DEMO MANUAL DC1864A LTC3621-2 17V, 1A Monolithic Synchronous Step-Down Regulator DESCRIPTION Demonstration circuit 1864A is a step-down converter, capable of delivering up to 1A of output current from a minimum input voltage of 2.7V. The DC1864A uses the power-saving LTC®3621-2 2.25MHz monolithic synchronous buck regulator that comes in a tiny 2mm × 3mm 6-lead DFN package. The LTC3621-2 IC quiescent currents can be as low as 3.5µA in normal operation, and less than 0.1µA in shutdown. The output voltage range of the DC1864A is from as low as 0.6V, the reference voltage of the LTC3621‑2, to as high as the maximum input voltage, 17V. The DC1864A can operate in three distinct operating PERFORMANCE SUMMARY PARAMETER Input Voltage Range Output Voltage Range Run/Shutdown modes: Burst Mode® for highest efficiency at low output currents, forced continuous mode for lowest output ripple voltage, and pulse-skipping mode for the best compromise operation between the two other modes, by setting the MODE pin to INTVCC (3.6V), INTVCC/2, or ground respectively. All these features make the DC1864A an ideal circuit for use in any high efficient, low power application. Design files for this circuit board are available at http://www.linear.com/demo L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Specifications are at TA = 25°C CONDITIONS Output Voltage Regulation Typical Output Ripple Voltage Nominal Switching Frequency Operation Modes Burst Mode-to-CCM Operation INTVCC RUN Pin = GND RUN Pin = VIN VIN = 2.7V to 17V, IOUT = 0A to 1A VIN = 2.7V to 17V, IOUT = 0A to 1A VIN = 2.7V to 17V, IOUT = 0A to 1A VIN = 3.5V to 17V, IOUT = 0A to 1A VIN = 5.2V to 17V, IOUT = 0A to 1A VIN = 12V, VOUT = 5V, IOUT = 1A (20MHz BW) MODE Pin = INTVCC MODE Pin = GND MODE Pin = INTVCC/2 VIN = 12V, VOUT = 1.2V VALUE 2.7V to 17V 0.6V to VIN Shutdown Operating 1.2V ±3% Typ. (1.164V to 1.236V) 1.8V ±3% Typ. (1.746V to 1.854V) 2.5V ±3% Typ. (2.425V to 2.575V) 3.3V ±3% Typ. (3.201V to 3.399V) 5V ±3% Typ. (4.85V to 5.15V) < 20mVP-P 2.25MHz ±8% Burst Mode Operation Pulse-Skipping Forced Continuous IOUT < 500mA 3.6V ±8.33% (3.3V to 3.9V) Table 1. Jumper Description JUMPER FUNCTION/RANGE SETTING JP1 Run: ON – OFF. ON JP2 Mode: Burst Mode Operation (BM) or Pulse-Skipping Mode (PS) BM JP3 Output Voltage Setting. 1.2V dc1864af 1 DEMO MANUAL DC1864A QUICK START PROCEDURE Demonstration circuit 1864 is easy to set up to evaluate the performance of the LTC3621-2. For proper measurement equipment configuration, set up the circuit according to the diagram in Figure 1. Before proceeding to test, check that the shunts are inserted into the correct locations: 1.2V position of the output voltage header JP3, into the BM (Burst Mode operation) position of MODE header JP2, and into the ON position of RUN header JP1. 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 measurement technique. With the DC1864 set up according to the proper measurement configuration and equipment in Figure 1, apply 5V at VIN (Do not hot-plug VIN or increase VIN over the rated maximum supply voltage of 17V, or the part may be damaged.). Measure VOUT; it should read 1.2V. (If desired, the quiescent current of the circuit can be monitored now by swapping the shunt in header JP1 into the OFF position.) The output voltage should be regulating. Draw 500mA out of the output and measure VOUT — it should measure 1.2V ±2% (1.176V to 1.224V). Verify the switching frequency is between 1.8MHz and 2.6MHz (t = 55ns and 38ns), and that the switch node waveform is rectangular in shape. Set the input voltage to 12V and the output current to than 100mA. Observe the Burst Mode operation at the switch node (the pad of the inductor opposite from the output), and measure the output ripple voltage. It should measure less than 100mV. Change the shunt position on the MODE header from BM to PS (pulse-skipping mode) and observe the voltage waveform at the switch pins. To achieve forced continuous operation, insert two 100k resistors at the pads for R1 and R2. These resistors develop a voltage of INTVCC/2 at the MODE pin, which is the voltage setting for forced continuous operation. Insert the JP1 shunt into the OFF position and move the shunt in the 1.2V output JP3 header into any of the remaining output voltage option headers: 1.8V (JP4), 2.5V (JP5), 3.3V (JP6) or 5V (JP7). Just as in the 1.2V VOUT test, the output voltage should read VOUT ±2% tolerance under static line and load conditions and ±1% tolerance under dynamic line and load conditions (±3% total). Also, the circuit switch operation in Burst or pulse-skipping mode operation will remain the same. There is an extra output voltage header, JP8, to allow the user to easily set the output to their desired value When finished, turn off the circuit by inserting the shunt in header JP1 into the OFF position. Vary the input voltage from 2.7V to 17V and the load current from 0 to 1A. VOUT should regulate around 1.2V ±3% (1.164V to 1.236V). Measure the output ripple voltage; it should measure less than 20mV AC. dc1864af 2 DEMO MANUAL DC1864A QUICK START PROCEDURE Figure 1. Proper Equipment Measurement Setup Figure 2. Measuring Input or Output Ripple dc1864af 3 DEMO MANUAL DC1864A QUICK START PROCEDURE OUTPUT VOLTAGE 50mV/DIV AC OUTPUT CURRENT 500mA/DIV VIN = 12V, VOUT = 1.2V 500mA LOAD STEP (500mA TO 1A) PULSE-SKIPPING MODE fSW = 1MHz Figure 3. Load Step Response OUTPUT VOLTAGE 50mV/DIV AC OUTPUT CURRENT 500mA/DIV VIN = 12V, VOUT = 2.5V 500mA LOAD STEP (500mA TO 1A) PULSE-SKIPPING MODE fSW = 1MHz Figure 4. Load Step Response OUTPUT VOLTAGE 50mV/DIV AC OUTPUT CURRENT 500mA/DIV VIN = 12V, VOUT = 3.3V 500mA LOAD STEP (500mA TO 1A) PULSE-SKIPPING MODE fSW = 1MHz Figure 5. Load Step Response dc1864af 4 DEMO MANUAL DC1864A QUICK START PROCEDURE OUTPUT VOLTAGE 100mV/DIV AC OUTPUT CURRENT 500mA/DIV VIN = 12V, VOUT = 5V 500mA LOAD STEP (500mA TO 1A) PULSE-SKIPPING MODE fSW = 1MHz Figure 6. Load Step Response 90 85 VIN = 12V, Burst Mode OPERATION fSW = 2.25MHz L = 2.2µH, Coilcraft XFL-3012 EFFICIENCY (%) 80 75 70 VO = 5V VO = 3.3V VO = 2.5V VO = 1.8V VO = 1.2V 65 60 55 0.0001 0.001 0.01 0.1 1 LOAD CURRENT (A) Figure 7. Circuit Efficiency dc1864af 5 DEMO MANUAL DC1864A PARTS LIST ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Required Circuit Components 1 1 CFF CAP., X7R, 22pF, 50V, 0402 AVX 04025A220KAT 2 1 C1 CAP., X5R, 10µF, 25V, 10%, 1206 AVX 12063D106KAT 3 2 C2, C3 CAP., X5R, 22µF, 25V, 10%, 1206 AVX 12063D226KAT 4 1 C4 CAP., X5R, 1µF, 6.3V,20%, 0402 TDK, C1005X5R0J105M 5 1 L1 IND, FIXED INDUCTOR, 2.2µH COILCRAFT., XFL3012-222MEB 6 2 R3, RSET RES., CHIP, 619k, 1%, 0402 VISHAY CRCW0402619KFKED 7 1 U1 LTC3621EDCB-2, 6-LEAD DFN PACKAGE LINEAR TECH., LTC3621EDCB-2#PBF SANYO, 20TQC8R2M Additional Demo Board Circuit Components 1 1 C1A CAP., X5R, 8.2µF 20V, SIZE B2, 3528-7343 2 0 R1, R2 OPT RES., CHIP, 0402 3 1 R4 RES., CHIP, 309k, 1%, 0402 VISHAY CRCW0402309KFKED 4 1 R5 RES., CHIP, 196k, 1%, 0402 VISHAY CRCW0402196KFKED 5 1 R6 RES., CHIP, 137k, 1%, 0402 VISHAY CRCW0402137KFKED VISHAY CRCW040284K5FKED 6 1 R7 RES., CHIP, 84.5k, 1%, 0402 7 0 R8 OPT RES., CHIP, 0402 Hardware 1 8 E1-E8 TESTPOINT, TURRET, 0.095" MILL-MAX, 2501-2-00-80-00-00-07-0 2 2 JP1, JP2 2MM SINGLE ROW HEADER, 3-PIN SULLINS, NRPN031PAEN-RC 3 6 JP3-JP8 2MM SINGLE ROW HEADER, 2-PIN SULLINS, NRPN021PAEN-RC 4 3 JP1-JP3 SHUNT, SAMTEC, 2SN-BK-G dc1864af 6 Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. A B C D C1A 8.2uF 25V + BM (Burst Mode) E7 E1 SYNC GND 5 E5 E3 PS (Pulse-Skip) MODE/SYNC (Forced Continuous) INTVCC VIN 2.7V - 17V VIN 1 3 JP2 2 OFF ON R2 100k OPT R1 100k OPT C1 10uF 1 3 5 C4 1uF 4 RUN 2 JP1 4 6 5 3 2 4 1 3 L1 2.5V JP5 R5 196k Rset 619k 1.8V JP4 R4 309k 1.2V JP3 R3 619k 2.2uH 7 GND FB SW MODE/SYNC INTVCC RUN VIN LTC3621EDCB-2 U1 3 5.0V JP7 R7 84.5k C2 22uF TECHNOLOGY E6 E4 C3 22uF E2 GND GND 1A VOUT 2 1 USER SELECT JP8 R8 OPT CFF 22pF VOUT 1 17V VIN SYNCHRONOUS STEP-DOWN REGULATOR 3.3V JP6 R6 137k 2 A B C D DEMO MANUAL DC1864A SCHEMATIC DIAGRAM dc1864af 7 DEMO MANUAL DC1864A DEMONSTRATION BOARD IMPORTANT NOTICE Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions: This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations. If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES. The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or agency certified (FCC, UL, CE, etc.). No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind. LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive. Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and observe good laboratory practice standards. Common sense is encouraged. This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application engineer. Mailing Address: Linear Technology 1630 McCarthy Blvd. Milpitas, CA 95035 Copyright © 2004, Linear Technology Corporation dc1864af 8 Linear Technology Corporation LT 1213 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2013