datasheet search site
Document overview
- Manufacturer or author: pROVIDED bY www.digicamel.com(free datasheet download site)
- PDF pages: 20
Technical content
Isolated Switching Regulator With Integrated Feedback Data Sheet ADuM3070 Rev. 0 Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 ©2012 Analog Devices, Inc. All rights reserved.
FEATURES
Isolated PWM feedback with built in compensation Primary side transformer driver for up to 2.5 W output power with 5 V input voltage Regulated adjustable output: 3.3 V to 24 V Up to 80% efficiency 200 kHz to 1 MHz adjustable oscillator Soft start function at power-up Pulse-by-pulse overcurrent protection Thermal shutdown
2500 V rms isolation
High common-mode transient immunity: >25 kV/µs 16-lead QSOP package High temperature operation: 105°C
APPLICATIONS
Power supply startup bias and gate drives Isolated sensor interfaces Process controls FUNCTIONAL BLOCK DIAGRAM Figure 1. GENERAL DESCRIPTION The ADuM30701 isolator is a regulated dc-to-dc isolated power supply controller with an internal MOSFET driver. The dc-to- dc controller has an internal isolated PWM feedback from the secondary side based on the iCoupler® chip scale transformer technology and complete loop compensation. This eliminates the need to use an optocoupler for feedback and compensates the loop for stability. The ADuM3070 isolator provides a more stable output voltage and higher efficiency compared to unregulated isolated dc-to-dc power supplies. The fully integrated feedback and loop compensation in a small QSOP package provides a smaller form factor than any discrete solution. The regulated feedback provides a relatively flat efficiency curve over the full output power range. The ADuM3070 enables a dc-to-dc converter with a 3.3 V to 24 V isolated output voltage range from either a 5.0 V or a 3.3 V input voltage, with an output power of up to 2.5 W. 1 Protected by U.S. Patents 5,952,849; 6,873,065; and 7075 329 B2. Other patents are pending. ADuM3070 10437-001 PRIMARY CONVERTER/ DRIVER SECONDARY CONTROLLER INTERNAL FEEDBACK VDD2 OC FB VREG VDD1 VISO VDDA X2X1 GND1 GND2 REG RECT NOTES 1. VDD1 IS THE POWER SUPPLY FOR THE PUSH-PULL TRANSFORMER. 2. VDDA IS THE POWER SUPPLY OF SIDE 1 OF THE ADuM3070.
Rev. 0 | Page 2 of 20 TABLE OF CONTENTS Electrical Characteristics—5 V Primary Input Supply/5 V Electrical Characteristics—3.3 V Primary Input Supply/3.3 V Electrical Characteristics—5 V Primary Input Supply/3.3 V Electrical Characteristics—5 V Primary Input Supply/15 V DIN V VDE V 0884-10 (VDE V 0884-10) Insulation
REVISION HISTORY
5/12—Revision 0: Initial Version
otherwise noted. All typical specifications are at TA = 25°C, VDD1 = VDDA = 5.0 V , VDD2 = VREG = VISO = 5.0 V . Table 1. DC-to-DC Converter Static Specifications 1 VDD1 is the power supply for the push-pull transformer. 2 VDDA is the power supply of Side 1 of the ADuM3070. noted. All typical specifications are at TA = 25°C, VDD1 = VDDA = 3.3 V , VDD2 = VREG = VISO = 3.3 V . Table 2. DC-to-DC Converter Static Specifications 1 VDD1 is the power supply for the push-pull transformer. 2 VDDA is the power supply of Side 1 of the ADuM3070.
typical specifications are at TA = 25°C, VDD1 = VDDA = 5.0 V , VDD2 = VREG = VISO = 3.3 V . Table 3. DC-to-DC Converter Static Specifications 1 VDD1 is the power supply for the push-pull transformer. 2 VDDA is the power supply of Side 1 of the ADuM3070. otherwise noted. All typical specifications are at TA = 25°C, VDD1 = VDDA = 5.0 V, VREG = VISO = 15 V, VDD2 = 5.0 V . Table 4. DC-to-DC Converter Static Specifications 1 VDD1 is the power supply for the push-pull transformer. 2 VDDA is the power supply of Side 1 of the ADuM3070.
Rev. 0 | Page 5 of 20 PACKAGE CHARACTERISTICS Table 5. Parameter Symbol Min Typ Max Unit Test Conditions/Comments RESISTANCE RI-O 1012 Ω Input to Output1 CAPACITANCE CI-O 2.2 pF f = 1 MHz Input to Output1 THERMAL IC Junction-to-Ambient Thermal Resistance2 θJA 76 °C/W Thermal Shutdown Threshold TSSD 150 °C TJ rising Hysteresis TSSD-HYS 20 °C 1 The device is considered a 2-terminal device: Pin 1 to Pin 8 is shorted together, and Pin 9 to Pin 16 is shorted together. 2 The thermocouple is located at the center of the package underside. REGULATORY APPROVALS (PENDING) Table 6. UL CSA VDE Recognized under the UL 1577 Component Recognition Program1 Approved under CSA Component Acceptance Notice #5A Certified according to DIN V VDE V 0884-10 (VDE V 0884-10):2006-122 Single Protection, 2500 V rms Isolation Voltage Basic insulation per CSA 60950-1-03 and IEC 60950-1,
400 V rms (848 V peak) maximum working voltage
Reinforced insulation, 560 V peak File E214100 File 205078 File 2471900-4880-0001 1 In accordance with UL 1577, each ADuM3070 is proof tested by applying an insulation test voltage of ≥3000 V rms for 1 sec (current leakage detection limit = 10 µA). 2 In accordance with DIN V VDE V 0884-10, each ADuM3070 is proof tested by applying an insulation test voltage of ≥1050 V peak for 1 sec (partial discharge detection limit = 5 pC). The asterisk (*) marking branded on the component designates DIN V VDE V 0884-10 approval. INSULATION AND SAFETY RELATED SPECIFICATIONS Table 7. Parameter Symbol Value Unit Test Conditions/Comments Rated Dielectric Insulation Voltage 2500 V rms 1-minute duration Minimum External Air Gap (Clearance) L(I01) >3.8 mm Measured from input terminals to output terminals along the printed circuit board (PCB) seating plane Minimum External Tracking (Creepage) L(I02) >3.1 mm Measured from input terminals to output terminals, shortest distance path along body Minimum Internal Gap (Internal Clearance) 0.017 min mm Distance through insulation Tracking Resistance (Comparative Tracking Index) CTI >400 V DIN IEC 112/VDE 0303 Part 1 Isolation Group II Material Group (DIN VDE 0110, 1/89, Table 1)
the safety data. The asterisk (*) marking on packages denotes DIN V VDE V 0884-10 approval. Figure 2. Thermal Derating Curve, Dependence of Safety Limiting Values on Ambient Temperature, per DIN V VDE V 0884-10
TA = 25°C, unless otherwise noted. 1 All voltages are relative to their respective ground.
2 VDD1 is the power supply for the push-pull transformer, and VDDA is the power
supply of Side 1 of the ADuM3070. Table 11. Maximum Continuous Working Voltage Supporting
1 Refers to the continuous voltage magnitude imposed across the isolation
barrier. See the Insulation Lifetime section for more information.
Figure 3. Pin Configuration See Application Note AN-1109 for specific layout guidelines. Table 12. Pin Function Descriptions 1 X1 Transformer Driver Output 1. 2, 8 GND1 Ground Reference for Primary Side. 3, 11, 12 NC No Connect. Do not connect to this pin. 5, 6 TP Test Point. Do not connect to this pin. 4 X2 Transformer Driver Output 2. 9, 15 GND2 Ground Reference for Secondary Side. frequency of 200 kHz to 1 MHz, as programmed by the resistor value. divider is required even in open-loop mode to provide soft start. Connect a 0.1 µF bypass capacitor from VDD2 to GND2. to regulate the VDD2 output to 5.0 V. BOTH TO GND2 IS RECOMMENDED.
- NC = NO CONNECT. DO NOT CONNECT TO THIS PIN.
- TP = TEST POINT. DO NOT CONNECT TO THIS PIN.
higher power and efficiency. note in Figure 31 about connecting together VREG, VDD2, and VISO. can be connected to the regulator input, VREG (Pin 16), of the part. example, VDD1 = 3.3 V , VISO = 5 V), connect VREG to VISO directly. Figure 31. Single Power Supply Figure 32. Doubling Power Supply Figure 33. Positive and Unregulated Negative Supply
2 GND1
8 GND1
16 VREG
15 GND2
14 VDD2
9 GND
FOR VISO = 3.3V OR 5V CONNECT VREG, VDD2, AND VISO. FOR VISO = 15V OR LESS, VREG CAN CONNECT TO VISO.
7 VDDA
9 GND2
Rev. 0 | Page 15 of 20 TRANSFORMER DESIGN Transformers have been designed for use in the circuits shown in Figure 31, Figure 32, and Figure 33 and are listed in Table 13. The design of a transformer for the ADuM3070 can differ from some isolated dc-to-dc converter designs that do not regulate the output voltage. The output voltage is regulated by a PWM controller in the ADuM3070 that varies the duty cycle of the primary side switches in response to a secondary side feedback voltage, VFB, received through an isolated digital channel. The internal controller has a limit of 40% maximum duty cycle. TRANSFORMER TURNS RATIO To determine the transformer turns ratio, and taking into account the losses for the primary switches and the losses for the secondary diodes and inductors, the external transformer turns ratio for the ADuM3070 can be calculated by 2×× += DV VV N N (MIN)DD1 DISO P S where: NS/NP is the primary to secondary turns ratio. VISO is the isolated output supply voltage. VD is the Schottky diode voltage drop (0.5 V maximum). VDD1 (MIN) is the minimum input supply voltage. D is the duty cycle = 0.30 for a 30% typical duty cycle, 40% is maximum, and a multiplier factor of 2 is used for the push-pull switching cycle. For Figure 31, the 5 V to 5 V reference design in Table 13, with VDD1 (MIN) = 4.5 V , the turns ratio is NS/NP = 2. For a similar 3.3 V input to 3.3 V output, isolated single power supply and with VDD1 (MIN) = 3.0 V , the turns ratio is also NS/NP = 2. Therefore, the same transformer turns ratio NS/NP = 2 can be used for the three single power applications (5 V to 5 V , 5 V to 3.3 V , and 3.3 V to 3.3 V). For Figure 32, the circuit uses double windings and diode pairs to create a doubler circuit; therefore, half the output voltage, VISO/2, is used in the equation. = DV VV N N (MIN)DD1 D ISO P S NS/NP is the primary to secondary turns ratio. VISO/2 is used in the equation because the circuit uses two pairs of diodes creating a doubler circuit. VD is the Schottky diode voltage drop (0.5 V maximum). VDD1 (MIN) is the minimum input supply voltage. D is the duty cycle, which is 0.30 for a 30% typical duty cycle and 0.40 for a 40% maximum duty cycle, and a multiplier factor of two is used for the push-pull switching cycle. For Figure 32, the 5 V to 15 V reference design in Table 13, with VDD1 (MIN) = 4.5 V , results in a turns ratio of NS/NP = 3. For Figure 33, the circuit also uses double windings and diode pairs to create a doubler circuit; however, because a positive and negative output voltage is created, VISO is used in the equation. 2×× += DV VV N N (MIN)DD1 DISO P S where: NS/NP is the primary to secondary turns ratio. VISO is the isolated output supply voltage and is used in the equation because the circuit uses two pairs of diodes creating a doubler circuit with a positive and negative output. VD is the Schottky diode voltage drop (0.5 V maximum). VDD1 (MIN) is the minimum input supply voltage, and a multiplier factor of 2 is used for the push-pull switching cycle. D is the duty cycle; in this case, a higher duty cycle of D = 0.35 for a 35% typical duty cycle (40% maximum duty cycle) was used in the Figure 33 circuit to reduce the maximum voltages seen by the diodes for a ±15 V supply. For Figure 33, the +5 V to ±15 V reference design in Table 13, with VDD1 (MIN) = 4.5 V , results in a turns ratio of NS/NP = 5. TRANSFORMER ET CONSTANT The next transformer design factor to consider is the ET constant. This constant determines the minimum V × µs constant of the transformer over the operating temperature. ET values of
14 V × µs and 18 V × µs were selected for the ADuM3070 designs
listed in Table 13 using the following equation: 2)( )( ×= MINSW (MAX)DD1 f V MINET where: VDD1 (MAX) is the maximum input supply voltage. fSW (MIN) is the minimum primary switching frequency = 300 kHz in startup, and a multiplier factor of 2 is used for the push-pull switching cycle. TRANSFORMER PRIMARY INDUCTANCE AND RESISTANCE Another important characteristic of the transformer for designs with the ADuM3070 is the primary inductance. Transformers for the ADuM3070 are recommended to have between 60 µH to 100 µH of inductance per primary winding. Values of primary inductance in this range are needed for smooth operation of the ADuM3070 pulse-by-pulse current-limit circuit, which can help protect against build up of saturation currents in the transformer. If the inductance is specified for the total of both primary windings, for example, as 400 µH, the inductance of one winding is ¼ of two equal windings, or 100 µH. Another important characteristic of the transformer for designs with the ADuM3070 is primary resistance. Primary resistance as low as is practical (less than 1 Ω) helps reduce losses and improves efficiency. The total primary resistance can be measured and specified, and is shown for the transformers in Table 13.
Table 13. Transformer Reference Designs in Table 13 or from other manufacturers. switching frequency is 318 kHz. ceramic capacitor (CFB) in parallel with the high feedback resistor. overshoot and undershoot during load transients. Pin 14 and Pin 15, as close to the chip pads as possible. be used in parallel. See Table 14 for recommended components. of full load are stable with the 47 µH inductor value listed in Table 14. value and a 0.34 A current rating to handle a load to 300 mA. shown in Figure 32 and Figure 33.
Figure 39. 16-Lead Shrink Small Outline Package [QSOP] 1 Tape and reel are available. The addition of an -RL7 suffix designates a 7” (1000 units) tape and reel option. REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
Rev. 0 | Page 20 of 20 NOTES ©2012 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D10437-0-5/12(0)