QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 725 7A POLYPHASE MONOLITHIC SYNCHRONOUS BUCK REGULATOR LTC3415 DESCRIPTION Demonstration Circuit 725 is a 7A high efficiency, only. The LTC3415 can also do polyphase opera- phase lockable constant frequency buck con- tion, which allows multiple DC725s to be used in verter, incorporating the LTC3415 polyphase parallel for higher current power supplies. Since monolithic synchronous regulator. The DC725 the parallel LTC3415s can operate out-of-phase, has an input voltage range of 2.375V to 5.5V and the amount of input and output capacitance re- an output voltage range from 0.6V to 5V. The ref- quired will be minimal. The DC725 offers the erence voltage of 0.6V is +/-1% accurate, produc- three standard modes of operation: force continu- TM ing a more precise output voltage. The operating ous, pulse-skipping, and Burst-Mode , for those frequency range of the DC725 is either set by the circuits that operate during intervals of low output LTC3415 internal oscillator to 1.5 MHz, set to 1 power. Extra features include tracking, for easy MHz or 2 MHz by forcing the PLLPF pin to ground power supply sequencing, output margining, or Vin, respectively, or synchronized to an external power good, and spread spectrum operation, clock, with a range between 750 kHz and 2.25 which significantly reduces the peak switching MHz. The DC725 can deliver high power for a noise emitted from the DC725. All these features monolithic part up to 7A of output current due make the DC725 perfectly suited for high current, to the high current power switches (28 m of on- high power applications, such as notebook or state resistance) of the LTC3415. The LTC3415 desktop computers. also incorporates OPTI-LOOP compensation, so that the DC725 can be optimized with external Design files for this circuit board are avail- components to provide fast transient response able. Call the LTC factory. over a wide range of line and load conditions. However, the LTC3415 has internal compensation TM - Burst Mode is a trademark of Linear Technology Corporation for those requiring a simple high power supply 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 725 7A POLYPHASE MONOLITHIC SYNCHRONOUS BUCK REGULATOR Table 1. Performance Summary (T = 25C) A PARAMETER CONDITIONS VALUE Minimum Input Voltage 2.375V Maximum Input Voltage 5.5V 1.2V 3% (1.164V to 1.236V) 1.5V 3% (1.455V to Output Voltage V Regulation V = 2.375V to 5.5V, I = 0A to 7A OUT IN OUT 1.545V) 1.8V 3% (1.746V to 1.854V) Typical Output Ripple V V = 5V, I = 7A (20 MHz BW) <20mV OUT IN OUT PP Burst Mode - V = 3.3V, V = 1.8V <1.6A 0.1A% IN OUT Operation Modes Pulse-Skipping - V = 3.3V, V = 1.8V <1.5A 0.1A% IN OUT Forced Continuous Any Output Current Nominal Switching Frequency 1.5 MHz QUICK START PROCEDURE Demonstration Circuit 725 is easy to set up to 1. With the DC725 set up according to the evaluate the performance of the LTC3415. For proper measurement and equipment in Fig- proper measurement equipment configuration, ure 1, apply 3.3V at Vin (Do not hot-plug Vin set up the circuit according to the diagram in or increase Vin over the rated maximum sup- Figure 1. Before proceeding to test, make sure ply voltage of 5.5V, or the part may be dam- the jumper shunts are in the appropriate header aged.). Measure Vout it should read 0V. If according to the legend in Figure 1, except for desired, one can measure the shutdown sup- one exception: insert jumper JP5 shunt into the ply current at this point. The supply current off (upper) position, which connects the RUN will be approximately 10 uA, or less, in shut- pin to ground (GND), and thus, shuts down the down. circuit. 2. Turn on the circuit by inserting the shunt in NOTE: When measuring the input or output volt- header JP5 into the ON (lower) position. The age ripple, care must be taken to avoid a long output voltage should be regulating. Meas- ground lead on the oscilloscope probe. Meas- ure Vout - it should measure 1.2V +/- 1.5% ure the input or output voltage ripple by touch- (1.182V to 1.218V). ing the probe tip directly across the Vin or Vout and GND terminals. See Figure 2 for proper scope probe technique. 2