DEMO MANUAL DC1852A LTC3536 1A, Low Noise, Wide V IN Buck-Boost DC/DC Converter DESCRIPTION Demonstration circuit 1852A is a combined step-up and The DC1852A consumes less than 28A of quiescent cur- step-down DC/DC converter, using the LTC3536 monolithic rent during Burst Mode operation, and during shutdown, synchronous buck-boost regulator. The DC1852A has it consumes less than 1A. The DC1852A has a standard wide input voltage range of 1.8V to 5.5V and is capable of operating frequency of 1MHz, but can be adjusted to delivering up to 1A of output current. The output voltage frequencies as high as 2MHz. If Pin 1 (RT) is tied to V , IN of the DC1852A can be set as low as 1.8V and can go as the default switching frequency is 1.2MHz. Because of high as 5.5V. DC1852A supports two operation modes: the high switching frequency of the DC1852A, small, low fixed-frequency pulse-width modulation (PWM) and profile surface mount components are used in the circuit. BurstMode operation. Fixed-frequency mode of opera- These features, plus the LTC3536s small 12-lead MSOP tion maximizes the output current, reduces output voltage package, make the DC1852A a perfect match for battery- ripple, and yields a low noise switching spectrum. Burst powered, handheld applications. Mode operation employs a variable frequency switching Design files for this circuit board are available at algorithm that minimizes the no-load input quiescent cur- DEMO MANUAL DC1852A QUICK START PROCEDURE Demonstration circuit 1852A is easy to set up to evaluate 2. Turn on the circuit by inserting the shunt in header the performance of the LTC3536. For proper measurement JP2 into the ON position. The output voltage should be equipment configuration, set up the circuit according to regulating. Measure V it should measure 3.3V 1% OUT the diagram in Figure 1. Before proceeding to test, insert (Do not apply more than the rated maximum voltage shunts into JP1 FIXED FREQ and JP2 OFF positions, which of 5.5V to the board or the part may be damaged). connects the RUN pin to ground (GND), and thus, shut 3. Vary the converter load, which should not exceed 1A down the circuit. at V 5V. IN NOTE: When measuring the input or output voltage ripple, 4. Vary the input voltage from 1.8V to 5.5V, the available care must be taken to avoid a long ground lead on the output current depends on the input voltage, see oscilloscope probe. Measure the input or output voltage LTC3536 data sheet for details. ripple by touching the probe tip directly across the V or IN 5. Set output current to zero and move jumper JP2 into V and GND terminals. See Figure 2 for proper scope OUT Burst Mode position and measure V it should probe technique. OUT register 3.3V 1%. 1. With the DC1852 set up according to the proper mea- 6. Vary the input voltage from 1.8V to 5.5V, the available surement and equipment in Figure 1, apply 5V at V . IN output current depends on the input voltage. Load in Measure V it should read 0V. If desired, one can OUT Burst Mode should no exceed 0.15A at V 5V and 0.1A measure the shutdown supply current at this point. IN at 2.5V, see LTC3536 data sheet for details. The supply current will be approximately 3A, or less, in shutdown. + + Figure 1. Proper Measurement Equipment Setup dc1852af 2