QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1193 TRIPLE DC/DC CONVERTER LTC3545/-1 DESCRIPTION Demonstration circuit 1193 is a triple output regulator consisting of three constant-frequency step-down converters integrated into LTC3545/-1. DC1193 has an input voltage range of 2.25V to 5.5V, with regulators capable of delivering 800mA of load current on each output. The three regulators operate independently with individual RUN pins and enter pulse skipping mode at low loads for reducing output ripple. In shutdown, the DC1193 draws less than 1uA total. The DC1193 is a very efficient circuit with efficiency reading above 90%. The LTC3545 comes in a 16-pin QFN package, which has an exposed pad on the bottomside of the IC for better thermal performance. High operating frequency of 2.25MHz allows exclusive use of the small size, low profile surface mount components. These features plus internal compensation circuits, make the DC1193 demo board an ideal circuit for use in battery-powered, hand-held applications. DC1193A-A is a demoboard for LTC3545 and DC1193A-B is a demoboard for LCT3545-1. Design files for this circuit board are available. Call the LTC factory. LTC is a trademark of Linear Technology Corporation Table 1. Performance Summary (TA = 25°C) PARAMETER CONDITIONS VALUE Minimum Input Voltage 2.25V Maximum Input Voltage 5.5V Output Voltage Regulation VOUT1 VIN = 2.25V to 5.5V, IOUT = 0A to 800mA 1.8V ±2% Typical Output Ripple VOUT1 VIN = 4V, IOUT = 800mA (20 MHz BW) <15mVP–P Output Voltage Regulation VOUT2 VIN = 2.25V to 5.5V, IOUT = 0A to 800mA 1.2V ±2% Typical Output Ripple VOUT2 VIN = 4V, IOUT = 800mA (20 MHz BW) <15mVP–P Output Voltage Regulation VOUT3 VIN = 2.25V to 5.5V, IOUT = 0A to 800mA 1.5V ±2% Typical Output Ripple VOUT3 VIN = 4V, IOUT = 800mA (20 MHz BW) <15mVP–P Nominal Switching Frequency 2.25 MHz 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1193 TRIPLE DC/DC CONVERTER QUICK START PROCEDURE Demonstration Circuit 1193 is easy to set up to evaluate the performance of the LTC3545/-1. For proper measurement equipment configuration, set up the circuit according to the diagram in Figure 1. NOTE: When measuring the input or output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. Measure the input or output voltage ripple by touching the probe tip directly across the VIN or VOUT and GND terminals. See the Measurement Equipment Set-up diagram in Figure 2 for proper scope probe technique. 1. Connect the input power supply to the VIN and GND terminals. Connect the loads between the matching VOUT and GND terminals. Refer to Figure 1 for the proper measurement equipment setup. Make sure that loads on outputs VOUT1 to VOUT3 do not exceed 800mA, on each output (all three outputs can be loaded at the same time) 2. Apply 5V at VIN and than insert RUN jumper shunts JP1 through JP3 into the ON positions. 3. Measure all four outputs VOUT1 through VOUT3; they should read 1.8V, 1.2V and 1.5V correspondingly. All output voltages should be within +/- 2% tolerance. 4. Vary the input voltage from 5.5V to 2.25V; all four output voltages should be within +/- 2% tolerance. 5. Vary the VOUT1 load current from 0 to 800mA. Each output voltage should be within a tolerance of +/- 2%. 6. Vary the VOUT2 load currents from 0 to 800mA. Each output voltage should be within a tolerance of +/- 2%. 7. Vary the VOUT3 load current from 0 to 800mA. Each output voltage should be within a tolerance of +/- 2%. 8. To turn either output off set corresponding jumper into OFF position. For DC1193A-A only To synchronize converter to external clock move jumper J4 to Sync position (contacts 1 and 2) and apply synchronization pulses in 1MHz to 3MHz frequency range to SYNC pin, see datasheet LTC3545 for details. For converter to operate in Pulse skipping mode move jumper J4 to Pulse Skip position (contacts 2 and 3). For converter to operate in Burst mode move jumper J4 into Burst position (contacts 3 and 4). Warning - If the power for the demo board is carried in long leads, the input voltage at the part could “ring”, which could affect the operation of the converter. To eliminate the ringing, insert a small tantalum capacitor (for instance, AVX part # TAJW686M010) on the pads between the input power and return terminals on the bottom of the demo board. The (greater) ESR of the tantalum will dampen the (possible) ringing voltage due to the use of long input leads. On a normal, typical PCB, with short traces, the capacitor is not needed. 2 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1193 TRIPLE DC/DC CONVERTER Figure 1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Ripple 3 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1193 TRIPLE DC/DC CONVERTER 4