QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 611 DUAL, SPREAD-SPECTRUM, LOW NOISE, INDUCTORLESS STEP DOWN DC/DC CONVERTER LTC3252 DESCRIPTION Demonstration circuit 611 is a dual, spread-spectrum, step appropriate layout techniques for the LTC3252 inductorless down charge pump DC/DC converter featuring the DC-DC converter. This power supply circuit is ideally LTC 3252EDE. It produces regulated 1.5V and 1.2V suited for space-constrained battery-powered applications output voltages at up to 250mA of output current each from that require small size and low operating current. 2.7V to 5.5V input. The unique spread spectrum Design files for this circuit board are available. architecture of the LTC3252 provides highly efficient and Call the LTC factory. low noise operation. The circuit has a low external parts LTC is a registered trademark of Linear Technology Corporation. count and requires only five small surface mount capacitors and four tiny surface mount resistors. DC611 demonstrates QUICK START PROCEDURE Demonstration circuit 611 is easy to set up and evaluate the 1. With power off, connect input power source to V and IN performance of the LTC3252. Refer to Figure 1 for proper GND terminals. Input voltage range is limited to measurement equipment setup and follow the procedure between 2.7V and 5.5V for the 1.2V output and below: between 3.21V and 5.5V for the 1.5V output. NOTE: When measuring the input or output voltage ripple, 2. Place selector jumper JP1 in the ON position to enable care must be taken to avoid a long ground lead on the V (1.5V), and jumper JP2 in the ON position to OUT1 oscilloscope probe. Measure the input or output voltage enable V . OUT2 ripple by touching the probe tip directly across the V , IN 3. If desired, loads may be connected from V to GND OUT1 V or V and GND terminals. See Figure 2 for proper OUT1 OUT2 and from V to GND. The following V (min) vs. OUT2 IN scope probe technique. load chart must be followed to ensure correct regulation of V and V : OUT1 OUT2 Table 1. V VS. LOAD CHART IN V (min) vs load IN V (MIN) I I IN OUT1 OUT2 3.5V 250mA 250mA 3.2V 100mA 250mA 3.1V 50mA 250mA 2.9V --- 250mA 2.7V --- 150mA 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 611 DUAL, SPREAD-SPECTRUM, LOW NOISE, INDUCTORLESS STEP DOWN DC/DC CONVERTER NOTE: V is in dropout for V < 3.0V and will cause the V = 1.2V. If there is no output, temporarily disconnect OUT1 IN OUT2 LTC3252 to operate in continuous mode instead of the the load to make sure that the load is not set too high. more efficient burst mode. To monitor the actual 6. Once the proper output voltages are established, adjust performance of V for V <3.1V, V should be OUT2 IN OUT1 the loads up to 250mA and observe the output voltage disabled by placing jumper JP1 in the OFF position. regulation, input and output ripple voltage, efficiency and 4. Turn on the power at the input. other parameters. Remember to follow the V (min) vs. IN load chart for correct regulation of V and V . OUT1 OUT2 NOTE: Make sure that the input voltage does not exceed 5.5V. 5. Check for the proper output voltages. V = 1.5V and OUT1 Figure 1. Proper Measurement Equipment Setup Figure 2. Scope Probe Placement for Measuring Input or Output Ripple 2