DEMO MANUAL DC1768A DESCRIPTION LTC3626EUDC 20V, 2.5A Synchronous Monolithic Step-Down Regulator with Current and Temperature Monitoring Demonstration circuit 1768A is a step-down converter, using the LTC3626 monolithic synchronous buck regulator, which has current and temperature monitoring capabilities. The 1768A has an input voltage range of 3.6V to 20V, and is capable of delivering up to 2.5A of output current. The output voltage of the 1768A can be set as low as 0.6V, the reference voltage of the LTC3626. At light load currents, the 1768A is capable of operating in Burst Mode™, which makes for greater efficiency, and during shutdown, it consumes less than 2μA of quiescent current. In continuous mode operation, the 1768A is a high efficiency circuit over 90%. The 1768A can also track another voltage with the LTC3626 track function. Because of the current and temperature monitoring and limiting capabilities of the LTC3626, the 1768A input or output current, as well as its maximum temperature can be limited or clamped. The 1768A uses low profile surface mount components, due to the high switching frequency capability of the LTC3626, which is programmable up to 3MHz. All these features make the 1768A an ideal circuit for use in industrial applications. Design files for this circuit board are available at http://www.linear.com/demo L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. PERFORMANCE SUMMARY PARAMETER CONDITIONS VALUE Input Voltage Range 3.6V –20V Output Voltage Range 0.6V-6V Run/Shutdown GND = Shutdown VIN = Run Output Voltage Regulation VIN = 3.6V to 20V, IOUT = 0A to 2.5A 1.2V ±2% Typ. (1.176V – 1.224V) VIN = 3.6V to 20V, IOUT = 0A to 2.5A 1.8V ±2% Typ. (1.764V – 1.836V) VIN = 4V to 20V, IOUT = 0A to 2.5A 3.3V ±2% Typ. (3.234V – 3.366V) Typical Output Ripple Voltage VIN = 12V, VOUT = 1.8V IOUT = 2.5A (20MHz BW) < 20mVP-P Burst Mode-to-Continuous Mode Transition Current Values VIN = 12V, VOUT = 1.2V IOUT < 680mA VIN = 12V, VOUT = 1.8V IOUT < 880mA VIN = 12V, VOUT = 3.3V IOUT < 1.2A Mode Pin = INTVCC Burst Mode Mode = GND FCM (Forced Continuous Mode) Mode Nominal Switching Frequency Mode = Floating Synchronized or Burst Mode RT = 324k 1MHz ±20% RT connected to INTVCC 2MHz ±30% dc1768af 1 DEMO MANUAL DC1768A QUICK START PROCEDURE Demonstration Circuit 1768A is easy to set up to evaluate the performance of the LTC3626. 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 default locations: 1.2V position of the output voltage header JP1, the SS position of the soft-start/track header JP5, the FCM (Forced Continuous Mode) position of the MODE header JP6, the ON position of RUN header JP7, the 1MHz position of the frequency header JP8, the EXT position of the ITH header JP9, the SET/OFF position of the temperature set header JP10, the OFF position of the temp. monitoring header JP11, the OFF position of the output current monitoring header JP12, and the OFF position of the input current monitoring header JP13. 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 1768A set up according to the proper measurement configuration and equipment in Figure 1, apply 6.3V at VIN (Do not hot-plug VIN or increase VIN over the rated maximum supply voltage of 20V, 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 JP7 into the OFF position.). The output voltage should be regulating. Measure VOUT it should measure 1.2V ±1% (1.188V to 1.212V). Vary the input voltage from 3.6V to 20V and adjust the load current from 0 to 2.5A. VOUT should regulate around 1.2V ±2% (1.176V to 1.224V). Measure the output ripple voltage; it should measure less than 20mVAC. Set the input voltage to 12V and the output current to any current less than 1.25A. Observe the discontinuous mode of operation at the switch node, and measure the output ripple voltage. It should measure less than 50mV. Change the shunt position on the MODE header from BM to FCM (Forced Continuous Mode) and observe the voltage waveform at the switch pins (the other side of the inductor from the output). Verify the switching frequency is between 850kHz and 1.2MHz (T = 1.17μs and 833ns), and that the switch node waveform is rectangular in shape. Insert the JP7 shunt into the OFF position and move the shunt in the 1.2V output JP1 header into any of the two remaining output voltage option headers: 1.8V (JP2) or 3.3V (JP3). Just as in the 1.2V VOUT test, the output voltage should read VOUT ±1% tolerance under static line and load conditions and ±1% tolerance under dynamic line and load conditions ±2% total). Also, the circuit operation in discontinuous mode will be the same. Monitor the input and output currents, and the die temperature, by changing the shunts on headers JP13, JP12, and JP11, respectively. The currents and temperature can even be limited using headers JP13, JP12, and JP10 – the TSET header, and adjusting the values of resistors R12, R13, and R14 (Consult the Input/Output Current and OnDie Temperature Monitor and Limit section of the LTC3626 datasheets for more details.). When finished, turn off the circuit by inserting the shunt in header JP7 into the OFF position. dc1768af 2 DEMO MANUAL DC1768A QUICK START PROCEDURE Table 1. Jumper Description JUMPER FUNCTION RANGE/SETTING (DEFAULT) JP1 Output Voltage Setting. 1.2V JP5 Soft-Start (TRACK or SS) TRACK – (SS) JP6 MODE/SYNC: Forced Continuous Mode (FCM), Burst Mode, or SYNC (FCM) – BM – SYNC JP7 RUN (ON) – OFF JP8 Frequency (FREQ) (1MHz) – 2MHz JP9 ITH: External Comp. (EXT) or Internal (INTVCC) Comp. (INT) (EXT) – INT JP10 Temperature Setting (TSET): Externally Set (EXT SET) or Internally Set (INTVCC) or Off (SET/OFF) EXT SET – (SET/OFF) JP11 Temperature Monitoring (TMON) ON – (OFF) JP12 Output Current Monitoring (IOUT) ON – (OFF) JP13 Input Current Monitoring (IIN) ON – (OFF) dc1768af 3 DEMO MANUAL DC1768A QUICK START PROCEDURE IIN + – IOUT + + + VS – – VIN + – VOUT – + LOAD – Figure 1. Proper Equipment Measurement Set-Up GND VIN Figure 2. Measuring Input or Output Ripple dc1768af 4 DEMO MANUAL DC1768A QUICK START PROCEDURE Normal Switching Frequency and Output Ripple Voltage Waveforms Figure 3. Switch Node Voltage, Output Ripple Voltage & Inductor Ripple Current Waveforms VIN = 12V, VOUT = 3.3V, IOUT = 2.5A, fSW = 1MHz Trace 1: Switch Voltage (10V/DIV) Trace 2: Output Ripple Voltage (20mV/DIV AC) Trace 4: Inductor Ripple Current (2A/DIV) Load Step Response Waveforms Figure 4. Load Step Response VIN = 12V. VOUT = 1.2V, 2.5A Load Step (0A-2.5A) Forced Continuous Mode, fSW = 1MHz. Trace 2: Output Voltage (20mV/DIV AC) Trace 4: Output Current (1A/DIV) dc1768af 5 DEMO MANUAL DC1768A QUICK START PROCEDURE Load Step Response Waveforms Figure 5. Load Step Response VIN = 12V, VOUT = 1.8V, 2.5A Load Step (0A-2.5A) Forced Continuous Mode fSW = 1MHz Trace 2: Output Voltage (50mV/DIV AC) Trace 4: Output Current (1A/DIV) Load Step Response Waveforms Figure 6. Load Step Response VIN = 12V, VOUT = 3.3V, 2.5A Load Step (0A-2.5A) Forced Continuous Mode fSW = 1MHz Trace 2: Output Voltage (50mV/DIV AC) Trace 4: Output Current (1A/DIV) dc1768af 6 DEMO MANUAL DC1768A QUICK START PROCEDURE Figure 7. Input and Output Current Monitoring VIN = 12V, IIN = 620mA, VOUT = 3.3V, IOUT = 2A, fSW = 1MHz Trace 1: IOUTMON Voltage (0.5V/DIV) Trace 2: IINMON Voltage (0.1V/DIV) Trace 3: IOUT Current (2A/DIV) Trace 4: IIN Current (500mA/DIV) With a Current Sense Resistor of 4.02k Connected to Both The Input and Output Current Monitors, Their Voltages Equate to: VIOUTMON = 2A/16000 × 4.02k = 0.503V VINMON = 620mA/16000 × 4.02k = 0.156V 95 Vo = 3.3V 80 Vo = 1.8V Vo = 1.2V Efficiency (%) 65 50 35 20 1.00E-03 1.00E-02 1.00E-01 Load Current (A) 1.00E+00 1.00E+01 Figure 8. Efficiency Graph VIN = 12V, Burst Mode, fSW = 1MHz L:1 μH Vishay IHLP-2020BZ-ER-1R0-MO1 dc1768af 7 DEMO MANUAL DC1768A PARTS LIST ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Cap., NP0, 220pF, 25V, 10%, 0402 AVX, 04023A221KAT2A Required Circuit Components 1 1 CITH 2 1 C1 Cap., X5R, 2.2μF, 16V, 20%, 0603 TDK, C1608X5R1C225M 3 2 C3, C6 Cap., X7R, 22μF, 25V, 20%, 1210 MURATA, GRM32ER71E226M 4 1 C4 Cap., X5R, 47μF, 6.3V, 20%, 1206 Taiyo Yuden, JMK316BJ476ML-T 5 1 C5 Cap., NP0, 22pF, 50V, 10% 0402 AVX, 04025A220KAT 6 1 C8 Cap., X7R, 0.1μF, 25V, 10% 0603 TDK, C1608X7R1E104K 7 1 C11 Cap., X5R, 1μF, 6.3V, 10% 0402 AVX, 04026D105KAT2A 8 1 L1 Inductor, 1.0μH IHLP-2020BZ-01 Vishay IHLP-2020BZER1R0M01 9 1 RITH Res., Chip, 13k, 0.06W, 5% 0402 VISHAY, CRCW040213K0JNED 10 2 R3, R4 Res., Chip, 115k, 0.06W, 1% 0402 VISHAY, CRCW0402115KFKED 11 1 U1 IC. LTC3626EUDC, 3 × 4mm, 20 QFN LINEAR TECH., LTC3626EUDC#PBF Additional Demo Board Circuit Components 12 0 CC(OPT) Cap., 0402 13 1 C2 Cap., Tant. 3.3μF, 35V, 20%, 6032 14 0 C7, C10(OPT) Cap., 1206 15 1 C9 Cap., X7R, 2200pF, 25V, 20%, 0402 AVX, 04023C225MAT 16 2 C12, C13 Cap., X5R, 1μF, 25V, 10%, 0603 TDK, C1608X5R1E105K 17 0 C14(OPT) Cap., 1812 18 1 C15 Cap., X5R, 0.33μF, 25V, 20%, 0603 19 0 D1(OPT) Schottky Diode, SOD-323 AVX, TAJW335M035R AVX, 06033D334MAT 20 2 R10, RON Res., Chip, 0Ω, 0.06W, 0402 VISHAY, CRCW04020000Z0ED 21 1 R1 Res., Chip, 100k, 0.06W, 5%, 0402 VISHAY, CRCW0402100KFKED 22 1 R2 Res., Chip, 324k, 0.06W, 1%, 0402 NIC, NRC04F3243TRF 23 1 R5 Res., Chip, 57.6k, 0.06W, 1%, 0402 VISHAY, CRCW040257K6FKED 24 1 R6 Res., Chip, 25.5k, 0.06W, 1%, 0402 VISHAY, CRCW040225K5FKED 25 0 R7, R9, R14(OPT) Res., 0402 26 2 R8, R11 Res., Chip, 1M, 0.06W, 5%, 0402 VISHAY, CRCW04021M00JNED 27 2 R12, R13 Res., Chip, 4.02k, 0.06W, 1%, 0402 VISHAY, CRCW04024K02FKED 28 1 R17 Res., Chip,10Ω, 0.06W, 5%, 0402 VISHAY, CRCW040210R0JNED Hardware: For Demo Board Only 29 13 E1-E13 Turret,Testpoint Mill Max2501-2-00-80-00-00-07-0 30 4 JP1, JP2, JP3, JP4 2 PIN 0.079 SINGLE ROW HEADER SAMTEC, TMM102-02-L-S 31 1 JP5 2X2, 0.079 DOUBLE ROW HEADER SAMTEC, TMM102-02-L-D 32 1 JP6 2X3, 0.079 DOUBLE ROW HEADER SAMTEC, TMM103-02-L-D 33 7 JP7-JP13 3 PIN 0.079 SINGLE ROW HEADER SAMTEC, TMM103-02-L-S 34 10 XJP1, XJP5-XJPP13 SHUNT, .079" CENTER SAMTEC, 2SN-BK-G 35 4 MH1-MH4 STAND-OFF, NYLON 0.25" KEYSTONE, 8831(SNAP ON) dc1768af 8 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. 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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 dc1768af 10 Linear Technology Corporation LT 1012 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2012