QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1040 QUAD DC/DC CONVERTER LTC3544 DESCRIPTION Demonstration circuit 1040 is a quad output regulator exclusive use of small size, low profile surface mount consisting of four constant-frequency step-down components. These features plus internal compensa- converters integrated into the LTC3544. DC1040 has tion circuits make the DC1040 demo board an ideal an input voltage range of 2.25V to 5.5V, with regula- circuit for use in battery-powered, hand-held applica- tors capable of delivering 100mA, 200mA, 200mA tions. The DC1040 design supports both versions of and 300mA of output current. The four regulators op- LTC3544: LTC3544EUD (burst mode of operation) and LTC3544BEUD (pulse skip mode of opera- erate independently with individual RUN pins and en- tion). The label on the PCB identifies which con- ter pulse skipping mode at low loads to reduce output troller is installed. ripple. In shutdown, the DC1040 draws less than 1uA total. The DC1040 is a very efficient circuit with effi- ciency greater than 90%. The LTC3544 comes in a Design files for this circuit board are available. Call 16-pin QFN package, which has an exposed pad on the LTC factory. the bottom-side of the IC for better thermal perform- LTC is a trademark of Linear Technology Corporation ance. High operating frequency of 2.25MHz allows 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 100mA 1.2V 2% IN OUT Typical Output Ripple VOUT1 V = 5V, I = 100mA (20 MHz BW) <15mV IN OUT PP Output Voltage Regulation VOUT2 V = 2.25V to 5.5V, I = 0A to 200mA 1.5V 2% IN OUT Typical Output Ripple VOUT2 V = 5V, I = 200mA (20 MHz BW) <15mV IN OUT PP Output Voltage Regulation VOUT3 V = 2.25V to 5.5V, I = 0A to 200mA 0.8V 2% IN OUT Typical Output Ripple VOUT3 V = 5V, I = 200mA (20 MHz BW) <15mV IN OUT PP Output Voltage Regulation VOUT4 V = 2.25V to 5.5V, I = 0A to 300mA 1.8V 2% IN OUT Typical Output Ripple VOUT1 V = 5V, I = 300mA (20 MHz BW) <15mV IN OUT PP Nominal Switching Frequency 2.25 MHz 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1040 QUAD DC/DC CONVERTER QUICK START PROCEDURE Demonstration Circuit 1040 is easy to set up to evalu- 4. Vary the input voltage from 5.5V to 2.5V, all ate the performance of the LTC3544. For proper four output voltages should be within +/- 2% measurement equipment configuration, set up the tolerance. circuit according to the diagram in Figure 1. 5. Vary the VOUT1 load current from 0 to NOTE: When measuring the input or output voltage 100mA,. Each output voltage should be ripple, care must be taken to avoid a long ground lead within a tolerance of +/- 2%. on the oscilloscope probe. Measure the input or out- 6. Vary the VOUT2 and VOUT3 load currents put voltage ripple by touching the probe tip directly from 0 to 200mA,. Each output voltage should across the VIN or VOUT and GND terminals. See the be within a tolerance of +/- 2%. Measurement Equipment Set-up diagram in Figure 2 7. Vary the VOUT4 load current from 0 to for proper scope probe technique. 300mA. Each output voltage should be within 1. Connect the input power supply to the VIN a tolerance of +/- 2%. and GND terminals. Connect the loads be- 8. To turn either output off, place corresponding tween the matching VOUT and GND terminals. jumper in OFF position. Refer to Figure 1 for the proper measurement equipment setup. Make sure that loads on Warning - If the power for the demo board is carried in outputs VOUT1 through VOUT4 do not exceed long leads, the input voltage at the part could ring, 100mA, 200mA, 200mA and 300mA respec- which could affect the operation of the circuit or even tively. exceed the maximum voltage rating of the IC. To elimi- nate the ringing, insert a small tantalum capacitor (for 2. Apply 5V at VIN and place RUN jumper shunts instance, AVX part TAJW686M010) on the pads be- JP1 through JP4 in the ON positions. tween the input power and return terminals on the bot- 3. Measure all four outputs VOUT1 through tom of the demo board. The (greater) ESR of the tanta- VOUT4 they should read 1.2V, 1.5V, 0.8V, lum will dampen the (possible) ringing voltage due to 1.8V respectively. All output voltages should the use of long input leads. On a normal, typical PCB, be within +/- 2% tolerance. with short traces, the capacitor is not needed. 2