QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 970A HIGH EFFICIENCY, 500MA BUCK PLUS 300MA VLDO REGULATOR LTC3541EDD/LTC3541EDD-1 DESCRIPTION DC970A-A/B featuring the LTC3541/LTC3541-1 pro- lower output ripple voltage at light load currents than vides a high efficiency, 500mA synchronous buck in Burst Mode. In either mode, the DC970A can pro- plus 300mA VLDO regulator. The DC970A has an in- vide up to 95% efficiency and consumes less than put voltage range of 3.0V to 5.5V. The jumper select- 3uA in shutdown. The LTC3541 comes in a small 10- able 2.5V/1.8V output is capable of delivering up to Pin DFN package, which has an exposed pad on the 500mA of output current the jumper selectable bottom-side of the IC for good thermal performance. 0.8V/1.2V/1.5V/1.8V output is capable of delivering These features make the DC970 demo board an ideal up to 300mA of current. The synchronous buck con- reference circuit for battery-powered, hand-held ap- verter provides a high efficiency output, typically 90% plications. while switching at 2.25MHz, allowing the use of small Design files for this circuit board are available. Call surface mount inductor and capacitors. In Burst the LTC factory. Mode operation, the LTC3541 /LTC3541-1s low qui- LTC is a trademark of Linear Technology Corporation escent current results in high efficiency at light load currents. In Pulse Skip mode, the DC970A provides Table 1. Performance Summary (T = 25C) A PARAMETER CONDITION VALUE DC970A-A Buck output Vout1 rise ahead of LDO Vout2 IC: LTC3541 DC970A-B LDO output Vout2 rise ahead of Buck Vout1 IC: LTC3541-1 V V + 1.4V Input Voltage range 3V-5.5V IN out2 Output Voltage V V = 3V to 5.5V, I = 0A to 500mA 1.8V / 2.5V 2% OUT1 IN OUT1 Typical Output Ripple V V = 4.5V, I = 500mA (20MHz BW) 20mV OUT1 IN OUT1 PP 0.8V 2% 1.2V 2% Output Voltage V V = 3V to 5.5V, I = 0A to 300mA OUT2 IN OUT2 1.5V 2% 1.8V 2% Typical Output Ripple V V = 4.5V, I = 300mA (20MHz BW) 10mV OUT2 IN OUT2 PP Nominal Switching Frequency 2.25MHz 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 970A HIGH EFFICIENCY, 500MA BUCK PLUS 300MA VLDO REGULATOR QUICK START PROCEDURE Demonstration circuit 970A is easy to set up to evalu- 4. Set JP9 in V position. In some rare applications, OUT1 ate the performance of the LTC3541. Refer to Figure 1 if external input for VLDO is desired, set JP9 to for proper measurement equipment setup and follow LVIN EXT. Check datasheet for more detailed us- the procedure below. age of external input for VLDO. Note: When measuring the input or output voltage 5. Apply 3.3V at Vin. Measure both Vouts they ripple, care must be taken to avoid a long ground lead should read 0V. The supply current will be less on the oscilloscope probe. Measure the input or out- than 3uA in shutdown condition. put voltage ripple by touching the probe tip directly 6. Turn on Vout1 and Vout2 by changing jumpers JP5 across the Vin or Vout and GND terminals. See Figure and JP7 from the OFF position(s) to the ON posi- 2 for proper scope probe technique. tion(s). Vary the input voltage from 3V to 5.5V and 1. Connect the input power supply to the Vin and check output voltage. Both output voltages should GND terminals on the left-side of the board. Do be regulating. The regulated error should be less not hot-plug Vin or increase Vin over the rated than 2% of rated voltage. In non load burst mode maximum supply voltage of 5.5V. Connect the with both Buck (Vout1) and VLDO (Vout2) enabled loads between the Vout and GND terminals on the the input current should be less than 70uA. right-side of the board. Refer to Figure 1 for the 7. Set the load current of outputs between 25% to proper measurement equipment setup. 100% load range, and measure both output ripple 2. Minimum operating V voltage required for VLDO voltages they should measure less than 20mV IN regulator and linear regulator regulation is: each. Please note, the maximum load on Vout1 is 500mA minus load on Vout2. The switching fre- V Vout2 + 1.4V and V 3.0V. IN IN quencies should be between 1.8MHz and 2.7MHz. 3. Before proceeding to operation, insert jumpers JP5 8. Jumper default position: (total of 6 jumpers and JP7 into the OFF positions, jumper JP1-JP4 needed) into the Vout2 voltage position of choice (0.8V, 1.2V, 1.5V, and 1.8V), jumper JP8 into the Vout1 JP9 JP8 JP7 JP6 JP5 JP1- voltage position of choice (1.8V and 2.5V) and JP4 jumper JP6 into the desired mode of operation: Vout1 1.8V ON BURST ON 1.2V Pulse Skip or Burst Mode. 2