QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 799 SYNCHRONOUS BUCK-BOOST CONVERTER WITH AUTOMATIC BURST MODE LTC3442EDE DESCRIPTION Demonstration Circuit 799 is a high efficiency syn- The LTC3442 has manual or programmable Auto- chronous Buck-Boost converter using the LTC3442. matic Burst Mode operation and programmable aver- The input range is from 2.4V to 5.5V, making it ideal age input current limit. for single-cell Lithium-Ion or three-cell NiCd/NiMH When using long wire connections to the input battery applications. This converter provides up to source (such as wall adaptors), there can be input 95% efficiency, much higher than traditional Buck- over voltage transients during initial plug-in. C2 is Boost converters. For 2.7V minimum input voltage, installed on DC799 to damp the possible voltage this converter can provide up to 1.2A load current. transients. C2 is not needed for any application when The output voltage is set at 3.3V. A different output the input source is close to the regulator. Please refer voltage in the range of 2.4V to 5.25V can be obtained to Application Note 88 for details. by changing one of the feedback resistors. The Design files for this circuit board are available. Call switching frequency is set at 1MHz, which is a good the LTC factory. trade-off between efficiency and size. Adjusting RT LTC is a trademark of Linear Technology Corporation can program the frequency between 300kHz to 2MHz. In shutdown, the IC itself draws less than 1mA. Table 1. Performance Summary (T = 25C unless otherwise noted) A PARAMETER CONDITION VALUE Minimum Input Voltage -40C to 85C 2.4V Maximum Input Voltage -40C to 85C 5.5V Output Voltage V V = 2.5V to 5.5V, I = 0A to 1.1A 3.3V 4% OUT IN OUT Maximum Output Current V = 2.5V 1.1A IN Maximum Output Current V = 2.7V 1.2A IN Typical Output Ripple V V = 3.6V, I = 1.1A (20MHz BW) 45mV OUT IN OUT PP Typical Switching Frequency RT=43.2K 1MHz V = 4.2V, I = 0.2A 93% Typical IN OUT Efficiency (Fixed Frequency Mode) V = 4.2V, I = 1.0A 90% Typical IN OUT Off (40C to 85C) 0.4V MAX On/Off Control On (-40C to 85C) 1.4V MIN QUICK START PROCEDURE Demonstration circuit 799 is easy to set up to evalu- for proper measurement equipment setup and follow ate the performance of the LTC3442. Refer to Figure 1 the procedure below: 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 799 SYNCHRONOUS BUCK-BOOST CONVERTER WITH AUTOMATIC BURST MODE NOTE: When measuring the input or output voltage 3. Turn on the power at the input. ripple, care must be taken to avoid a long ground lead NOTE: Make sure that the input voltage does not ex- on the oscilloscope probe. Measure the input or out- ceed 5.5V. put voltage ripple by touching the probe tip directly 4. Check for the proper output voltage. Vout = 3.17V across the Vin or Vout and GND terminals. See to 3.43V. Figure 2 for proper scope probe technique. NOTE: If there is no output, temporarily disconnect 1. Place jumpers in the following positions: the load to make sure that the load is not set too high. JP1 RUN 5. Once the proper output voltage is established, ad- JP2 DISABLE just the load within the operating range and ob- JP3 AUTO ON serve the output voltage regulation, ripple voltage, efficiency and other parameters. 2. With power off, connect the input power supply to Vin and GND. GRAPHICS Figure 1. Proper Measurement Equipment Setup 2