QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 457B MULTI-PHASE SYSTEM POWER SUPPLY LTC3727-1 DESCRIPTION Demonstration circuit 457B features the LTC3727-1 in a rent outputs, on-chip 7.5V/50mA and 3.3V/25mA linear dual output5V/4A and 12V/3Alow EMI, 2-phase, regulators are also included. In the optional standby adjustable, dual switching regulator controller applica- mode, these internal regulators are capable of powering tion. external system wake-up circuitry when both high cur- rent controllers are shut down. Two light load modes of Operating the two high side MOSFETs 180 degrees out operation are available: Burst Mode operation offers of phase significantly reduces peak input ripple current highest efficiency, whereas burst disable mode provides thereby reducing radiated and conducted EMI. External low noise, constant frequency operation down to 1% of parts count cost and size are minimized in this design. maximum designed load. The controller can operate at Both controllers have overcurrent latch-off, which can be up to 99% duty cycle for very low dropout capability. externally disabled, as well as internal current foldback for overload situations. A soft latch for overvoltage con- Design files for this circuit board are available. Call ditions is also provided. In addition to the two high cur- the LTC factory. Table 1. Performance Summary (Operating Temperature Range: 0C to 50C) PARAMETER CONDITION VALUE Input Voltage Range If the input voltage must exceed 25V, use higher voltage rating input capacitors and MOS- 15V to 25V FETs. The IC works up to 36V. If 12V, 3A is needed for lower than 15V input voltage, reduce the sense resistor value. Outputs V = 5V, 0A to 4A 5V 3% OUT1 V = 12V, 0A to 3A 12V 3% OUT2 7.5V Linear Regulator 7.5V 4% 3.3V Linear Regulator 3.3V 4% Typical Output Ripple (V ) 10MHz BW, 4A load, V = 15V, frequency = 530kHz 20mV OUT1 IN P-P Typical Output Ripple (V ) 10MHz BW, 3A load, V = 15V, frequency = 530kHz 10mV OUT2 IN P-P Typical Operating Frequency PLLLPF pin tied to 3.3V 530kHz Efficiency V = 15V, 5V at 4A, 12V at 3A 96% IN QUICK START PROCEDURE Demonstration circuit 457B is easy to set up to evaluate NOTE: The maximum load at 5V is 4A, and the maxi- the performance of the LTC3727-1. Refer to Figure 1 for mum at 12V is 3A. Soldered wires should be used proper measurement equipment setup and follow the when the load current exceeds 1A in order to achieve procedure below: optimum performance. 1. Place RUNSS1 and RUNSS2 in OFF position, the 3. Connect the input power supply to the VIN and GND FREQ jumper at the selected frequency and the FCB terminals on the right, center of the board. jumper in GND position. NOTE: Do not increase V over 25V. If the input volt- IN 2. Connect the desired loads between 5V and 12V termi- age must exceed 25V, use higher voltage rating input nals and their closest PGND terminals on the board. capacitors and MOSFETs. The IC works up to 36V. If 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 457B MULTI-PHASE SYSTEM POWER SUPPLY 12V, 3A is needed for lower than 15V input voltage, 5. Measure the output voltages. They should be 5V reduce the sense resistor value. 0.1V and 12V 0.24V respectively, at each specified load current. 4. Switch on the desired channel(s) by removing the RUN/SS1 and/or RUN/SS2 jumper. LOAD + + + LOAD Figure 1. Proper Measurement Equipment Setup 2 + + + + + +