internal document do not copy introduction the aat1143 evaluation board demonstrates performance, as well as suggested size and placement of exter- nal components, for the aat1143 integrated buck regulator. the external components are selected for mini- mum size and optimum operation up to 400ma output current. resistors r1 and r2 set the output voltage. for improved transient response, a 100pf to 150pf capacitor can be used for c4, along with increasing the value of c1 to 10f. c3 is available for cases where additional external compensation is necessary; for most applications it is not used. refer to the aat1143 datasheet for more details about this product. layout as with all switching power supplies, the board layout for the aat1143 is critical (see figure 1). special care has been taken with the placement of external components. the input capacitor (c2) placement is critical. it must be placed immediately adjacent to the aat1143. as shown in figure 2, the output voltage feedback trace has been routed on the portion of the back side of the board which has a ground plane on the top side (see figure 3). the trace is also routed to avoid the lx node and associated noise. resistors r1 and r2 are placed as closely as possible to the aat1143 in order to minimize the length of the trace for the high impedance node associated with the out pin. this minimizes the potential for external noise associated with the power stage of the aat1143 and other circuitry coupling into the feedback of the aat1143. please refer to table 1 for aat1143 evaluation board specifications. figure 1: aat1143 evaluation board schematic for enhanced transient response version; c4 = 100pf; c1 = 10f. table 1: aat1143 evaluation board specifications. specification test conditions min typ max units input voltage 2.7 3.6 5.5 v output error voltage -3 +3 % output current 0 0.4 a l1 4.7 f c1 4.7 f c2 v out gnd v in 1 2 3 enable lx en 1 out 2 vin 3 lx 4 agnd 5 pgnd 6 pgnd 7 pgnd 8 aat1143 u1 gnd r1 59k r2 c3 c4 ev-106.2005.04.1.1 1 ev-106 aat1143eval 1mhz 0.4a buck converter
internal document do not copy figure 2: aat1143 evaluation figure 3: aat1143 evaluation board pcb top side. board pcb bottom side. test equipment 1. 6.0v 1.0a laboratory power supply: hp33401a or equivalent. 2. dc 0 to 0.4a electronic load, capable of operation down to 0.6v: keithley 2400 or equivalent. (when using the keithley 2400, set the meter to operate in voltage source mode and set the load current by varying the current compliance [maximum current] of the meter.) 3. dc voltmeter: hp34401a or equivalent. 4. oscilloscope: tektronix tds744a or equivalent. setup and test a: load and line regulation (see connection diagram in figure 4) 1. short (apply jumper to) pins 2 and 3 of the enable connector. 2. apply a dc power supply and dc voltmeter across input voltage terminals: v in (positive terminal) and gnd (negative terminal or return). 3. apply a dc load and dc voltmeter to output terminals v out and gnd. 4. vary the load from 0 to 0.4a and the input voltage from 2.7v to 5.5v while monitoring the output voltage. 5. the output voltage as measured at the output terminals of the evaluation boards should not vary by more than 1% of the nominal voltage. b: short-circuit and over-temperature protection 1. raise the input voltage to 5.5v. 2. apply a short from v out to gnd at the evaluation board terminals. 3. remove the short and verify that output returns to its initial value. c: enable input 1. remove the jumper from pins 2 and 3 of the enable connector and apply to pins 1 and 2. the output should decay to zero. 2. remove the short and replace the short from pins 2 to 3 of the enable connector. the output should recover to its initial value. 2 ev-106.2005.04.1.1 ev-106 aat1143eval 1mhz 0.4a buck converter
internal document do not copy figure 4: aat1143 connection diagram. table 2: aat1143 eval bill of materials. component part number description manufacturer u1 aat1143ijs-0.6-t1, 1mhz 0.4a buck converter analogictech aat1143ijs-1.5-t1 c2 grm319r60j476ke01 4.7f, 10v, x5r, 10%, 0805 murata grm319r60j476ke01 4.7f, 10v, x5r, 10%, 0805 c1 grm319r60j106ke01 10f, 6.3v, x5r, 10%, 0805 murata (optional for improved transient response 1 ) r1 chip resistor see table 3, 1%, 1/16w, 0402 vishay r2 chip resistor 59.0k ? , 1%, 1/16w, 0402 vishay l1 cdrh3d16-4r7 4.7h, 105m ? , 900ma, shielded cdrh3d16-10r 10h, 210m ? , 550ma, shielded (see table 3) sumida c4 chip capacitor 100pf, 25v, c0g, 10%, 0402 vishay (optional for improved transient response 1 ) c3 chip capacitor n/a vishay voltmeter 1.500v load 0-400ma 3.650v 0.147a power supply voltmeter 3.600v oscilliscope ev-106.2005.04.1.1 3 ev-106 aat1143eval 1mhz 0.4a buck converter 1. for improved transient response version, add c4 and increase c1 to 10f.
internal document do not copy output voltage for an adjustable output, set r2 to 59k ? and select r1 according to table 3. table 3: component selection for adjustable output voltage (r2 = 59.0k ? ? ). v o (v) r1 (k ? ? ) l1 (h) 0.6 0 4.7 0.8 19.6 4.7 1.0 39.2 4.7 1.5 88.7 4.7 1.6 97.6 4.7 1.7 110 4.7 1.8 118 4.7 2.5 187 10 ev-106 aat1143eval 1mhz 0.4a buck converter 4 ev-106.2005.04.1.1 advanced analogic technologies, inc. 830 e. arques avenue, sunnyvale, ca 94085 phone (408) 737-4600 fax (408) 737-4611 analogictech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an analogictech pr oduct. no circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. analogictech reserves the right to make changes to their products or specifications or to discontinue any product or service wi thout notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. all products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of l iability. analogictech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accorda nce with analogictech?s standard warranty. testing and other quality control techniques are utilized to the extent analogictech deems necessary to support this warranty. specific tes ting of all parameters of each device is not necessarily performed.
form#: for001 rev. d
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