DEMO CIRCUIT 952 QUICK STARTLTC3810 GUIDE LTC3810 Current Mode Synchronous Switching Regulator Controller DESCRIPTION Demonstration circuit 952 is a current mode synchronous switching regulator featuring the LTC3810. The circuit is configured as a synchronous step-down regulator operating at 230kHz switching frequency. Output voltage is 12V at 6A maximum load. The input voltage range is 13V – 80V. The operating mode can be selected with jumper JP1. Depending on the position of this jumper, at low load the circuit will operate in forced continuous mode (for best load transient response at low current) or in pulse skip mode (for best efficiency at low current). With jumper JP1 in the mid position the circuit can synchronize to an external clock signal on the Mode/Sync pin. PERFORMANCE SUMMARY SYMBOL VIN VOUT IOUT IQ IIN PARAMETER Input Supply Range Output Voltage Output Current Input Current In Shutdown VIN Current In Pulse Skip Mode (No Load) IIN VIN Current In Forced Continuous Mode (No Load) Efficiency Efficiency A Power Good output is provided. The PGOOD output is normally high, with a pull up resistor to VLOGIC. If the output voltage is not within ± 10% of nominal value the PGOOD signal will go low. The circuit can be synchronized to an external clock signal. Design files for this circuit board are available. Call the LTC factory. L, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and PolyPhase are registered trademarks of Linear Technology Corporation. Adaptive Power, C-Load, DirectSense, Easy Drive, FilterCAD, Hot Swap, LinearView, µModule, Micropower SwitcherCAD, Multimode Dimming, No Latency ∆Σ, No Latency Delta-Sigma, No RSENSE, Operational Filter, PanelProtect, PowerPath, PowerSOT, SmartStart, SoftSpan, Stage Shedding, SwitcherCAD, ThinSOT, UltraFast and VLDO are trademarks of Linear Technology Corporation. Other product names may be trademarks of the companies that manufacture the products. Specifications are at TA = 25°C CONDITIONS VIN = 24V, ILOAD = 100mA VIN = 24V VIN = 24V, RUN/SS = 0V VIN = 24V, VFCB = INTVCC, No Load VIN = 24V, VFCB = 0V, No Load VIN = 24V, IOUT = 6A MIN 13 11.8 0 TYP 12 288 3.5 MAX 80 12.2 6 648 UNITS V V A µA mA 26 mA 96.4 % OPERATING PRINCIPLES The LTC3810 is a synchronous step-down switching regulator controller that can directly step down voltages from up to 100V input, making it ideal for telecom and automotive applications. cycles with accurate cycle-by-cycle current limit without requiring a current sense resistor. The current limit is adjustable and the operating frequency is selected by an external resistor. The LTC3810 uses a constant on-time valley current control architecture to deliver very low duty The LTC3810 has a precise (0.5%) internal reference, a 25MHz error amplifier, large gate drivers, 1 LTC3810 programmable softstart, a shutdown pin, a Sync input and a Power Good output. The LTC3810 has a flexible bias regulator circuit that can be configured in many different ways to fit the application. The 10V bias regulator can control an external series transistor that allows the bias voltage to be generated from the input voltage. The demo board provides different footprints for this external series transistor. An internal low dropout regulator can be used to provide the bias voltage if a 6.7V…15V voltage source is available. For example, in Demonstration Circuit 952 the bias voltage is generated from the input voltage during startup and from the output voltage during normal operation. The demonstration circuit can be configured to use current sense resistor by moving a couple of zero ohm resistors to different locations. EQUIPMENT 4 DMMs 1 DC Supply 0-80V capable of delivering at least 85W 1 Adjustable load 0-6A QUICK START PROCEDURE Demonstration circuit 952 is easy to set up to evaluate the performance of the LTC3810. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below: 1. Place jumpers in the following positions: JP1 Forced continuous mode operation JP2 ON 2. With power off, connect the input power supply to Vin and GND. 3. Set the power supply to 24V and turn on the power at the input. NOTE. Make sure that the input voltage does not exceed 80V. 4. Check for the proper output voltage. Vout = 11.8V to 12.2V. NOTE. If there is no output, temporarily disconnect the load to make sure that the load is not set too high. 5. Once the proper output voltages are established, adjust input voltage and load within the operating range and observe the output voltage regulation, ripple voltage, efficiency and other parameters. 2 LTC3810 Figure 1. Proper Measurement Equipment Setup 3 TP3 TP11 SYNC FORCE CONTINUOUS SS/TRACK INTVCC TP4 MODE/SYNC TP10 R6 100K R2 OPT 0 R3 1000pF CSS R17 OPT 2 3 JP1 MODE/SYNC INTVCC PULSE SKIP PGOOD VLOGIC 4 1 OPT 10K CC4 RC2 OFF ON JP2 2 INTVCC 0.01uF CC3 SHUTDOWN R1 OPT 90.9K 1% 220pF RFB2 1K 1% RC 33pF CC2 CC1 R5 OPT INTVCC R4 0 UVIN SDB SGND 1% OPT 33.2K 1% OPT RF 470K VIN R8 0 VOUT SS_TRACK PLL_LPF VFB ITH MODE_SYNC PGOOD VRNG VON NC NC ION RUV1 RUV2 RFB1 14K CF 14 13 12 11 10 9 8 7 6 5 4 3 2 1 U1 LTC3810EG 100pF CON R19 OPT INTVCC RON 274K 1% 15 16 17 18 19 20 21 22 23 24 25 26 27 28 R18 OPT NDRV EXTVCC INTVCC DRVCC BG BGRTN SENSE- NC NC NC SENSE+ SW TG BOOST 1uF C1 OPT C8 R15 0 R14 OPT R9 VIN 0 VOUT 0 R13 BG TG 0 R24 Tuesday, February 05, 2008 DESIGNER ENGINEER APPROVED CHECKED DRAWN MI APPROVALS CONTRACT NO. 1uF 0 OPT C2 0.1uF C6 Q3 ZXMN10A07F 0.1uF C5 1 R12 BG TG D2 BAS19W 1 INTVCC 3 R16 24.9K 1% R11 OPT R10 VIN 4 0 R21 08/22/05 DATE 4 Q5 OPT 4 Q4 OPT R22 0.012 1% 4 VIN Q6 OPT 4 REV Q2 Si7852DP R23 0.012 1% Q1 Si7852DP OPT R20 1 VIN 3 VIN 3 2 ECO VIN + OPT OPT + VOUT CIN4 1uF 100V VCC VIN VOUT GND 12V 6A TP5 TP2 13V - 80V TP7 TP6 SHEET DC952A FILENAME: 952A-4.DSN DWG NO STEP-DOWN CONVERTER CAGE CODE 1 OF 1 REV A APPROVED GND TP1 TP8 TP9 COUT2 270uF 16V OPT 1630 McCarthy Blvd. Milpitas, CA 95035 Phone: (408)432-1900 Fax: (408)434-0507 0.1uF C7 OPT + COUT6 COUT1 270uF + 16V CIN6 CIN5 OPT C3 OPT COUT5 COUT4 10uF 16V 100V CIN2 OPT 0.1uF DATE 10/18/07 VIN C4 CIN3 1uF 100V Q8 OPT C9 + 68uF 3 TECHNOLOGY D1 COUT3 10uF B1100 16V L1 7.7uH 100V CIN1 + 68uF Q7 OPT PROD VIN REVISION HISTORY DESCRIPTION SCH, LTC3810EG, HIGH EFFICIENCY HIGH VOLTAGE SCALE: NONE SIZE TITLE 1 VIN 2 4 3 INTVCC 3 1 2 4 5 6 7 8 1 2 3 5 6 7 8 1 2 3 5 6 7 8 1 2 3 5 6 7 8 1 2 3 4 4 1 2 5 6 This circuit is proprietary to Linear Technology and s upplied for us e with Linear Technology parts. Customer Notice:Linear Technology has m ade a bes t effort to des ign a circuit that m eets custom er-supplied s pecifications ; however, it rem ains the cus tom ers responsibility to verify proper and reliable operation in the actual application, Com ponent s ubstitution and printed circuit board layout m ay significantly affect circuit perform ance or reliability. Contact Linear Applications Engineering for as sis tance. LTC3810