EV-104 AAT1154EVAL 1MHz 3A Buck DC/DC Switch Mode Regulator Introduction The AAT1154 evaluation board demonstrates performance, along with the suggested size and placement of external components, for the AAT1154 integrated buck regulator. The external components are selected for minimum size and optimum operation up to 3.0A output current. Please refer to the AAT1154 datasheet for more details about this product. Component Summary Capacitor C4 is a high equivalent series resistance (ESR) tantalum for damping the high Q input network associated with the inductance of the leads feeding the input power to the evaluation board and the low ESR 10µF ceramic input capacitor (C1). R2 is a pull-up resistor to allow the enable pin to be used to enable and disable the IC by either shorting the enable pin to GND or leaving the pin open. Both R2 and C4 are for demonstration purposes only and are not necessary in the final solution. Resistors R3 and R4 are used with the 1V model to set the out voltage to any desired value from 1V to as high as 200mV below the minimum input voltage. They are not required for the fixed output voltage versions of the AAT1154. For fixed output voltage versions, R4 is omitted and R3 is replaced with a short. Layout As with all switching power supplies, the board layout for the AAT1154 is critical (see Figure 1). Special care has been taken with the placement of the external components. The input capacitor (C1) placement is critical; it must be placed immediately adjacent to the AAT1154. As can be seen 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 the back side 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 AAT1154 evaluation board specifications. VIN+ VO+ R1 100 U1 AAT1154 R3 C4 100µF 1 R2 100k 2 3 Enable 4 C1 10µF C3 0.1µF FB VP GND LX EN LX VCC VP 8 7 L1 1.5uH 6 5 CR1 B340LA R4 10.0k C2 120µF GND Figure 1: AAT1154 Evaluation Board Schematic. EV-104.2005.01.1.0 1 EV-104 AAT1154EVAL 1MHz 3A Buck DC/DC Switch Mode Regulator Specification Test Conditions Input Voltage Output Error Voltage Output Current Min Typ Max Units 2.7 3.6 ±3 5.5 V % A 0 3.0 Table 1: AAT1154 Evaluation Board Specifications. Figure 2: AAT1154 Evaluation Board PCB Top Side. Figure 3: AAT1154 Evaluation Board PCB Bottom Side. Test Equipment 1. 6.0V 10A laboratory power supply: HP33401A or equivalent. 2. DC 0A to 3.0A load capable of operation down to 1.0V: Keithley 2400 or equivalent. When using the Keithley 2400, set the meter to zero volts 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: VIN+ (positive terminal) and GND (negative terminal or return). 2. Apply a DC load and DC voltmeter to output terminals. VO+ and GND. 3. Vary the load from 0 to 3.0A 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 VO+ to GND at the evaluation board terminals. 3. Remove the short and verify that output returns to its initial value. 2 EV-104.2005.01.1.0 EV-104 AAT1154EVAL 1MHz 3A Buck DC/DC Switch Mode Regulator C: Enable Input and Power OK Output 1. Short the enable pin to GND. The output should decay to zero. 2. Remove the short applied to the enable pin. The output should recover to its initial value. 3.600V Power Supply 3.650V 0.147A Voltmeter 1.500V Load Voltmeter 0-3.0A Figure 4: AAT1154 Connection Diagram. Component U1 U1 U1 U1 CR1 C2 C4 C1 C3 R1 R2 L1 Part Number Description AAT1154IKS-1.0-T1 AAT1154IKS-1.8-T1 AAT1154IKS-2.5-T1 AAT1154IKS-3.3-T1 B340LA 594D127X96R6R3C2T 565D107X0016C GRM319R60J106KE01 GRM155R61A104KA01 Chip Resistor Chip Resistor CDRH6D28-1R5 1.0V, 1MHz, 3.0A Buck Converter 1.8V, 1MHz, 3.0A Buck Converter 2.5V, 1MHz, 3.0A Buck Converter 3.3V, 1MHz, 3.0A Buck Converter Low VF, 3A, 40V Schottky Diode 120µF, 6.3V, Tantalum 100µF, 16V, Tantalum 10µF, 6.3V, X5R, 10%, 1206 0.1µF, 25V, X5R, 10%, 0603 100kΩ, 5%, 1/10W, 0603 100kΩ, 5%, 1/10W, 0603 1.5µH Shielded Inductor AAT1154IKS-1.0-T1, Table 3, 1%, 1/10W, 0603 AAT1154IKS-1.8-T1 thru AAT1154IKS-3.3 -T1; 0Ω, 0603 AAT1154IKS-1.0-T1 (for output greater than 1.0V); 10kΩ, 1%, 1/10W; 0603 AAT1154IKS-1.8-T1 thru AAT1154IKS-3.3 -T1 R3 Chip Resistor R4 Chip Resistor Manufacturer AnalogicTech AnalogicTech AnalogicTech AnalogicTech Diodes Inc. Vishay Vishay MuRata MuRata Vishay Vishay Sumida Vishay Vishay Vishay n/a Table 2: AAT1154 EVAL Bill of Materials. EV-104.2005.01.1.0 3 EV-104 AAT1154EVAL 1MHz 3A Buck DC/DC Switch Mode Regulator Output Voltage For an adjustable output, set R4 to 10kΩ and select R3 according to Table 3 using the AAT1154IKS-1.0-T1. VO (V) Ω) R3 (kΩ 1.0 1.1 1.2 1.25 1.3 1.4 1.5 1.6 1.7 1.8 1.85 1.9 2.0 2.1 2.2 2.3 2.4 2.5 3.3 0.00 (short) 1.00 2.00 2.55 3.01 4.02 4.99 6.04 6.98 8.06 8.45 9.09 10.0 11.0 12.1 13.0 14.0 15.0 23.2 Ω). Table 3: Resistor Selection for Adjustable Output Voltage (R4=10.0kΩ AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. 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 without 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 liability. AnalogicTech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with AnalogicTech’s standard warranty. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed. Advanced Analogic Technologies, Inc. 830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737-4600 Fax (408) 737-4611 4 EV-104.2005.01.1.0