DEMO MANUAL DC236 DESIGN-READY SWITCHERS LTC1628 2-Phase Constant-Frequency Synchronous, Dual-Output DC/DC Converter U DESCRIPTIO This demonstration board provides 3.3V/4A and 5V/4A and 3.3V/25mA linear regulators are also included. In the outputs using a low EMI, 2-phase, adjustable, dual switch- optional standby mode, these internal regulators are ca- ing regulator controller. This design is ideally suited for pable of powering external system wake-up circuitry when notebook computer system power supply applications. both high current controllers are shut down. Two low TM Operating the two high side MOSFETs 180 out of phase current modes of operation are available: Burst Mode significantly reduces peak input ripple current, thereby operation offers highest efficiency while Burst Disable reducing radiated and conducted EMI. External parts mode provides constant-frequency operation down to 1% count, cost and size are minimized in this design. Output of maximum designed load. The frequency is externally voltages can be externally set to as low as 0.8V. The DC-controlled over a 130kHz to 300kHz range. The con- controllers have overcurrent latch-off, which can be exter- troller can operate at up to 99% duty cycle for very low nally defeated, as well as internal current foldback for dropout conditions. The demonstration board operates on overload situations. The overcurrent latch-off on one an input supply of from 5.2V to 30V. Refer to the LTC 1628 controller can be configured to shut off the other output. data sheet for other possible configurations. Gerber files A soft latch for overvoltage conditions is also provided. In for this circuit board are available. Call the LTC factory. , LTC and LT are registered trademarks of Linear Technology Corporation. addition to the two high current outputs, on-chip 5V/50mA Burst Mode is a trademark of Linear Technology Corporation. WWU W PERFOR A CE SU ARY Operating Temperature Range: 0 C to 50 C (continued on Page 2) Input Voltage Range Input Voltage Limited by External MOSFET Drive and Breakdown Requirements 5.2V to 30V Outputs Output Voltage: Controller 1 Externally Adjustable 0 to 3A, 4A Pk 5V 0.10V Output Voltage: Controller 2 Externally Adjustable 0 to 3A, 4A Pk 3.33V 0.067V 5V Linear Regulator 5V 4% 3.3V Linear Regulator 3.3V 4% Typical Output Ripple at 10MHz BW 300kHz I = 1A 3.3V and 5V Outputs V = 15V 20mV O IN P-P W U U TYPICAL PERFOR A CE CHARACTERISTICS A D BOARD PHOTO Demo Circuit 236A Efficiency vs Load 100 5V OUTPUT 90 3.3V OUTPUT 80 70 60 V = 15V IN 50 0.001 0.01 0.1 1 10 OUTPUT CURRENT (A) DC236TP01 DC236 BP 1 EFFICIENCY (%) DEMO MANUAL DC236 DESIGN-READY SWITCHERS WWU W PERFOR A CE SU ARY Operating Temperature Range: 0 C to 50 C (continued from Page 1) Frequency FREQSET Pin Tied to INTV Pin 300kHz CC Line Regulation V = 7V to 20V 3.3V and 5V Outputs 1mV IN Load Regulation I = 0 to 3A 3.3V and 5V Outputs 20mV O Supply Current V = 15V, 5V and 3.3V On, EXTV = V 390m A IN CC OUT1 Shutdown Current V = 15V, STBYMD = 0V 20m A IN Standby Current 5V INTV and 3.3V LDO On V = 15V, RUN/SS1 and RUN/SS2 = 0V, 1MW STBYMD to V 125m A CC IN IN Efficiency V = 15V, 5V at 3A and 3.3V at 3A 94% IN QUICK START GUIDE This demonstration board is easily set up to evaluate the 4. Connect the input power supply to the V and GND IN performance of the LTC1628. Please follow the proce- terminals on the right, center of the board. Do not dure outlined below for proper operation. increase V over 30V or the MOSFETs may be dam- IN aged. The recommended V to start is < 7V. IN 1. Refer to Figure 1 for board orientation and proper measurement equipment setup. 5. Switch on the desired channel(s) by removing the RUN/SS1 or RUN/SS2 jumper. 2. Place the jumpers as shown in the diagram. Tempo- rarily leave off the STBYMD and FCB jumpers. 6. Measure V and V to verify output voltages of OUT1 OUT2 5V 0.1V and 3.3V 0.067V, respectively, at load 3. Connect the desired loads between V , V and OUT1 OUT2 currents of up to 3A each. their closest PGND terminals on the board. The loads can be up to 4A for V and 4A for V . Soldered 7. Active loads can cause confusing results. Refer to OUT1 OUT2 wires should be used when the load current exceeds the active load discussion in the Operation section. 1A in order to achieve optimum performance. WW U EASURE E T SETUP 5V The circuit shown in Figure 2 provides fixed voltages of 5V V V LOAD OUT1 and 3.3V at currents of up to 4A. Figure 1 illustrates the A correct measurement setup in order to verify the typical numbers found in the Performance Summary table. Small 1 0 GND 5V L1 spring clip leads are very convenient for small-signal RUN/SS1 bench testing but should not be used at the current and FLTCPL V IN A + FREQ impedance levels associated with this switching regulator. V V IN STBYMD Soldered wire connections are required to properly ascer- GND FCB tain the performance of this demonstration PC board. Do RUN/SS2 L2 not tie the grounds together off the test board. GND 3.3V The six jumpers on the left side of the board are settable A as follows: the center pin is connected to ground when the 3.3V V V LOAD OUT2 jumper is in the rightmost position. The center pin is DC236 F01 connected to a positive bias source when the jumper is in the leftmost position. Figure 1. Proper Measurement Setup 2 LTC1628 MULTI-PHASE SYSTEM POWER DEMO CIRCUIT DC236