www.acutechnology.com AQ112 AQ112 ultra-low dropout 1a voltage regulator product specification revision 1.6 september 13, 2006 applications ? graphic cards ? pc motherboards ? switching power supply post-regulation ? telecom equipment ? dvd video player general description the AQ112 is an ultra-low dropout three terminal voltage regulator, offered in popular fixed options or an adjustable version that can set a precise voltage from 1.22v to 12v with two external resistors. it drops into the footprint of the popular lm1117 sot-223 and provides a true 4 th pin separated from the output tab which allows a separate bias connection from the pass transistor in order to achieve enable and ultra low dropout from v in to v out . the enable pin provides a remote turn-off for low power consumption. it draws virtually zero current in shutdown mode and implements sequential, ratiometric, or simultaneous sequencing schemes. to assure accuracy within 1%, the heart of the AQ112 is a self-correcting acuref ? bandgap reference. on-chip current limit and thermal shutdown with hysteresis protects against any combination of overload and ambient temperature that might cause the junction temperature to exceed safe limits. features ? ultra low dropout (400mv at 1a) ? enable pin implements sequencing ? vout tolerance less than 1.5% over temperature ? stable with low cost 1uf capacitor ? thermal protection with hysteresis ? short circuit protection ? adjustable output ? the AQ112 is featured in the new sot223 4-lead tetrapack tm package. ? rohs compliant available typical application
acutechnology semiconductor inc. AQ112 www.acutechnology.com 2 rev. 1.6 september 13, 2006 pin configuration pin descriptions pin name function v in + unregulated input voltage, collector of pass transistor e nable active high, e nable > (0.95v + v out ), chip bias circuit supply off low, e nable < 0.25v ground/adjust ground or adjust pin (c onnect to resistive feed back divider) v out regulated output functional block diagram
acutechnology semiconductor inc. AQ112 www.acutechnology.com 3 rev. 1.6 september 13, 2006 ordering information device operating tj %tol pkg type v out wrap ordering number AQ112 0c ? 125c ? 1.0 sot-223-4 1.8v t&r AQ112cy-s4-18-tr AQ112 0c ? 125c ? 1.0 sot-223-4 1.8v t&r AQ112cy-s4-18-trl AQ112 0c ? 125c ? 1.0 sot-223-4 2.5v t&r AQ112cy-s4-25-tr AQ112 0c ? 125c ? 1.0 sot-223-4 2.5v t&r AQ112cy-s4-25-trl AQ112 0c ? 125c ? 1.0 sot-223-4 3.3v t&r AQ112cy-s4-33-tr AQ112 0c ? 125c ? 1.0 sot-223-4 3.3v t&r AQ112cy-s4-33-trl AQ112 0c ? 125c ? 1.0 sot-223-4 adj t&r AQ112cy-s4-aj-tr AQ112 0c ? 125c ? 1.0 sot-223-4 adj t&r AQ112cy-s4-aj-trl note: the trl parts are lead free and rohs compliant. absolute maximum ratings stress greater than those listed under ?absolute maximum ratings? may cause permanent damage to the device. these stress ratings only, and functional operation of the devic e at these or any conditions beyond those indicated under recommended operating conditions is not implied. exposure to ?absolute maximum rating? for extended periods may affect device reliab ility. use of standard esd handling precautions is required. parameter value units maximum v in 18 volts maximum v enable 18 volts power dissipation (internally limited) maximum junction temperature 150 c operating junction temperature range 0 to 125 c storage temperature range -65 to 150 c lead temperature (soldering, 4sec.) sot- 223 package 300 c thermal management thermal resistance (junction to tab) typical value units sot-223 15 c/w thermal resistance (junction to ambient) typical value units sot-223 (tab soldered to 1 in 2 1 oz. copper pcb) 46 c/w
acutechnology semiconductor inc. AQ112 www.acutechnology.com 4 rev. 1.6 september 13, 2006 electrical specifications electrical characteristics are guaranteed over the full temperature range 0oc acutechnology semiconductor inc. AQ112 www.acutechnology.com 5 rev. 1.6 september 13, 2006 typical response curves
acutechnology semiconductor inc. AQ112 www.acutechnology.com 6 rev. 1.6 september 13, 2006 application notes 1. typical application notes: 1. output voltage is 1.22v * (r2 +r1)/r1 2. input and output capacitors should be located close to the device. 3. the AQ112 will remain stable with c1 and c2 as low as 1.0 f. overall transient performance is improved wi th increased capacitance and the addition of c3. 4. the output is fully enabled when e nable is 950 mv above the expected v out . en may be driven by either a digital or analog signal to control either turn-on time or to give full control of risetime. 5. enable, tied to any separate source >0.95v + v out , will insure ultra-low drop out voltage (400mv@ 1a) from v in to v out . or, enable, tied to vin will support a low drop out voltage (0.95v). 2. stability an enable capacitor is recomm ended. a 1.0 f capacitor on v in is a suitable input bypass for almost all applications. a lar ger capacitor is also suitable. in the adjustable version the ?adjust? term inal can be bypassed to ground with a bypass capacitor (c adj ) to improve ripple rejection. this by pass capacitor prevents ripple from being amplified as the output voltage is increased. at any ripple frequency, the impedance of the c adj should be less than r1 (being r1 the resist or between the output and the adjust pin) to prevent the ripple from being amplified: z = 1/(2 *f ripple * c adj ) < r1 r1 is normally in the range of 1k ? . the output capacitor is critical in maintaining regular stability. the aq1541 is stable with an output capacitor greater than 1.0 f. of cour se any increase of the output capacitor will merely improve the loop stability and the load transient response. in the case of the adjustable regulator, when the c adj is used, a larger output capacitance may be required. the capacitor c3 may also be necessary if large ripple is present on the v in line. tantalum capacitors exhibit the best stability over a wide range of loads and are recommended.
acutechnology semiconductor inc. AQ112 www.acutechnology.com 7 rev. 1.6 september 13, 2006 3. output voltage the AQ112 adjustable version develops a 1. 22v reference voltage between the output and the adjust pin terminal. this voltage is applied across the resistor r1 to generate a constant current (i1). the current from the adjust termi nal could introduce error to the output, but since it is very small (< 20a) compared with the current i1 and very constant with line and load changes, the error can be ignored. the constant current i1 then flows through resistor r2 and sets the output voltage to the desired level. for fixed voltages the resistor r1 and r2 are integrated inside the devices. the AQ112 regulates the voltage that appear s between its output and ground pins or between its output and adjust pins. in some case s, line resistances can introduce errors to the voltage across the load. to obtain the bes t load regulation a few precautions are needed. for example it is important to minimize the li ne resistances to the load, so the load itself should be tied directly to the output terminal on the positive side and directly to the ground terminal on the negative side. when the adjustable regulator is used, the best performance is obtained with the positive side of the resistor r1 tied directly to the output terminal of the regulator rather than near the load. this will eliminate line drops from appearing effectively in series with the reference and degrading regulation. in addition the ground side of the resistor r2 can be returned near the ground of the load to provide remote gr ound sensing and improve load regulation. a capacitor (470pf) between the adj pin and system ground will enhance stability. 4. enable/sequencing the AQ112 provides an enable function. the en pin has to be at least 950 mv higher than the output voltage for the device to be fully tur ned on. when the voltage of the en pin is low the device is in shutdown mode and it w ill not draw any current from the v in terminal. out 0 enable fig.2 enable 0-5v, output follows to 3.3v out (1v/div vertical, 200us/div horizontal) in addition the enable function includes a s equencing feature, because when the enable pin ramps in voltage the output voltage follows (it will be around 900 mv less than the enable voltage until it reaches the regulation vo ltage) as shown in fig. 2 above.
acutechnology semiconductor inc. AQ112 www.acutechnology.com 8 rev. 1.6 september 13, 2006 in applications where multiple regulated supply rails are required, it is often required that the relationship between the various supply voltages be controlled during start-up and shutdown. to this end, the AQ112 allows for an anal og control of the output voltage via the enable pin. this allows for sequential, ratio-me tric and simultaneous sequencing schemes. 4. protection diodes unlike older regulators, the AQ112 family does not need any protection diodes between the adjustment pin and output or from the output to t he input to prevent over-stressing the die. internal resistors are limiting the internal cu rrent paths on the adjustment pin. therefore, even with capacitors on the adjustment pin, no protection diode is needed to ensure device safety under short circuit conditions. exter nal diodes between the input and output are not usually needed. only if high value output c apacitors are used (> 1000uf) and the input is instantaneously shorted to ground, can damage occur. 5. thermal considerations when an integrated circuit operates with an apprec iable current, its junction temperature is elevated. it is important to quantify its ther mal limits in order to achieve acceptable performance and reliability. this limit is determined by summing the individual parts consisting of a series of temperature rises from the semiconductor junction to the operating environment. the heat generated at the device j unction flows through the die to the die attach pad, through the lead frame to the surrounding case material, to the printed circuit board, and eventually to the ambient environment. the AQ112 regulators have internal thermal s hutdown to protect the device from over- heating. under all possible operating conditi ons, the junction temperature of the AQ112 must be lower than 125c. a heatsink may be required depending on the maximum power dissipation and maximum ambient te mperature of the application. to determine if a heatsink is needed, t he power dissipated by the regulator, p d , must be calculated: p d = (v c -v out ) i l where the i l is the load current. the next parameter which must be calculated is the maximum allowable temperature rise, t(max): t(max)=t j (max)-t a (max) where t j (max) is the maximum allowable junction temperature (125c), and t a (max) is the maximum ambient temperature which will be encountered in the application. using the calculated values for t(max) and p d , the maximum allowable value for the junction to ambient thermal resistance ( ja ) can be calculated: ja =t(max)/ p d if the maximum allowable value for ja is found to be greater than the junction to ambient thermal resistance for the package used, no heatsink is needed since the package alone will dissipate enough heat to satisfy these requirements.
acutechnology semiconductor inc. AQ112 www.acutechnology.com 9 rev. 1.6 september 13, 2006 7. ultra low dropout operation the AQ112 allows for ultra low dropout operation by connecting the pin enable to >0.95v + vout. this results in a dropout of 100 mv at 150 ma of load current, between vin and v out . this feature is important when the supply vo ltage is dropping near the output regulated voltage. furthermore if the voltage dropout is low, the in ternal power dissipation is also reduced and the thermal requirements of t he device are less stringent.
acutechnology semiconductor inc. AQ112 www.acutechnology.com 10 rev. 1.6 september 13, 2006 package dimensions sot223-4 tetrapack tm contact information acutechnology semiconductor inc. tel: (408) 259-2300 3487 mckee rd. suite 52 fax: (408) 259-9160 san jose ca , usa 95127 website: www.acutec hnology.com disclaimer the information furnished by acutechnology in this data s heet is believed to be accurate and reliable. however, acutechnology assumes no responsibility for it s use. acutechnology reserves the right to change circuitry and specifications at any time without notific ation to the customer. life support policy acutechnology products are not designed or authorized for use as components in life support devices or systems where malfunction of a product can reasonably be ex pected to result in personal injury. life support devices or systems are devices or systems that (a) are intended fo r surgical implant into the body or (b) support or sustain life, and whose failure t o perform can be reasonably expected to result in a significant injury to the user. tetrapack ? and acuref ? are trademarks of acutechnology semiconductor inc
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