DC664A Analog Devices

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 664 2-PHASE DUAL STEP-DOWN CONVERTER WITH OUTPUT TRACKING LTC3737EUF DESCRIPTION Demonstration circuit 664 is a high efficiency 2-phase ternally synchronized from 250KHz to 850KHz. The dual step-down DC/DC converter with 2.75V to 9.8V frequency can also be selected with PLLLPF pin. Ty- input range. It has two outputs: 2.5V/2.5A and ing PLLLPF pin to GND selects 300KHz operation 1.8V/3A. The demo board features the constant fre- tying PLLLPF pin to VIN selects 750KHz operation. quency current mode LTC 3737EUF controller. The The demo board has tracking function, allowing V OUT2 MOSFET V sensing eliminates the need for sense DS to track V during start-up. OUT1 resistors and improves efficiency. Out of phase op- Design files for this circuit board are available. Call eration significantly reduces input ripple current and the LTC factory. noise as well as the input capacitor size. LTC is a trademark of Linear Technology Corporation Switching frequency is internally set at 550KHz. For noise sensitive applications, the converter can be ex- Table 1. Performance Summary (T = 25C) A PARAMETER CONDITION VALUE Input Voltage Range 2.75V to 9.8V V V = 2.75V to 9.8V, I = 0A to 2.5A, 2.5V 3% OUT1 IN OUT1 I = 0A to 3A OUT2 V V = 2.75V to 9.8V, I = 0A to 2.5A, 1.8V 3% OUT2 IN OUT1 I = 0A to 3A OUT2 Typical Output Ripple V V = 3.3V, I = 2.5A (20MHz BW) 14mV OUT1 IN OUT1 PP Typical Output Ripple V V = 3.3V, I = 3A (20MHz BW) 19mV OUT2 IN OUT2 PP Typical Switching Frequency PLLLPF Pin Floating 550kHz QUICK START PROCEDURE Demonstration circuit 664 is easy to set up to evalu- 1. With power off, connect the input power supply to ate the performance of LTC3737. Refer to Figure 1 for +Vin (2.75V-9.8V) and GND (input return). proper measurement equipment setup and follow the 2. Connect the 2.5V load (Load 1 in Figure 1) between procedure below: Vout1 and GND connect the 1.8V load (Load 2 in NOTE: When measuring the input or output voltage Figure 1) between Vout2 and GND. (Initial loads: ripple, care must be taken to avoid a long ground lead 0A.) on the oscilloscope probe. Measure the input or out- 3. Connect the DVMs to the input and outputs. put voltage ripple by touching the probe tip directly 4. Turn on the input power supply and check for the across the Vin or Vout and GND terminals. See Figure proper output voltages. Vout1 should be 2.5V+/- 2 for proper scope probe technique. 3%. Vout2 should be 1.8V+/-3%. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 664 2-PHASE DUAL STEP-DOWN CONVERTER WITH OUTPUT TRACKING 5. Once the proper output voltages are established, serve the output voltage regulation, ripple voltage adjust the loads within the operating range and ob- and other parameters. Figure 1. Proper Measurement Equipment Setup 2