QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1389A 1389A DEMO CIRCUIT QUICK START GUIDE LTC3521EUF Synchronous 1A Buck-Boost DC/DC Converter and Dual 600mA Buck DC/DC Converters DESCRIPTION Demonstration circuit 1389A is high efficiency triple output DC/DC power supply featuring the LTC3521. The IC includes a 4-switch synchronous Buck-Boost DC/DC converter with 1A switch ratings and two synchronous 600mA Buck converters. The board will accept an input voltage between 2.4V and 5V, and provide fixed output voltages of 3.3V @800mA for the Buck-Boost converter and 1.2V & 1.8V @600mA for the Buck converters. The board includes jumpers for shutdown for each converter, one jumper for PWM or BURST operation and terminals to monitor each converter’s Power Good output signal. Other features are; 1µA shutdown current, integrated soft start, thermal and over current protection, under voltage lockout, 100% duty cycle for the Buck converter and a 1MHz switching frequency that allows small L and C components to be used. With BURST mode selected, the buck converters operate in BURST mode at low load current and automatically switch to PWM mode at higher loads. The Buck-Boost converter will also operate in burst mode but the available load current is reduced considerably, to approximately 50mA. No load BURST mode quiescent current is approximately 50µA. When all three converters are shutdown, the quiescent current drops to less than 1µA. The Power Good output terminals pull low if the output voltage is 8% or more below the regulation voltage. The LTC3521 datasheet gives a complete description of the part, operation and application information. The datasheet must be read in conjunction with this quick start guide. Design files for this circuit board are available. Call the LTC factory. , LTC and LT are registered trademarks of Linear Technology Corporation. ThinSOT and PowerPath are trademarks of Linear Technology Corporation. Performance Summary ( TA = 25oC ) PARAMETER Input Voltage Range Buck-Boost Output Voltage (Vout 1) Buck Output Voltage (Vout 2) Buck Output Voltage (Vout 3) Maximum Output Current (Buck-Boost) Maximum Output Current (Buck) Input Supply Current Input Supply Current (no load) Input Supply Current (no load) CONDITION Vin = 2.4V, Vout Load = 100mA Vin = 2.4V, Vout Load = 100mA Vin = 2.4V, Vout Load = 100mA Vin = 2.4V, PWM mode Vin = 2.4V All Converters Shutdown, Vin = 2.4V All Converters Enabled, BURST Mode, Vin = 2.4V, No Load All Converters Enabled, PWM Mode, Vin = 2.4V, No Load VALUE 2.4V to 5V 3.3V +/- 2.5% 1.2V +/- 2.5% 1.8V +/- 2.5% 800mA 600mA <1µA 50µA, typ. 8.5mA, typ. Table 1. Circuit Specifications QUICK START PROCEDURE This Demonstration circuit 1389A can be evaluated using the setup shown in Figure 1. 1. Place all Shutdown jumpers in the ON position and the MODE jumper to the PWM position. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1389A 2. With AC power off, connect the input power supply to Vin and GND. current is limited to approximately 50mA if the Mode jumper is set for BURST. 3. Connect voltmeters to Vin and ground terminals and each Vout and Ground terminals. 8. 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 Figure 2 for proper scope probe technique. 4. With the input voltage turned down, switch on the input power supply and raise the input voltage to 1.8V. 5. Verify that each output voltage meets the values as shown in Table 1. 9. The Power Good terminals can be monitored with a voltmeter or an oscilloscope. The Power Good outputs pull low if the output voltage is 8% or more below the regulation voltage, otherwise they are pulled up to their respective output voltage through a 1MΩ pull-up resistor. 6. Increase the input voltage to 2.5V and connect suitable load resistors between each output and ground. 7. Verify each output voltage. If an output is low, temporarily disconnect the load to make sure that the load current is not set too high. Also, monitor the input voltage at the board terminals to verify that the input voltage has not dropped due to the increased input current. Note: The Buck-Boost converter output Shutdown Power Supply 10. To measure no load input current, connect a mA/µA meter in series with the input supply, adjust for 2.4V and read meter. Both BURST and PWM quiescent current can be verified by moving JP1 to the appropriate position. Power Mode Good Outputs + + RL2 Vout2 + RL2 Vout3 + - RL1 Vout1 Figure 1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Voltage Ripple 2 PGOOD3 PGOOD2 PGOOD1 GND VOUT1 3.3V / 1A GND E11 E10 E9 E4 E3 E2 VOUT1 CIN1 47uF 10V PGOOD3 PGOOD2 PGOOD1 C8 0.1uF + OFF ON OFF ON OFF ON JP4 SHDN3 JP3 3 2 1 3 2 SHDN2 1 JP2 3 2 SHDN1 1 C3 22uF 6.3V 1206 R5 221K 1% R4 1.00M 1% 8 C10 (Opt) C9 (Opt) 16 14 2 3 4.7uH CDRH5D16NP-4R7NC Sumida PGOOD3 PGOOD2 4 9 1 10 CIN4 4.7uF 10V 15 R3 1M R2 1M PGOOD1 CIN3 4.7uF 10V 1M VOUT3 L1 VOUT2 VOUT1 R1 CIN2 4.7uF 10V F B1 V O UT1 SW1B SW1A P G O O D3 P G O O D2 P G O O D1 SH DN 3 SH DN 2 SH DN 1 GND 25 5 VIN GND 6 11 PVIN1 21 PGND1A 22 PVIN2 PGND1B 12 E1 F B3 SW3 F B2 SW2 23 17 24 20 7 CDRH2D18/HP-3R3NC Sumida L3 3.3uH CDRH2D18/HP-3R3NC Sumida L2 3.3uH U1 LTC3521EUF P WM PGND2 18 VIN 2.4V - 5V C5 10uF 6.3V 0805 C2 10uF 6.3V 0805 VIN JP1 MODE C4 22pF VOUT3 C1 22pF VOUT2 3 2 1 R9 100K 1% R8 102K 1% R7 68.1K 1% R6 137K 1% BURST PWM C7 0.1uF C6 0.1uF E8 E7 E6 E5 GND VOUT3 1.2V / 600mA GND VOUT2 1.8V / 600mA QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1389A 3