ev-103 aat1152 eval 850khz 1a buck regulator introduction the aat1152 msop evaluation board demonstrates performance, along with the suggested size and place- ment of external components, for the aat1152 integrated buck regulator. the external components are select- ed for minimum size and optimum operation up to 1a output current. please refer to the aat1152 datasheet for more details about this product. layout as with all switching power supplies, board layout for the aat1152 is critical (see figure 1). special care has been taken with the placement of the external components. the input capacitor (c1) placement is critical and it must be located immediately adjacent to the aat1152. as shown in figure 2, the lx node trace has been routed under c1 in order to facilitate placement of c1 close to the ic. the output voltage feedback trace has been routed on the portion of backside of the board which has a ground plane on the top side (see figure 3). the trace is routed to avoid the lx node and associated noise. please refer to table 1 for aat1152 evalua- tion board specifications. figure 1: aat1152 evaluation board schematic. table 1: aat1152 evaluation board specification. specification test conditions min typ max units input voltage 2.7 3.6 5.5 v output error voltage 3 % output current 0 1.0 a 4.1 h l1 3x 22 f 6.3v x5 r c3-c5 10 f c1 100 r1 0.1 f c2 100k r2 v o + v in + v o - fb 1 sgnd 2 en 3 vcc 4 vp 5 lx 6 pok 7 pgnd 8 aat1152 u1 100k r5 r3 10k 1% r4 pok en ev-103.2005.07.1.1 1
figure 2. aat1152 evaluation board figure 3. aat1152 evaluation board pcb top side. pcb bottom side. test equipment 1. 6.0v 2.0a laboratory power supply: hp33401a or equivalent. 2. dc 0a to 1.0a load capable of operation down to 1.0v: keithley 2400 or equivalent. when using the keithley 2400, set the meter to 0v 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. apply a dc power supply and dc voltmeter across input voltage terminals: v in + (positive terminal) and gnd (negative terminal or return). 2. apply a dc load and dc voltmeter to output terminals: v o + and gnd. 3. vary the load from 0a to 1.0a and the input voltage from 2.7v to 5.5v while monitoring the output voltage. 4. the output voltage as measured at the output terminals of the evaluation board should not vary by more than 3% 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 o + to gnd at the evaluation board terminals. 3. remove the short and verify that output returns to its initial value. c: enable input 1. short the enable pin to gnd. the output should decay to zero and the power ok output should go low. 2. remove the short applied to the enable pin. the output should recover to its initial value and the power ok output should return to the input voltage. ev-103 aat1152 eval 850khz 1a buck regulator 2 ev-103.2005.07.1.1
figure 4: aat1152 connection diagram. table 2: aat1152 eval bill of materials. component part number description manufacturer u1 aat1152iks-1.0-t1 1.0v 1a buck converter analogictech u1 aat1152iks-1.8-t1 1.8v 1a buck converter analogictech u1 aat1152iks-2.5-t1 2.5v 1a buck converter analogictech u1 aat1152iks-3.3-t1 3.3v 1a buck converter analogictech c3, c4, c5 grm21br60j226ke19 22f, 6.3v, x5r, 10%, 0805 murata c1 grm319r60j106ke01 10f, 6.3v, x5r, 10%, 1206 murata c2 grm155r61a104ka01 0.1f, 25v, x5r, 10%, 0402 murata r1 chip resistor 100k ? , 5%, 1/16w; 0402 vishay r2 chip resistor 100k ? , 5%, 1/16w; 0402 vishay l1 cdrh5d18-4r1 4.1h, 57m ?, 1.95a shielded sumida aat1152ks-1.0-t1 table 3, 1%, 1/16w; 0402 vishay r3 chip resistor aat1152iks-1.8-t1 0 ? , 0402 vishay aat1152iks-2.5-t1 0 ? , 0402 vishay aat1152iks-3.3-t1 0 ? , 0402 vishay r4 chip resistor 10k ? , 1%, 1/16w; 0402 (required with vishay aat1152iks-1.0-t1 when output is >1.0v only) voltmeter 1.500v load 0-1a 3.650v 0.147a power supply voltmeter 3.600v ev-103 aat1152 eval 850khz 1a buck regulator ev-103.2005.07.1.1 3
output voltage for an adjustable output, set r4 to 10k ? and select r3 according to table 3 using the aat1152iks-1.0-t1. table 3: resistor selection for adjustable output voltage (r4 = 10k ? ? ). v o (v) r3 (k ? ? ) 1.0 0.00 (short) 1.1 1.00 1.2 2.00 1.25 2.55 1.3 3.01 1.4 4.02 1.5 4.99 1.6 6.04 1.7 6.98 1.8 8.06 1.85 8.45 1.9 9.09 2.0 10.0 2.1 11.0 2.2 12.1 2.3 13.0 2.4 14.0 2.5 15.0 3.3 23.2 ev-103 aat1152 eval 850khz 1a buck regulator 4 ev-103.2005.07.1.1 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.
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