QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 625 1MHZ, 1A SYNCHRONOUS BUCK-BOOST CONVERTER LTC3441 DESCRIPTION Demonstration Circuit 625 is a constant-frequency syn- frequency at the MODE/SYNC pin can also synchronize chronous Buck-Boost converter using the LTC3441. The the switching frequency between 1.15MHz to 1.7MHz. input range is from 2.4V to 5.5V, making it ideal for sin- In shutdown, the IC draws less than 1A. gle-cell lithium-ion or three-cell NiCd/NiMH battery ap- When using long wire connections to the input sources plications. This converter provides up to 95% efficiency, (such as wall adaptors), there can be input over voltage much higher than traditional Buck-Boost converters. For transients during initial plug-in. C8 is installed on 2.5V minimum input voltage, this converter can provide DC625 to damp the possible voltage transients. C8 is up to 1A load current. not needed for any application when input source is The output voltage is set at 3.3V. A different output volt- close to the regulator. Please refer to Application Note age in the range of 2.4V to 5.25V can be obtained by 88 for details. changing one of the feedback resistors. The switching Design files for this circuit board are available. Call frequency is set at 1MHz, which is a good trade-off be- the LTC factory. tween efficiency and size. Applying twice the desired Table 1. Performance Summary (T = 25C unless otherwise noted) A PARAMETER CONDITION VALUE 2.4V (2.5V minimum input for 1A Minimum Input Voltage -40C to 85C load) Maximum Input Voltage -40C to 85C 5.5V Output Voltage V V = 2.5V to 5.25V, I = 0A to 1A 3.3V 3% OUT IN OUT Maximum Output Current V = 2.5V to 5.25V 1A IN Typical Output Ripple V V = 3.0V, I = 1A (20MHz BW) 40mV OUT IN OUT PP Typical Switching Frequency 1MHz V = 4.2V, I = 0.2A 94% Typical IN OUT Efficiency V = 4.2V, I = 1A 89% Typical IN OUT Logic Low Voltage-Off, -40C to 85C 0.4V MAX On/Off Control Logic High Voltage-On 2.4V MIN QUICK START PROCEDURE Demonstration circuit 625 is easy to set up to evaluate NOTE: When measuring the input or output voltage ripple, the performance of the LTC3441. Refer to Figure 1 for care must be taken to avoid a long ground lead on the proper measurement equipment setup and follow the oscilloscope probe. Measure the input or output voltage procedure below: ripple by touching the probe tip directly across the Vin 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 625 1MHZ, 1A SYNCHRONOUS BUCK-BOOST CONVERTER or Vout and GND terminals. See Figure 2 for proper NOTE: Make sure that the input voltage does not ex- scope probe technique. ceed 5.5V. 1. Place jumpers in the following positions: 4. Check for the proper output voltage. Vout = 3.2V to 3.4V. JP1 RUN NOTE: If there is no output, temporarily disconnect the load to make sure that the load is not set too high. JP2 FIXED FREQ. 5. Once the proper output voltage is established, adjust 2. With power off, connect the input power supply to Vin the load within the operating range and observe the and GND. output voltage regulation, ripple voltage, efficiency 3. Turn on the power at the input. and other parameters. Figure 1. Proper Measurement Equipment Setup 2