LTC3101EUFE DEMO CIRCUIT 1598A Quick Start Guide LTC3112EDHD 15V, 2.5A Synchronous Buck-Boost DC/DC Converter DESCRIPTION Demonstration Circuit 1598A is a fixed frequency syn- demonstration board has been designed to operate chronous buck-boost converter with an extended in- with VIN from 2.7V to 15V and an output current up put and output range. The unique 4-switch, single to 2.5A. For VIN < 5V, IOUT capability is reduced. inductor architecture provides low noise and seamless VOUT is set to 5.0V. Typical demo board efficiency is operation from input voltages above, below, or equal shown below. to the output voltage. Design files for this circuit board are available. Call The LTC3112 features selectable PWM or Burst Mode the LTC factory. operation, and an easily synchronizable oscillator. An output current monitor allows the load current to be controlled or monitored. L, LTC, LTM, LT, Burst Mode, are registered trademarks of Linear Technology Corporation. The LTC3112 operates with a 2.7V to 15V input vol- All other trademarks are the property of their respective owners. tage range and a VOUT range from 2.5V to 14V. The Input Voltage Range: V 2.7V to 15.0V CC VOUT 5.0V IOUT 2.5A for VIN > 5.0V Figure 1. Typical Efficiency 1 LTC3112EDHD QUICK START PROCEDURE Using short twisted pair leads for any power con- 5. Verify VOUT is ~5.0V. nections and with all loads and power supplies off, 6. VIN can now be varied between 2.7V and refer to Figure 1 for the proper measurement and 15.0V. VOUT should remain in regulation. equipment setup. The Battery/Power Supply (PS1) 7. IOUT can also be varied from 0 to 2.5A. For should not be connected to the circuit until told to VIN < 5.0V, maximum IOUT is reduced. do so in the procedure below. This reduction is due to Iin increasing as Vin decreases. Once the input current limit is When measuring the input or output voltage ripple, reached, VOUT will fall out of regulation. care must be taken to avoid a long ground lead on the oscilloscope probe. NOTE: If VOUT drops out of regulation, check to be sure the maximum load has not been exceeded, or that VIN is not below the 1. Jumper, PS1 and LOAD Settings to start: minimum value (2.7V). PS1= OFF 8. For operation in BURST Mode move Jumper JP1 (RUN) = OFF JP2 to BURST. IOUT is limited in BURST JP2 (PWM) = 750kHz (FIXED FREQUENCY) MODE. See the datasheet for more LOAD = 1.0A / 5 10W resistor information. 2. With power OFF connect the power supply (PS1) as shown in Figure 1. If accurate current measurements are desired (for NOTE: IOUT can be monitored at the efficiency calculations for example) then IOUT/IADJ terminal. The voltage at the ter- connect an ammeter in series with the minal is: supply as shown. The ammeter is not -6 V IOUT= IOUT* 24*10 * 42.2k required however. Where 42.2k Ohms is the value of R9. See 3. Connect the load to VOUT as shown in the datasheet for more information, includ- Figure 1. Again, connect an ammeter if ing typical curves. accurate current measurement or monitoring is desired. 4. Turn on PS1 and slowly increase voltage until the voltage at VIN is 3.6V. Move Jumper JP1 to ON. 2