QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 993 500MA, 2.25 MHZ SYNCHRONOUS STEP-DOWN REGULATOR LTC3542 DESCRIPTION Demonstration circuit 993A is a step-down converter, applications, the DC993A is a high efficiency circuit - using the LTC3542 monolithic synchronous buck regula- over 90% in some cases. The DC993A consumes only tor. The DC993A has an input voltage range of 2.5V to 27 uA during sleep mode operation, and during shut- 5.5V, and is capable of delivering up to 500 mA of output down, it consumes at less than 1 uA. Because of the current in a small 2x2 mm DFN package. The output high switching frequency of the LTC3542 nominal 2.25 voltage of the DC993A can be set as low as 0.6V, the MHz - the DC993A uses low profile surface mount com- reference voltage of the LTC3542. At low load currents, ponents. These features, plus the LTC3542 coming in a the DC993A can operate in either noise sensitive applica- either a tiny 2x2 mm 6-Lead DFN package or a small 6- tions, due to the capability of the LTC3542 to operate in Lead SOT package, make the DC993A an ideal circuit for pulse-skipping mode, or in high efficiency applications, use in battery-powered, hand-held applications. Gerber because the LTC3542 can also operate in Burst Mode. files for this circuit are available. Call the LTC Fac- Of course, in continuous mode, or large load current tory. Table 1. Performance Summary (T = 25C) A PARAMETER CONDITIONS VALUE Minimum Input Voltage 2.5V Maximum Input Voltage 5.5V GND = Shutdown Run/Shutdown V = Run IN 1.2V 4% (1.152V 1.248V) Output Voltage V V = 2.5V to 5.5V, I = 0A to 500 mA 1.5V 4% (1.44V - 1.56V) OUT IN OUT 1.8V 4% (1.728V 1.872V) Typical Output Ripple V V = 5V, I = 500 mA (20 MHz BW) < 20mV OUT IN OUT PP Line 1% Output Regulation Load 1% Nominal Switching Frequency 2.25 MHz Burst Mode - V = 3.6V, V = 1.8V ~60 mA 10 mA IN OUT Operation Modes Pulse-Skip - V = 3.6V, V = 1.8V ~60 mA 10 mA IN OUT 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 993 500MA, 2.25 MHZ SYNCHRONOUS STEP-DOWN REGULATOR QUICK START PROCEDURE Demonstration Circuit 993 is easy to set up to evalu- be regulating. Measure Vout - it should measure ate the performance of the LTC3542. For proper 1.2V +/- 2% (1.176V to 1.224V). measurement equipment configuration, set up the Vary the input voltage from 2.5V to 5.5V and adjust circuit according to the diagram in Figure 1. Before the load current from 0 to 500 mA. Vout should read proceeding to test, insert shunts into the OFF position between 1.2V +/- 4% (1.152V to 1.248V). of header JP3, which connects the RUN pin to ground Measure the output ripple voltage at any output cur- (GND), and thus, shuts down the circuit, and the 1.2V rent level it usually will measure less than 30 mVAC. output voltage header JP4. Observe the voltage waveform at the switch node. When measuring the input or output voltage ripple, Verify the switching frequency is between 1.8 MHz care must be taken to avoid a long ground lead on the and 2.7 MHz (T = 0.555 us and 0.37 us), and that the oscilloscope probe. Measure the input or output volt- switch node waveform is rectangular in shape. age ripple by touching the probe tip directly across the Vin or Vout and GND terminals. See Figure 2 for Insert header JP3 shunt into the OFF position and move proper scope probe measurement technique. the 1.2V Vout shunt into any of the two remaining output voltage option headers: 1.5V or 1.8V. Just as in the With the DC993 set up according to the proper meas- 1.2Vout test, the output voltage should read Vout +/- 2% urement and equipment in Figure 1, apply 3.3V at Vin tolerance under static line and load conditions, and +/- (Do not hot-plug Vin or increase Vin over the rated 1% tolerance under dynamic line and load conditions maximum supply voltage of 5.5V, or the part may be (+/- 2% total). damaged.). Measure Vout it should read 0V. If de- sired, one can measure the shutdown supply current When finished, turn off the circuit by inserting the at this point. The supply current will be approxi- shunt in header JP3 into the OFF position (connecting mately 1 uA, or less, in shutdown. the RUN pin to ground). Turn on the circuit by inserting the shunt in header JP3 into the ON position. The output voltage should 2