dimensions active-semi, inc. reserves the right to modify the circuitry or specifications without notice. user s should evaluate each product to make sure that it is suitable for their applicat ions. active-semi products are not intended or authorized for use as critical components in life-support dev ices or systems. active-semi, inc. does not assume any liability arising out of the use of any product or circuit described in this datasheet, nor does it convey any patent license. active-semi and its logo are trademarks of active-semi, in c. for more information on this and other products, contact sales@active-semi.com or visit http://www.active-semi.com. for other inquiries, please send to: 1270 oakmead parkway, suite 310, su nnyvale, california 94085-4044, usa d b e1 e e e1 a1 a2 a c ll1 0.2
|
