DC125 LTC1538-AUX 1438/LTC1439 LTC1538-AUX/LTC1539 DC125A TPC01 MMBD914L - Datasheet Archive

 

DESIGN-READY SWITCHERS U DESCRIPTIO LTC1538-AUX Constant Frequency, Synchronous, Triple Output DC/DC Converter Demonstration

 

DEMO MANUAL DC125 DC125 DESIGN-READY SWITCHERS U DESCRIPTIO LTC1538-AUX LTC1538-AUX Constant Frequency, Synchronous, Triple Output DC/DC Converter Demonstration circuit board DC125 DC125 is a 200kHz, constantfrequency, triple-output, 2% tolerance power supply using a low noise dual switching regulator controller. A 5V/4% accurate standby internal regulator capable of powering external system wake-up circuitry is also available and active when the switching controllers are shut down. The first two outputs are set for 5V/3A and 3.3V/3A and the third output is a low noise 12V/200mA linear regulator powered from a secondary winding of the 5V output. Refer to the LTC ® 1438/LTC1439 1438/LTC1439 and LTC1538-AUX/LTC1539 LTC1538-AUX/LTC1539 data sheets for other possible configurations. A secondary feedback input to the first controller guarantees 12V load regulation regardless of the load on the primary 5V output. WW U W PERFOR A CE SU ARY The controllers operate at a constant frequency until the output current falls to less than 10% of rated current, thereby providing low sporadic noise operation. This feature minimizes audible or unpredictable radiation. Burst ModeTM operation is invoked below 10% of rated load to maximize efficiency at low currents. The controller can operate at up to 99% duty cycle for very low dropout conditions. The demonstration board operates on an input supply of from 5.2V to 28V, but 12V output power is limited at low input voltages. Gerber files for this circuit board are available. Call the LTC factory. , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a trademark of Linear Technology Corporation. (continued on page 3) Operating temperature range 0°C to 50°C. PARAMETER Input Voltage Range Outputs CONDITIONS Input Voltage Limited by External MOSFET Drive and Breakdown Requirements Output Voltage: Controller 1 (J1 to J6) Output Voltage: Controller 2 (J5 to J8) Max Output Current (Continuous): 5V Output Max Output Current (Continuous): 3.3V Output Typical Output Ripple at 10MHz BW (Continuous): IO = 1A, 3.3V and 5V Outputs; VIN = 10V Frequency Line Regulation Load Regulation LIMITS 5.2V to 28V 5V ± 0.10V 3.3V ± 0.08V 3A 3A 20mVP-P COSC = 56pF, PLLIN Open VIN = 6V to 20V: 3.3V/5V Outputs IO = 0.01A to 3A: 3.3V/5V Outputs 200kHz ±5mV ­ 30mV U U W TYPICAL PERFORMANCE CHARACTERISTICS AND BOARD PHOTOS Efficiency vs Load Current Front Back 100 VIN = 10V CH1 = 5V EFFICIENCY (%) 90 80 70 60 50 0.001 5V MEASURED WITH 3.3V OFF 3.3V MEASURED WITH 5V OFF 0.1 0.01 1.0 OUTPUT CURRENT (A) 10 DC125A DC125A · TPC01 TPC01 1 28 TGL1 25 BG1 24 INTVCC /5V 23 PGND 22 BG2 21 EXTVCC 20 SW2 19 TGL2 2 3 4 5 6 7 8 9 SENSE + 1 SENSE ­ 1 VPROG ITH1 COSC SGND SFB1 ITH2 10 16 AUXFB 15 AUXDR SENSE + 2 13 RUN/SS2 14 C8, 220pF R14 221k SW1B C11 0.1µF C12, 56pF R15 10k R12 1k C9 R5 220pF 392k C20, 1000pF D5 MMBD914L MMBD914L C2 1000pF C7, 470pF R13 10k C15 1000pF C14 0.1µF C3, 56pF, 5% C13, 1000pF R2 100 14 13 12 11 10 9 8 7 6 5 4 3 2 1 SW1C INTVCC BG1 VIN SW1 TGL1 24 25 26 27 28 SW1A 23 ITH1 PGND LTC1538-AUX LTC1538-AUX 22 COSC BG2 21 SGND EXTVCC 20 SW2 SFB1 19 TGL2 ITH2 18 VOSENSE2 BOOST 2 17 SENSE ­ 2 AUXON 16 SENSE + 2 AUXFB 15 RUN/SS2 AUXDR VPROG1 SENSE ­ 1 SENSE + 1 RUN/SS1 BOOST1 M2 M3 M1B M1A L1 R6 0.033 D3 MBRS140 MBRS140 D1 MBRS140 MBRS140 T1 1: 1.8 C16, C19 100µF, 10V R10 0.033 D6 MBRS1100 MBRS1100 C5 10µF 25V C21 C22 22µF 35V C28 C29 100µF 10V C4 3.3µF 35V R9 47k + + + Q1 2N2907 2N2907 R4 90.9k R3 1M VOUT2 3.3V 3A GND VOUT1 5V 3A VOUT3 12V VIN 5.2V TO 28V DM125 DM125 · SCHEMATIC VIN 5.2V TO 28V: SWITCHING FREQUENCY: 200kHz L1: 10µH, SUMIDA CDRH125-100MC CDRH125-100MC T1: DALE LPE6562-A262 LPE6562-A262 GAPPED E-CORE OR BH ELECTRONICS #501-0657 GAPPED TOROID M1: SILICONIX Si4936DY Si4936DY M2, M3: SILICONIX Si4412DY Si4412DY ALL INPUT AND OUTPUT CAPACITORS ARE AVX-TPS SERIES C27, 0.1µF D4 CMDSH-3 C24, 4.7µF, 16V 22µF 35V + C25, C26 D2 CMDSH-3 C6 0.1µF 5V STANDBY R16 3.3M C23, 0.1µF R1 10 Figure 1. LTC1538-AUX LTC1538-AUX Fixed 5V/3.3V and 12V Linear, High Efficiency Triple Regulator D7 MMBD914L MMBD914L R8 10 R7 10 C10, 1000pF C18, 22pF R11 100 17 AUXON SENSE ­ 2 12 G PACKAGE 28-LEAD 28-LEAD PLASTIC SSOP 18 BOOST 2 VOSENSE2 11 LTC1538CG-AUX LTC1538CG-AUX U W 26 VIN 27 SW1 1 + BOOST 1 PACKAGE A D SCHE ATIC DIAGRA S W RUN/SS1 + 2 + TOP VIEW DEMO MANUAL DC125 DC125 DESIGN-READY SWITCHERS DEMO MANUAL DC125 DC125 DESIGN-READY SWITCHERS WW U W PERFOR A CE SU PARAMETER Supply Current Shutdown Current 5V Standby Voltage V12V ARY (continued from page 1) CONDITIONS VIN = 15V, 5V/3.3V On, 12V Off, EXTVCC = VOUT1 VIN =15V, RUN/SS1 and RUN/SS2 = 0V VIN =15V, RUN/SS1 and RUN/SS2 = 0V SW2B in the ON Position; ILOAD = 0.1mA to 100mA LIMITS 320µA 70µA 5V ± 0.2V 12V ± 5% PARTS LIST REFERENCE DESIGNATOR QUANTITY C1 1 C2, C10, C13, C15, C20 5 C3 1 C4 1 C5 1 C6, C11, C14, C23, C27 5 C7 1 C8, C9 2 C12 1 C16, C19, C28, C29 4 C17 - Option 1 C18 1 C21, C22, C25, C26 4 C24 1 D1, D3 2 D2, D4 2 D5, D7 2 D6 1 J1 to J8 8 J9 1 L1 1 M1 1 M2, M3 2 Q1 1 R1, R7, R8 3 R2, R11 2 R3 1 R4 1 R5 1 R6, R10 2 R9 1 R12 1 R13, R15 2 R14 1 R16 1 SW1 1 T1 - Gapped E-Core 1 T1 - Gapped SMT Toroid 1 U1 1 PART NUMBER 6SL150M 6SL150M 08055A102KAT1A 08055A102KAT1A 08055A560JAT1A 08055A560JAT1A TAJC335M035R TAJC335M035R TAJC106M025R TAJC106M025R 08055C104MAT1A 08055C104MAT1A 08055A471KAT1A 08055A471KAT1A 08055A221KAT1A 08055A221KAT1A 08055A560KAT1A 08055A560KAT1A TPSD107M010R0080 TPSD107M010R0080 10SL100M 10SL100M 08055A220KAT1A 08055A220KAT1A TPSE226M035R0300 TPSE226M035R0300 TAJB475M016R TAJB475M016R MBRS140T3 MBRS140T3 CMDSH-3TR MMBD914LT1 MMBD914LT1 MBRS1100T3 MBRS1100T3 1502-2 38015-06G1 38015-06G1 CDRH125-100MC CDRH125-100MC Si4936DY Si4936DY Si4412DY Si4412DY MMBT2907ALT1 MMBT2907ALT1 CR21-100J-T CR21-100J-T CR21-101J-T CR21-101J-T CR21-1004F-T CR21-1004F-T CR21-9092F-T CR21-9092F-T CR21-3923F-T CR21-3923F-T LR2010-01-R033-F LR2010-01-R033-F CR21-473J-T CR21-473J-T CR21-102J-T CR21-102J-T CR21-103J-T CR21-103J-T CR21-2213F-T CR21-2213F-T CR21-105J-T CR21-105J-T 90HBW03S 90HBW03S LPE-6562-A262 LPE-6562-A262; Gapped E-Core 501-0657; Gapped SMT Toroid LTC1538-AUXCG28 LTC1538-AUXCG28 DESCRIPTION 150µF 6.3V 20% OS-CON Capacitor 1000pF 50V 20% NPO Capacitor 56pF 50V 5% NPO Capacitor 3.3µF 35V 20% Tantalum Capacitor 10µF 25V 20% Tantalum Capacitor 0.1µF 50V 20% X7R Capacitor 470pF 50V 10% NPO Capacitor 220pF 50V 10% NPO Capacitor 56pF 50V 10% NPO Capacitor 100µF 10V 20% Tantalum Capacitor 100µF 10V 20% OS-CON Capacitor Option 22pF 50V 10% NPO Capacitor 22µF 35V 20% Tantalum Capacitor 4.7µF 16V 20% Tantalum Capacitor 40V 1A Schottky Diode 30V 0.1A Schottky Diode 100V General Diode 100V 1A Schottky Diode 2-Turrent Terminal 6-Pin 1-Row 0.100cc Connector 10µH 4A 20% SMT Inductor Dual N-Channel MOSFET Transistor N-Channel MOSFET Transistor PNP Transistor 10 1/10W 1/10W 5% Chip Resistor 100 1/10W 1/10W 5% Chip Resistor 1M 1/10W 1/10W 1% Chip Resistor 90.9k 1/10W 1/10W 1% Chip Resistor 392k 1/10W 1/10W 1% Chip Resistor 0.033 1/2W 1% Chip Resistor 47k 1/10W 1/10W 5% Chip Resistor 1k 1/10W 1/10W 5% Chip Resistor 10k 1/10W 1/10W 5% Chip Resistor 221k 1/10W 1/10W 1% Chip Resistor 1M 1/10W 1/10W 5% Chip Resistor 3-Position SPST SMT Switch 10µH 3A 1:1.8 Transformer 10µH 3A 1:1.8 Transformer LTC1538-AUX LTC1538-AUX IC VENDOR Sanyo AVX AVX AVX AVX AVX AVX AVX AVX AVX Sanyo AVX AVX AVX Motorola Central Motorola Motorola Keystone Comm Con Sumida Siliconix Siliconix Motorola AVX AVX AVX AVX AVX IRC AVX AVX AVX AVX AVX Grayhill Dale BH Electronics LTC 3 DEMO MANUAL DC125 DC125 DESIGN-READY SWITCHERS U W U MANUFACTURER TELEPHONE DIRECTORY MANUFACTURER AVX Ceramic Capacitors Resistors BH Electronics Central Comm Con Dale Grayhill IR IRC Keystone LTC Motorola Siliconix (Temic) Sanyo Sumida USA (803) 448-9411 (803) 946-0362 (803) 946 0524 (612) 894-9590 (516) 435-1110 (818) 301-4200 (605) 665-9301 (708) 354-1040 (310) 322-3331 (512) 992-7900 (718) 956-8900 (408) 432-1900 (602) 244-5768 (408) 970-5700 (619) 661-6835 (708) 956-0666 EUROPE (0252) 336868 JAPAN HONG KONG 3633303 SINGAPORE 49 8161 43963 TAIWAN/KOREA 822 268 9795 49 9287 71434 65 747 2767 44 883 713 215 (852) 803 7380 49 89 921030 49 07131 67-0 (852) 480 8333 (852) 23-789-789 0720-70-1005 03-3607-5111 8806688 29 633 88 02-726-2177-9 QUICK START GUIDE The demonstration board is easily set up to evaluate the performance of the LTC1538-AUX LTC1538-AUX. Please follow the procedure outlined below for proper operation. · Refer to Figure 2 for board orientation and proper measurement equipment setup. · Set the three DIP switches, (SW1a, SW1b and SW1c) to the left position (switches closed). · Connect the desired loads between VOUT1, VOUT2, V12V and their closest PGND terminals on the board. The loads can be up to 3A for VOUT1, 3A for VOUT2 and up to 200mA for V12V. Soldered wires should be used when the load current exceeds 1A in order to achieve optimum performance. · Connect the input power supply to the VIN and PGND terminals on the top, center of the board. Do NOT increase VIN over 28V or the MOSFETs MAY BE DAMAGED. · Switch on the desired channel(s) by moving SW1a, SW1b and SW1c to the open position (12VON 12VON, 3.3VRUN and 5VRUN) allowing the soft start capacitors to ramp positive. · Measure VOUT1 and VOUT2 to verify output voltages of 5V ±0.1V and 3.3V ±0.08V, respectively, at load currents of 1A each. · Measure V12V to verify output voltage of 12V ±5% at a load current of 0.1A . U OPERATIO The circuit shown in Figure 1 provides fixed voltages of 5V, 3.3V and 12V. It provides 5V and 3.3V output voltages at currents up to 3A. The 12V output can deliver up to several hundred milliamps limited only by the thermal dissipation available to Q1 in DC125 DC125. Figure 2 illustrates the correct measurement setup in order to verify the typical numbers found in the Performance Summary table. Small spring clip leads are very convenient for small-signal bench 4 testing but should not be used at the current and impedance levels associated with this switching regulator. Soldered wire connections are required to properly ascertain the performance of this demonstration PC board. The LTC1538-AUX LTC1538-AUX switching regulator performs high efficiency DC-to-DC voltage conversion while maintaining constant frequency over a wide range of load current, using a current mode architecture. The oscillator fre- DEMO MANUAL DC125 DC125 DESIGN-READY SWITCHERS U OPERATIO A 12V LOAD V12V A V voltage decreases, the duty cycle increases, meaning that there is less off time for the secondary winding to operate. Ultimately, it will not be able to supply the average current required by the 12V auxiliary regulator. The demonstration board will provide 12V at its 200mA rated output current with the input supply at 7V or greater. + VIN ­ V OFF-ON J3 J4 J2 J7 SW1 J5 J8 J9 J1 J6 DEMO CIRCUIT DC125A DC125A VOUT2 V VOUT1 V A A 3.3V LOAD 5V LOAD DM125 DM125 · F02 Figure 2. Proper Measurement Setup quency is set by the selection of the external capacitor on Pin 7. The demonstration board is set up with a 56pF capacitor to run at 200kHz. High efficiency is made possible by using a new Burst Mode operation architecture employing pulse skipping at low output currents. At very light loads and with an input-to-output voltage differential of 2V or less, the device will go into a voltage mode of operation in order to recharge the boost capacitors periodically. The first controller can be forced into continuous operation by tying the SFB1 input pin to signal ground. The demonstration board is shipped in a standard configuration of 5V/3.3V/12V. The secondary winding of transformer T1 develops a voltage on capacitor C4. This voltage is divided down by the resistive divider comprising R3 and R4. This divided down voltage is compared against the internal 1.19V reference voltage at the SFB1 pin and forces the first regulator's output stage to be activated for as long as required to support the 12V load. The inductor current will even be allowed to reverse, in order to provide enough flyback period to charge the secondary winding's filter capacitor. An internal attenuator set for a 12V output is connected in series with the AUXFB pin when the voltage applied to the AUXDR pin is greater than 9.5V. The secondary winding on the transformer T1, in conjunction with the feedback control loop, produces a regulated flyback voltage of 14V, provided that the duty cycle of the 5V regulator is not too high. Current flows in the secondary winding only during the off time of the first controller's top MOSFET. As the If fully loaded 12V operation is required all the way down to the dropout point of the 5V regulator, controller 1 could be set to 3.3V, controller 2 could be set to 5V and a transformer with a higher turns ratio could be used. Consult the factory for assistance or refer to the LTC1538-AUX/ LTC1538-AUX/ LTC1539 LTC1539 data sheet for a typical application circuit. The auxiliary regulator drive output can typically sink 15mA, providing enough external PNP base drive for a 500mA regulator. Power dissipation must be considered for the PNP output device as well as for the IC. A circuit adding a low-sat NPN can be configured for currents in the 0.5A to 5A range if a higher current linear regulator is desired. See the LTC1538-AUX/LTC1539 LTC1538-AUX/LTC1539 data sheet for additional information. Efficiency measurement depends on the operating conditions of all three regulators and must be performed with care. Efficiency figures should ideally be taken with only the minimum required circuitry operating on an individual regulator. Since there is much common circuitry operating when more than one regulator is running, overall efficiency numbers will actually increase when the two switching regulators are active. The increase is not significant at high output currents but can become very significant at low output currents, when the IC supply current becomes an appreciable part of the total input supply current. Refer to the LTC1538-AUX/LTC1539 LTC1538-AUX/LTC1539 data sheet for further information on the internal operation and functionality descriptions of the IC. Physical Design The demonstration board is manufactured using a typical 4-layer/1oz copper PC board. The board is available with a choice of two different types of inductors. The first, pictured in the front page photo, is a Dale LPE6562-A262 LPE6562-A262 gapped E-core. The second is a BH Electronics 501-0657 5 DEMO MANUAL DC125 DC125 DESIGN-READY SWITCHERS U OPERATIO gapped toroid. The turns ratio is the same for both transformers at 1:1.8, providing the proper unregulated 14V output for the auxiliary internal linear regulator. The Dale inductor supplies slightly more output current prior to saturating than the BH unit, but the toroid will be offered in a significantly smaller package than shipped with the demonstration board (consult the manufacturer). The Dale and BH transformers shipped with the demo board are released part numbers from the manufacturers. PC Board Layout Hints Switching power supply printed circuit layouts are certainly among the most difficult analog circuits to design. The following suggestions will help to get a reasonably close solution on the first try. The output circuits, including the external switching MOSFETs, inductor, secondary windings, sense resistor, input capacitors and output capacitors all have very large voltage and/or current levels associated with them. These components and the radiated fields (electrostatic and/or electromagnetic) must be kept away from the very sensitive control circuitry and loop compensation components required for a current mode switching regulator. The electrostatic or capacitive coupling problems can be reduced by increasing the distance from the radiator, typically a very large or very fast moving voltage signal. The signal points that cause problems generally include the "switch" node, any secondary flyback winding voltage and any nodes that also move with these nodes. The switch, MOSFET gate and boost nodes move between VIN and PGND each cycle with less than a 100ns transition time. The secondary flyback winding output has an AC signal component of ­ VIN times the turns ratio of the transformer, and also has a similar