QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 734 DUAL SYNCHRONOUS, 800MA, 2.25 MHZ STEP-DOWN DC/DC REGULATOR LTC3407-2 DESCRIPTION Demonstration circuit 734 is a Dual Synchronous, 800mA, 2.25MHz Step-Down DC/DC Regulator featuring the LTC 3407-2. The DC734 has an input voltage range of 2.5V to 5.5V, and either output is capable of delivering up to 800mA of output current. In Burst Mode operation, the LTC3407-2 requires only 40uA of quiescent current, and the DC734 provides higher efficiency at light load currents. In Pulse Skip mode, the DC734 provides lower output ripple voltage at light load currents. In either mode, the DC734 can provide up to 96% efficiency on either channel and consumes less than 1uA in shutdown. The LTC3407-2 comes in a small 10-Pin DFN package, which has an exposed pad on the bottom-side of the IC for better thermal performance. These features, plus the nominal operating frequency of 2.25MHz (allowing the exclusive use of low profile surface mount components), make the DC734 demo board an ideal circuit for use in battery-powered, hand-held applications. Design files for this circuit board are available. Call the LTC factory. LTC is a trademark of Linear Technology Corporation Table 1. Performance Summary (TA = 25°C) PARAMETER Minimum Input Voltage CONDITION Maximum Input Voltage VALUE 2.5V 5.5V 1.2V ±2% Output Voltage VOUT1 VIN = 2.5V to 5.5V, IOUT1 = 0A to 800mA 1.5V ±2% 1.8V ±2% Typical Output Ripple VOUT1 VIN = 5V, IOUT1 = 800mA (20MHz BW) 20mVP–P Line ±1% Load ±1% Output Voltage VOUT2 VIN = 2.5V to 5.5V, IOUT2 = 0A to 800mA 2.5V ±2% Typical Output Ripple VOUT2 VIN = 5V, IOUT2 = 800mA (20MHz BW) 20mVP–P Line ±1% Load ±1% Output Regulation Output Regulation Nominal Switching Frequency 2.25MHz 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 734 DUAL SYNCHRONOUS, 800MA, 2.25 MHZ STEP-DOWN DC/DC REGULATOR QUICK START PROCEDURE Demonstration circuit 734 is easy to set up to evaluate the performance of the LTC3407-2. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below. Note: When measuring the input or output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. Measure the input or output voltage ripple by touching the probe tip directly across the Vin or Vout and GND terminals. See Figure 2. for proper scope probe technique. Note: Capacitor C5 is an optional part. It was inserted on the DC734 to dampen the (possible) ringing voltage due to the use of long input leads. On a normal, typical PCB, with short traces, the capacitor is not needed. 1. 2. 3. Connect the input power supply to the Vin and GND terminals on the left-side of the board. Do not hot-plug Vin or increase Vin over the rated maximum supply voltage of 5.5V, or the part may be damaged. Connect the loads between the Vout and GND terminals on the right-side of the board. Refer to Figure 1 for the proper measurement equipment setup. Before proceeding to operation, insert jumpers JP1 and JP2 into the OFF positions, jumper JP3 into the Vout1 voltage position of choice (1.2V, 1.5V, and 1.8V), and jumper JP4 into the desired mode of operation: Pulse Skip or Burst Mode. Apply 3.3V at Vin. Measure both Vouts; they should read 0V. If desired, one can measure the shutdown supply current at this point. The supply current will be approximately 33uA in shutdown, with roughly 32uA due to the optional 100kΩ pullup resistor of the Power-On Reset (POR) feature. This resistor can be removed, and the actual shutdown supply current (of approx. 1uA) can be measured, if the POR feature is not required. 4. Turn on Vout1 and Vout2 by changing jumpers JP1 and JP2 from the OFF position(s) to the ON position(s). Vary the input voltage from 2.5V to 5.5V and adjust each load current from 0 to 800mA. Both output voltages should be regulating. 5. Set the load current of both outputs between 200mA and 800mA, and measure both output ripple voltages; they should measure less than 20 mVAC each. Also, observe the voltage waveform at the switch node (pin 3) of each regulator. The switching frequencies should be between 1.8MHz and 2.7MHz (T = 0.555 us and 0.37 us), and each switch node waveform should be rectangular in shape. 6. To change the mode of operation, change jumpers JP1 and JP2 from the ON position(s) to the OFF position(s). Then change jumper JP4 to the alternative position. Re-insert jumpers JP1 and JP2 into the ON position(s). Observe the voltage waveform at both switch nodes. When finished, insert jumpers JP1 and JP2 OFF position(s) and disconnect the power. to the If more efficiency is desired from the Demo Circuit, replace the stock inductor, a Taiyo Yuden part # LQLBC2518M2R2M, with a Murata inductor, # LQH32CN2R2M11. Due to its large size, the Murata inductor has lower DCR than the Taiyo Yuden inductor, thus has less power dissipation. 2 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 734 DUAL SYNCHRONOUS, 800MA, 2.25 MHZ STEP-DOWN DC/DC REGULATOR Figure 1. Proper Measurement Equipment Setup Figure 2. Scope Probe Placement for Measuring Input or Output Ripple 3 5 4 3 2 1 * Capacitor C5 is an optional part. It was inserted on the DC734 to dampen the (possible) ringing voltage due to the use of long input leads. On a normal, typical PCB, with short traces, the capacitor is not needed. Vin Vin 2.5V-5.5V JP1 CH.1 On 2 Off Gnd On 2 R1 4.7M 5% U1 LTC3407-2EDD R2 100K R3 4.7M 5% Off VIN 1 E5 JP2 CH.2 1 Cin 10uF 6.3V 3 D C5* + 47uF 10V (Opt.) 3 E1 3 D Vout1 1.2V/1.5V/1.8V @ 800mA R4 604K RUN2 9 R5 604K R8 402K SW2 1 FBK1 11 GND R9 301K 5 2 4 6 + + + Vin 1 3 5 7 C2 22pF FBK2 C Vout2 2.5V @ 800mA R6 887K Cout2 10uF 6.3V C4 (Opt.) 10 E3 Gnd R7 280K E6 R10 4.7M 5% B 2 JP3 Vout1 E7 L2 2.2uH C1 22pF + + + B POR MODE/SYNC Cout1 10uF 6.3V 1.2V 1.5V 1.8V E4 SW1 L1 2.2uH C3 (Opt.) Gnd 4 POR 8 6 E2 RUN1 GND C 2 3 JP4 1 Burst Pulse Mode Skip LTC CONFIDENTIAL - FOR CUSTOMER USE ONLY Customer Notice A 5 4 LINEAR TECHNOLOGY CORPORATION 1630 McCARTHY BLVD. MILPITAS, CA. 95035 408-432-1900 408-434-0507 FAX Linear Technology Has Made A Best Effort To Design A Circuit That Meets Customer-Supplied Specifications; However, It Remains The Customer's Responsibility To Verify Proper And Reliable Operation In The Actual Application. Component Substitution And Printed Circuit Board Layout May Significantly Affect Circuit Performance Or Reliability. Contact Linear Technology Applications Engineering For Assistance. Size Document Number This Circuit Is Proprietary To Linear Technology And Supplied For Use With Linear Technology Parts. Date: Wednesday, June 23, 2004 3 Title A Dual Synchronous Step-Down DC/DC Converter Rev Demo Circuit 734A LTC3407-2EDD 2 Sheet 1 1 of 1 Item Qty 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 3 2 0 1 7 3 1 4 2 3 1 2 1 1 1 1 1 Reference COUT1,COUT2,CIN C2,C1 C3,C4 (Optional) C5 E1,E2,E3,E4,E5,E6,E7 JP1,JP2,JP4 JP3 JP1,JP2,JP3,JP4 L1,L2 R1,R3,R10 R2 R4,R5 R6 R7 R8 R9 U1 Description CAP, X5R 10uF 6.3V 20% 0805 CAP, NPO 22pF 50V 10% 0402 CAP, 0805 CAP, TANT 47uF 10V 20% 6032 TURRETS HEADER, 3PIN 2mm HEADER, 3X2 2mm SHUNT, INDUCTOR, 2.2uH RES, 4.7M OHMS 5% 1/16W 0402 RES, 100K OHMS 1% 1/16W 0402 RES, 604K OHMS 1% 1/16W 0402 RES, 887K OHMS 1% 1/16W 0402 RES, 280K OHMS 1% 1/16W 0402 RES, 402K OHMS 1% 1/16W 0402 RES, 301K OHMS 1% 1/16W 0402 IC, LTC3407-2EDD Part Number TAIYO YUDEN JMK212BJ106MG AVX 04025A220KAT TBD AVX TAJW476M010R MILL-MAX 2501-2 COMM CON 2802S-03-G1 COMM CON 2202S-06G1 COMM CON, CCIJ2MM-138G SUMIDA, CDRH2D18/LD2R2NC AAC CR05-475JM AAC CR05-1003FM AAC CR05-6043FM AAC CR05-8873FM AAC CR05-2803FM AAC CR05-4023FM AAC CR05-3013FM LINEAR TECH. LTC3407-2EDD