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