advertisement SOT-23 Switching Regulator with Integrated 1A Switch Delivers High Current Outputs in a Small Footprint – Design Note 232 Albert Wu 5V Local Supply Figure 1 shows a typical 3.3V to 5V boost converter using the LT1930. The circuit can provide an impressive output current of 480mA while occupying less than 0.3" by 0.35" of board area (less than 0.105 in2). The efficiency, shown in Figure 2, remains above 83% over a wide load current range of 60mA to 450mA, reaching 86% at 200mA. The maximum output voltage ripple of this circuit is 40mVP-P, which corresponds to less than 1% of the nominal 5V output. Figure 3 is an oscillograph of the transient response. The lower waveform depicts a load step from 200mA to 300mA, the middle waveform shows the inductor current and the upper waveform shows the output voltage. The output voltage remains within 1% of the nominal value during the transient steps and displays a nice damped response with little ringing. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. 06/00/232_conv L1 5.6μH VIN 3.3V C1 4.7μF D1 5 1 VIN SW VOUT 5V 480mA R1 40.2k LT1930 OFF ON 4 SHDN FB C2 10μF 3 R2 13.3k GND 2 C1: TAIYO-YUDEN X5R JMK212BJ475MG www.t-yuden.com C2: TAIYO-YUDEN X5R JMK316BJ106ML D1: ON SEMICONDUCTOR MBR0520 www.onsemi.com L1: SUMIDA CR43-5R6 www.sumida.com DN232 F01 Figure 1. 3.3V to 5V Boost Converter 90 VIN = 3.3V 85 80 EFFICIENCY (%) Linear Technology’s LT®1930 is the industry’s highest power SOT-23 switching regulator. The device contains an internal 1A, 36V switch and is pin compatible with both the low power LT1613 and the micropower LT1615. The LT1930 provides a simple upgrade path for users of these parts who need more power for new designs. In addition to portable applications requiring higher output currents, the device also fits well in nonbattery-operated equipment. Multiple output power supplies can now use a separate regulator for each output voltage, replacing cumbersome quasi-regulated approaches using a single regulator and custom transformers. The LT1930 utilizes a constant frequency, internally compensated, current mode PWM architecture that results in low, predictable output noise that is easy to filter. Its 1.2MHz switching frequency allows the use of tiny, low cost capacitors and low profile inductors. With an input voltage range of 2.6V to 16V, the LT1930 is a good fit for a variety of applications. VIN = 2.6V 75 70 65 60 55 50 0 100 200 400 300 LOAD CURRENT (mA) 500 DN232 F02 Figure 2. 3.3V to 5V Boost Converter Efficiency VOUT 0.1V/DIV AC COUPLED IL1 0.5A/DIV AC COUPLED LOAD 300mA CURRENT 200mA 20μs/DIV DN232 F03 Figure 3. 3.3V to 5V Boost Converter Transient Response 12V Local Supply Another typical application is a 5V to 12V boost converter as shown in Figure 4. This circuit can provide 300mA of output current and achieves efficiencies of up to 87% as shown in Figure 5. The maximum output voltage ripple of this circuit is 60mVP-P, which corresponds to 0.05% of the nominal 12V output. As seen in Figure 6, the output voltage remains within 1% of the nominal value during a 50mA load step. L1 10μH VIN 5V D1 5 VIN C1 2.2μF SW R1 115k LT1930 4 OFF ON VOUT 12V 300mA 1 SHDN FB ±15V Dual Output Converter with Output Disconnect A ±15V dual output converter using the LT1930 is shown in Figure 7. Both outputs are developed using charge pumps, so both are disconnected from the input when the LT1930 is turned off. Since the supplies are generated in the same manner, this circuit features excellent cross regulation. For a 5× difference in output currents, the positive and negative output voltages differ less than 1%; for a 10× difference, they differ less than 2%. Both outputs of this circuit can each supply up to 70mA of current. The efficiency plot for this circuit is shown in Figure 8. C2 4.7μF 3 2 C1: TAIYO-YUDEN X5R LMK212BJ225MG (408) 573-4150 C2: TAIYO-YUDEN X5R EMK316BJ475ML D1: ON SEMICONDUCTOR MBR0520 (800) 282-9855 L1: SUMIDA CR43-100 (874) 956-0666 DN232 F04 C4 1μF L1 3.3μH VIN 5V R2 13.3k GND 5 OFF ON 15V 70mA 1 C5 1μF SW VIN C1 2.2μF D1 R1 147k LT1930 4 D2 SHDN FB C2 2.2μF 3 R2 13.3k GND 2 Figure 4. 5V to 12V Boost Converter 90 VIN = 5V 85 DN232 F07 –15V 70mA VIN = 3.3V 80 EFFICIENCY (%) C6 2.2μF C1: TAIYO-YUDEN X5R LMK212BJ225MG D3 D4 C2, C3: TAIYO-YUDEN X5R EMK316BJ225ML C4, C5: TAIYO-YUDEN X5R TMK316BJ105ML (408) 573-4150 D1 TO D4: ON SEMICONDUCTOR MBR0520 (800) 282-9855 L1: SUMIDA CR43-3R3 (874) 956-0666 Figure 7. ±15V Dual Output Converter with Output Disconnect 75 70 65 85 60 VIN = 5V 80 55 0 100 200 EFFICIENCY (%) 75 50 300 LOAD CURRENT (mA) DN232 F05 Figure 5. 5V to 12V Boost Converter Efficiency 70 65 60 55 50 VOUT 0.2V/DIV AC COUPLED 0 20 40 60 80 LOAD CURRENT (mA) DN232 F08 IL1 0.5A/DIV AC COUPLED Figure 8. ±15V Dual Output Converter Efficiency LOAD 250mA CURRENT 200mA 20μs/DIV DN232 F06 Figure 6. 5V to 12V Boost Converter Transient Response Data Sheet Download www.linear.com Linear Technology Corporation For applications help, call (408) 432-1900 dn232f_conv LT/TP 0600 340K • PRINTED IN THE USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2000