SPI-8000TW Application Note Dual Output Surface Mounted type Switching Regulator IC SPI-8000TW Series 2nd Edition June 2006 SANKEN ELECTRIC CO., LTD EI-00070 1 SPI-8000TW －－－ Contents －－－ 1. General Description 1-1 Features －－－－－－－－－－ 3 1-2 Applications －－－－－－－－－－ 3 1-3 Type －－－－－－－－－－ 3 2. Specification 2-1 Package Information －－－－－－－－－－ 4 2-2 Ratings －－－－－－－－－－ 5 2-3 Circuit Diagram －－－－－－－－－－ 9 3. Operational Description 3-1 PWM Output Voltage Control －－－－－－－－－－ 12 3-2 Overcurrent Protection / Thermal Shutdown －－－－－－－－－－ 13 4. Terminal Description 3-1 Terminal List －－－－－－－－－－ 14 3-2 Functional Description of Terminal －－－－－－－－－－ 14 5. Cautions 5-1 External Components －－－－－－－－－－ 16 5-2 Pattern Design Notes －－－－－－－－－－ 20 5-3 Operation Notes －－－－－－－－－－ 20 6. Applications 6-1 Soft Start －－－－－－－－－－ 21 6-2 ON/OFF Control of Output by Using Soft Start －－－－－－－－－－ 21 6-3 Output Voltage Setting －－－－－－－－－－ 21 6-4 Reverse Bias Protection －－－－－－－－－－ 22 6-5 Operational Frequency －－－－－－－－－－ 22 7. Terminology －－－－－－－－－－ 23 EI-00070 2 SPI-8000TW 1. General Description The SPI-8000TW series (SPI-8001TW, SPI-8002TW and SPI-8003TW) are a regulator IC provided with various functions required for the buck regulator as well as protection functions against overcurrent and overheat. Two of 1.5A variable outputs are provided in a package for surface mounting to realize a small and highly efficient switching regulator. ● 1-1 Features - Small package, high output current 1.5A HSOP – 16-pin surface mounting package with the maximum output current of 1.5A for each output - High efficiency 80% TYP (SPI-8001TW, VIN = 15V / Io = 0.5A) 78% TYP (SPI-8002TW, VIN = 15V / Io = 0.5A) 78% TYP (SPI-8003TW, VIN = 14V / Io = 0.5A) - Variable output voltage 1 – 16V (SPI-8001TW), 1 – 24V (SPI-8002TW and SPI-8003TW) - Low voltage/high precision reference voltage 1V ±1% and low voltage/high precision - Operational frequency Choke coil can be downsized by means of 250kHz fixed (SPI-8001TW and SPI-8002TW), 200 – 400 kHz variable (SPI-8003TW) and high operating frequency. - Low power consumption 1μA or less at output off. Low power consumption can be realized during standby operation. - Built-in functions The foldback type overcurrent protection and thermal shutdown circuit - Built-in control function Output ON/OFF control function (applicable for each channel), soft start function ● 1-2 Applications For on-board local power supplies, power supplies for OA equipment and stabilization of secondary output voltage of regulator. ● 1-3 Types - Type: Semiconductor integrated circuits (monolithic IC) - Structure: Resin molding type (transfer molding) EI-00070 3 SPI-8000TW 2. Specification ● 2-1 Package Information (excluded gate burr) (visible heat sink width) (heat sink thickness) EI-00070 4 SPI-8000TW ● 2-2 Ratings Absolute Maximum Rating *1 Parameter Symbol Input Voltage VIN VIN Input Voltage VCC VCC Input Voltage VC/E VC/E Rating Unit Condition V 21 (8001TW) V 40 Power Dissipation *2 Pd Junction Temperature Tj (8002TW,8003TW) V 3.0 Glass epoxy board: 70.0cm2 W 135 (Copper foil area: 30.8cm2) (8001TW,8002TW) °C 150 (8003TW) -40 - 135 Storage Temperature (8001TW,8002TW) °C Tstg -40 - 150 Thermal Resistance (Junction and case) Thermal Resistance (8003TW) θj-c 9.0 °C /W θj-a 35.8 °C /W Glass epoxy board: 70.0cm2 (Copper foil area: 30.8cm2) Glass epoxy board: 70.0cm2 (Copper foil area: 30.8cm2) (Junction and ambient) *1 Absolute Maximum Ratings shows the destruction limits. It is required to take care so that even one item does not exceed the specified value for a moment during instantaneous or normal operation. *2 Absolute Maximum Ratings are restricted by thermal shutdown. Recommended Condition *3 Rating Parameter Symbol Unit MIN Input Voltage VIN *4 VIN MAX VO+3 V 20 (8001TW) Input Voltage VCC VCC 4.5 Input Voltage VC/E VC/E Output Voltage Vo Output Current IOUT Junction Temperature in Operation Tjop -30 Temperature in Operation Top -30 38 (8002/3TW) V V 16 (8001TW) 1 24 (8002/3TW) 1.5 135(8001/2TW) V A °C 125(8003TW) 135(8001/2TW) °C 85(8003TW) EI-00070 5 SPI-8000TW *3 Recommended Conditions shows the operation conditions required for maintaining normal circuit functions that are shown in electrical characteristics. It is required to meet the conditions in actual operations. *4 Please refer to figures below for maximum input voltage. 25 50 20 40 Input Voltage VIN [V] Input Voltage VIN [V] Input Voltage Range (8001TW, 8002TW and 8003TW) 15 10 5 38 30 4.75 20 10 8 0 0 0 1 2 3 4 Output Voltage Vo [V] 5 0 2 4 6 8 10 Output Voltage Vo [V] - In the output voltage of 2 – 16V of SPI-8001TW, the input voltage range is Vo +3 – 20V. - In the output voltage of 4. 75 – 24V of SPI-8002TW and SPI-8003TW, the input voltage range is Vo +3 – 38V. - Under the conditions of use of shaded area, oscillation may become unstable due to the degradation of phase margin and the decrease of ON width, therefore the capacity of choke coil L and output capacitor C2 and C3 should be made large. EI-00070 6 SPI-8000TW (Ta=25°C) Electrical Characteristics (SPI-8001TW and SPI-8002TW) *5 Rating Parameter Symbol MIN Setting Reference Voltage VREF Output Voltage ΔVREF/ Temperature Coefficient ΔT Efficiency1 Eff1 TYP Unit Condition V VIN=10V, Vo=1V, IO=0.1A MAX 0.996 1.006 1.016 VIN=10V, Vo=1V, IO=0.1A, ±0.1 mV/°C Ta=-30 - 135°C VIN=VCC=15V,VO=5V, *6 80/78 % Io=0.5A VIN=15V, VO=5V, Io=0.5A, Efficiency2 *6 Eff2 83/81 % VCC=5V VIN=VCC=15V,VO=5V, Operational frequency fosc 250 kHz Io=0.5A VIN=VCC=10 - 20V, Vo=5V, Line Regulation VLine 30 60 mV IO=1A VIN= VCC=15V, Vo=5V, Load Regulation VLoad 10 40 mV IO=0.2 - 1.5A Overcurrent Protection Start Current IS 1.6 A VIN= VCC=15V Circuit Current in Non-operation 1 IIN 4 mA Circuit Current in Non-operation 2 ICC 8.5 mA VCC=15V, IO=0A Circuit Current in Non-operation 3 IIN(off) 1 μA VIN=15V, VC/E=0V or Open Circuit Current in Non-operation 4 ICC(off) 1 μA VCC=15V, VC/E=0V or Open V VIN=VCC=15V V VIN=VCC=15V μA VC/E=20V 0.5 V VIN= VCC=15V 80 μA VSSL=0V, VIN= VCC=15V VIN= 15V, VCC=5V, IO=0A, High level Voltage VC/EH C/E Low level Voltage VC/EL Terminal Flow-out Current IC/EH 2.0 0.8 95 VO≤ 12V at High level Low level Voltage VSSL SS Flow-out Current Terminal *7 ISSL 60 at Low level * The left side and right side of columns of efficiency rating values show that of SPI-8001TW and SPI-8002TW respectively. EI-00070 7 SPI-8000TW Electrical Characteristics (SPI-8003TW) *5 (Ta=25°C) Rating Parameter Symbol Setting Reference Voltage Output Voltage Temperature Coefficient VREF Unit Condition MIN TYP MAX 0.996 1.006 1.016 ΔVREF/ ΔT ±0.1 V VIN=14V, IO=0.1A mV/ VIN=14V, IO=0.1A, °C Ta=-30 - 125°C Efficiency1 *6 Eff1 78 % VIN=VCC=14V,VO=5V,Io=0.5A Efficiency2 *6 Eff2 81 % VIN=14V,VO=5V,Io=0.5A, VCC=5V Operational frequency Fosc 200 400 kHz VIN=14V,IO=0.1A,Cosc=100pF mV Line Regulation VLine 30 60 Load Regulation VLoad 10 40 1.6 VIN=VCC=9 - 18V, Vo=5V, IO=1A VIN= VCC=14V, Vo=5V, mV IO=0.2 - 1.5A Overcurrent Protection Start Current IS A Circuit Current in Non-operation 1 IIN 4 Circuit Current in Non-operation 2 ICC 8.5 Circuit Current in Non-operation 3 IIN(off) 1 μA VIN=14V, VC/E: Low or Open Circuit Current in Non-operation 4 ICC(off) 1 μA VCC=14V, VC/E: Low or Open Circuit Current in Non-operation 5 IIN(SS0V) mA VIN= VCC=14V VIN= 14V, VCC=5V, IO=0A, VO≦12V mA VCC=14V, IO=0A 4 mA VIN= 14V, VCC=5V, IO=0A, SS1=SS2=0V ICC(SS0V Circuit Current in Non-operation 6 8.5 mA VCC=14V, IO=0A, SS1=SS2=0V ) C/E High level Voltage VC/EH Low level Voltage VC/EL 2.0 0.8 Terminal Flow-out Current IC/EH V VIN=VCC=14V V VIN=VCC=14V μA VC/E=20V 95 at High level SS Low level Voltage Terminal Flow-out Current *7 at Low level VSSL ISSL 60 0.5 V VIN= VCC=14V 80 μA VSSL=0V, VIN= VCC=14V *5 The electrical characteristics shall mean the rated characteristic values assured in the case that the IC is operated under the measurement conditions of each column of the above table. *6 Efficiency can be calculated by following equation. (%) Vo Io 100 V IN I IN *7 No. 6 and 11 terminals are a SS terminal and soft start can be made by connecting a capacitor. In addition, it is possible to turn on and off the output by using the SS terminal. The output is stopped by lowering the SS terminal EI-00070 8 SPI-8000TW voltage below Vsst. The switch-over of potential of SS terminal can be made by open collector driving of the transistor etc. In the case that both soft start and ON-OFF of transistor are used, since the discharge current of C4 and C5 flows across the transistor for ON-OFF, protection for limiting current etc. should be made, if the capacitance of capacitors is large. Because the SS terminal is pulled up to the internal power supply of the IC, voltage cannot be applied from outside. ● 2-3 Circuit Diagram Internal Equivalent Circuit (SPI-8001TW and SPI-8002TW) VIN 3 VCC VC/E C1 SPI-8000TW C6 3V 14 Start C/E VREF PReg OSC fdown TSD UVLO RESET 1V ｆ down cut 6 SS1 7 VREF1 PWM Logic Bufferr-Amp ｆ down cut 2 SWout1 4 OCP 3V R5 C4 VIN1 Amp Drive PWM AGND DGND1 5 VIN2 15 L1 Di1 C2 C7 R1 OCP 3V VO1 R2 R6 11 SS2 10 VREF2 PWM Logic C5 Bufferr-Amp Amp AGND Drive SWout2 L2 13 PWM VO2 Di2 DGND2 C3 12 C8 AGND 1、9 R3 R4 Typical Connection Diagram VIN 3 VCC 2 6 C/E VIN1 SWout1 5 4 Ch1 SS1 VREF1 R5 7 L1 VO1 Di1 R1 C2 IREF1 DGND1 C4 C6 VC/E 14 C7 R2 SPI-8000TW 15 C1 VIN2 SWout2 13 VO2 L2 11 R6 C5 12 SS2 Ch2 VREF2 10 Di2 C3 IREF2 DGND2 R3 C8 R4 AGND 1、9 GND GND EI-00070 9 SPI-8000TW Component List Component Rating Recommended Device C1 220μF/50V Electrolytic Capacitor UUD1H221MNR1GS (nichicon) C2, C3 470μF/25V Electrolytic Capacitor UUD1E471MNR1GS (nichicon) C4, C5 1μF/10V Ceramic Capacitor GRM21BR11A105MA01B (MURATA) 0.1μF/50V C6, C7, C8 Ceramic Capacitor GRM21BR11H104MA01B (MURATA) L1, L2 47μH Inductor SLF12575T-470M2R7 (TDK) D1, D2 2A/60V Schottky Barrier Diode SFPB-66 (Sanken) R1, R3 4kΩ (VO=5V) - R2, R4 1kΩ - Internal Equivalent Circuit (SPI-8003TW) VIN 3 VCC 15 C/E VC/E SPI-8003TW 3V Start VREF PReg OSC RESET C4 C1 fdown TSD UVL O 1V 10 Rosc VIN1 8 R7 Cosc 6 R5 ｆ down cut C9 7 OCP 3V PWM Logic SS1 ｆ down cut BufferrAmp AGND C6 AGND Amp C2 OCP VIN2 16 R1 R2 Drive SWout2 14 PWM VO2 L2 Di2 C3 DGND2 13 AGND 1、9 C7 Di1 PWM Logic BufferrAmp VO1 DGND1 5 3V 11 VREF2 L1 SWout1 4 Amp PWM 12 SS2 R6 Drive VREF1 C5 2 C8 R3 R4 EI-00070 10 SPI-8000TW Typical Connection Diagram VIN VCC 2 6 R5 5 C1 R6 C6 SWout1 4 Ch1 SS1 VREF1 7 1 2 SS2 Di1 1 SPI8003TW VIN2 L 1 IREF DGND 1 1 6 1 3 C/E VIN1 C5 C4 VC/E 1 5 3 Ch2 SWout2 1 4 VREF2 1 1 L 2 Di2 IREF DGND 2 AGN D 1? 9 2 COSC 8 C9 GN D VO1 R1 R2 C 2 C 7 VO2 R3 R4 C 3 C 8 ROSC 10 R7 Q1 R8 GN D Component List Component Rating Recommended Device C1 220μF/50V Electrolytic Capacitor UUD1H221MNR1GS (nichicon) C2, C3 470μF/25V Electrolytic Capacitor UUD1E471MNR1GS (nichicon) C5, C6 1μF/10V Ceramic Capacitor GRM21BR11A105MA01B (MURATA) C4, C7, C8 0.1μF/50V Ceramic Capacitor GRM21BR11H104MA01B (MRATA) C9 100pF/10V Ceramic Capacitor GRM21BR11H101MA01B (MURATA) L1, L2 47μH Inductor SLF12575T-470M2R7 (TDK) D1, D2 2A/60V Schottky Barrier Diode SFPB-66 (Sanken) R1, R3 4kΩ (VO=5V - R2, R4 1kΩ - R7 30kΩ - R8 9.1kΩ - The operating frequency can be set by a capacitor added between the COSC and GND and a resistor added between ROSC and GND. In addition, as shown in the above application circuit, it is possible to add and turn on and off the Q1 to modify the operating frequency. In the above example, when Q1 turns on, only R7 (30kΩ) is added, then the operating frequency is about 300kHz. When Q1 turns off, the synthetic resistance of R7 (30kΩ) and R8 (9. 1kΩ) is added, then the operating frequency is about 250kHz. This is recommended for such applications as AM radio receivers, TV sets, audio equipment etc that are susceptible to switching noise. EI-00070 11 SPI-8000TW 3. Operational Description ● 3-1 PWM Output Voltage Control In the SI-8000TW series, the output voltage is controlled by the PWM system and the IC integrates the PWM comparator, oscillator, error amplifier, reference voltage, output transistor drive circuit etc. The triangular wave output (SPI-8001/2TW: 250kHz, SPI-8003TW: 200 – 400kHz) from the oscillator and the output of the error amplifier are given to the input of the PWM comparator. The PWM comparator compares the oscillator output with the error amplifier output to turn on the switching transistor for a time period when the output of the error amplifier exceeds the oscillator output. PWM Control Chopper Type Regulator Basic Configuration Switching Transistor ｽｲｯﾁﾝｸﾞﾄﾗﾝｼﾞｽﾀ VIN L３ D1 PWM Comparator PWMｺﾝﾊﾟﾚｰﾀ VOUT C２ Drive Circuit ドライブ回路 Error誤差増幅器 Amplifier Oscillator 発振器 基準電圧 Reference Voltage The error amplifier output and the oscillator output are compared by the PWM comparator to generate the drive signal of rectangular wave and to drive the switching transistor. On the assumption that the output voltage attempts to rise, the output of the error amplifier is lowered, because the error amplifier is of inverting type. As the output of the error amplifier is lowered, the time period where it falls below the triangular wave level of the oscillator is increased to shorten the ON time of the switching transistor and as a result, the output voltage is maintained constant. As described above, the output voltage is controlled by varying the ON time of the switching transistor with the switching frequency fixed (the higher is VIN, the shorter is the ON time of the switching transistor.) PWM Comparator Operation Diagram The rectangular wave output of the Oscillator Output 発振器出力 switching transistor is smoothed by the Error Amplifier Output 誤差増幅器出力 LC low pass filter composed of a choke coil and a capacitor to supply stabilized DC voltage to the load. ON OFF Switching TransistorEI-00070 Output ｽｲｯﾁﾝｸﾞﾄﾗﾝｼﾞｽﾀ出力 12 SPI-8000TW ● 3-2 Overcurrent Protection / Thermal shutdown In the SPI – 8000TW, in order to suppress the current at short circuited load, the foldback type overcurrent protection circuit is built in. The overcurrent protection circuit detects the peak current of a switching transistor and when the peak current exceeds the set value, the ON Output Voltage Characteristic on Overcurrent Output Voltage 出力 電圧 ここで周波数が低下 Frequency decreasing point time of the transistor is compulsorily shortened to limit the current by lowering the output voltage. When the overcurrent condition is released, the output voltage will be automatically restored. The thermal shutdown circuit detects the semiconductor 出力電流 Output Current junction temperature of the IC and when the junction temperature exceeds the set value, the output transistor is stopped and the output is turned OFF. When the junction temperature drops from the set value for overheat protection by around 15°C, the Output Voltage Characteristic on Thermal Shutdown 出力電圧 Output Voltage output transistor is automatically restored. * Note for thermal shutdown characteristic This circuit protects the IC against overheat resulting from the instantaneous short circuit, but Restoration Setting 復帰設定温度 Temperature Protection Setting Temperature 保護設定温度 it should be noted that this function does not assure the operation including reliability in the 接合温度 Junction Temperature state that overheat continues due to long time short circuit. EI-00070 13 SPI-8000TW 4. Terminal Description ● 4-1 Terminal List SPI-8001TW / SPI-8002TW SPI-8003TW Symbol Symbol Terminal Description Description 1 AGND Ground Terminal AGND Ground Terminal 2 VIN1 Power Input Terminal (ch1) VIN1 Power Input Terminal (ch1) 3 VCC Controller Input Voltage VCC Controller Input Voltage 4 SWout1 Switching Output Terminal (ch1) SWout1 Switching Output Terminal (ch1) 5 DGND1 Drive Ground Terminal (ch1) DGND1 Drive Ground Terminal (ch1) 6 SS1 Soft Start ON/OFF Terminal (ch1) SS1 Soft Start ON/OFF Terminal (ch1) 7 VREF1 Reference Voltage Terminal (ch1) VREF1 Reference Voltage Terminal (ch1) 8 N/C Non-connected Terminal Cosc 9 AGND Ground Terminal AGND 10 VREF2 Reference Voltage Terminal (ch2) Rosc 11 SS2 Soft Start ON/OFF Terminal (ch2) VREF2 Reference Voltage Terminal (ch2) 12 DGND2 Drive Ground Terminal (ch2) SS2 Soft Start ON/OFF Terminal (ch2) 13 SWout2 Switching Output Terminal (ch2) DGND2 Drive Ground Terminal (ch2) 14 C/E Chip Enable Terminal SWout2 Switching Output Terminal (ch2) 15 VIN2 Power Input Terminal (ch2) C/E Chip Enable Terminal 16 N/C Non-connected Terminal VIN2 Power Input Terminal (ch2) Frequency Setting Terminal (for Capacitor) Ground Terminal Frequency Setting Terminal (for Resistor) ● 4-2 Functional Description of Terminal - AGND (terminal No.1 and No.9 for SPI-8001/2/3TW) It is a ground terminal for analogue. - DGND 1, 2 (terminal No.5 and No.12 for SPI-8001/2TW, terminal No.5 and No.13 for SPI-8003TW) It is a ground terminal for power - VIN 1, 2 (terminal No.2 and No.15 for SPI-8001/2TW, terminal No.2 and No.16 for SPI-8003TW) These are input terminals for external main voltage. VIN1 and VIN2 can be connected separately. - VCC (terminal No.3 for SPI-8001/2/3TW) This is a terminal for internal power supply. It should be connected to VIN (No.2, 16 terminals: SPI-8001/2TW, No.2, 16 terminals: SPI-8003TW) or voltage within the recommended operation should be applied. Lower voltage can make less power consumption. - SWOUT 1, 2 (terminal No.4 and No.13 for SPI-8001/2TW, terminal No.4 and No.14 for SPI-8003TW) EI-00070 14 SPI-8000TW It is a switching output terminal. - SS 1, 2 (terminal No.6 and No.11 for SPI-8001/2TW, terminal No.6 and No.12 for SPI-8003TW) This is a terminal for soft start. From connected capacitors C4 and C5, the output voltage can be soft started. It is possible to turn on or off the transistor for each channel by making the voltage of SS terminal 0.5V or lower. Please refer to 6-1 Soft Start of page 21 for details. R5 and R6 are for discharge protection, when an open collector is used for ON/OFF. Without ON/OFF, neither R5 nor R6 is required. - VREF 1, 2 (terminal No.7 and No.10 for SPI-8001/2TW, terminal No.7 and No.11 for SPI-8003TW) This is a terminal for setting the output voltage. The output voltage of Ch1 is set by R1 and R2 and that of Ch2 by R3 and R4. Please refer to 6-3 Output Voltage Setting of page 21 for the method of setting the output voltage. The variable ranges of output voltage are 1 – 16V (SPI-8001TW) and 1 – 24V (SPI-8002/3TW). - C/E (terminal No.14 for SPI-8001/2TW, terminal No.15 for SPI-8003TW) This is a ON/OFF terminal. The output is OFF at 0.8V or lower and ON at 2V or higher. In the case of ON/OFF by using the C/E terminal, both Ch1 and Ch2 are ON/OFF. In the case of OFF at the CE terminal, inflowing current of VIN and VCC is 1μA or less respectively. If the C/E terminal is not used, it should be pulled up to VIN. - COSC, ROSC (terminal No.8 and No.10 for SPI-8003TW) These are terminals for setting the oscillating frequency. The oscillating frequency is set by C9 and R7 (R8). For the method of setting the oscillating frequency, please refer to the operational frequency characteristics of page 22. The variable operation range of oscillating frequency is 200kHz – 400kHz (SPI-8003TW). - N/C (terminal No.8 and No.16 for SPI-8001/2TW) As the N/C terminal is not connected to the internal circuit, it should be open. In order to avoid influence of noise, it should not be used for the repeating pad etc.. EI-00070 15 SPI-8000TW 5. Cautions ● 5-1 External Components 5-1-1 Choke coil L1, L2 The choke coil L supplies current to the load side when the switching transistor is OFF. And the L is one of the most important components in the chopper type switching regulator. In order to maintain the stable operation of the regulator, such dangerous state of operation as saturation state and operation at high temperature due to heat generation must be avoided. The following points should be taken into consideration for the selection of the choke coil. a) The choke coil should be fit for the switching regulator. The coil for a noise filter should not be used because of large loss and generated heat. b) The inductance value should be appropriate. The larger is the inductance of the choke coil, the less is the ripple current flowing across the choke coil, and the output ripple voltage drops and as a result, the overall size of the coil becomes larger. On the other hand, if the inductance is small, the peak current flowing across the switching transistor and diode is increased to make the ripple voltage higher and this operation state is not favorable for maintaining the stable operation. Small Inductance Large Ripple Voltage/ Current Large Inductance Small Ripple Voltage/ Current The larger is the inductance, the smaller will be The smaller is the inductance, the larger will be the ripple current/voltage. But the outer size of the ripple curtent/voltage. the coil becomes larger. Although the outer size of the coil is smaller, the operation is likely to be unstable. The inductance value shown in the specifications should be considered as a reference value for the stable operation and the appropriate inductance value can be obtained by the following equation. ΔIL shows the ripple current value of the choke coil and the lower limit of inductance is set as described in the following. - In the case that the output current to be used is nearly equal to the maximum rating (1.5A) of the SI-8000TW: output current × 0.2 - 0.3 - In the case that the output current to be used is approximately 0.5A or less: output current × 0.5 – 0.6 EI-00070 16 SPI-8000TW L (Vin Vout ) Vout IL Vin f －－－(1) For example, where VIN = 25V, VOut = 5V, ΔIL = 0.3A, frequency = 60KHz, L (25 5) 5 ≒ 222uH 0.2 25 60 10 3 As shown above, the coil of about 220μH may be selected. c) The rated current shall be met. The rated current of the choke coil must be higher than the maximum load current to be used. When the load current exceeds the rated current of the coil, the inductance is sharply decreased to the extent that it causes saturation state at last. Please note that overcurrent may flow since the high frequency impedance becomes low. d) Noise shall be low. In the open magnetic circuit core which is of drum shape, since magnetic flux passes outside the coil, the peripheral circuit may be damaged by noise. It is recommended to use the toroidal type, EI type or EE type coil which has a closed magnetic circuit type core as much as possible. 5-1-2 Input Capacitor C1 The input capacitor is operated as a bypass capacitor of the input circuit to supply steep current to the regulator during switching and to compensate the voltage drop of the input side. Therefore, the input capacitor should be placed as close as to the regulator IC. In addition, in the case that the smoothing capacitor of the AC rectifier circuit is located in the input circuit, the input capacitor may be also used as a smoothing capacitor, but similar attention should be paid. The selection of C1 shall be made in consideration of the following points: a) The requirement of withstand voltage shall be met. b) The requirement of the allowable ripple voltage shall be met. c) The requirement of ESR shall be low type. The ESR type reduces the generation of spike noise. Current Flow of C1 Current Waveform of C1 Ripple Current The ripple current of the input capacitor is increased in accordance with the increase of the load current. If the withstanding voltages or allowable ripple voltages are exceeded or used without derating, it is in danger of causing not only the decreasing the capacitor lifetime (burst, capacitance decrease, equivalent impedance increase, EI-00070 17 SPI-8000TW etc) but also the abnormal oscillations of regulator. Therefore, the selection with sufficient margin is needed. The effective value of ripple current flowing across the input capacitor can be calculated by the following equation. Vin should be the lowest input voltage. Irms 1.2 Vo1 Vo 2 Iout1 1.2 Iout 2 Vin Vin －－－(2) Vo1: output voltage of Ch1, Vo2: output voltage of Ch2, Io1: output current of Ch1, Io2: output current of Ch2. 5-1-3 Output Capacitor C2, C3 The output capacitor C2 composes a LC low pass filter together with a choke coil L and functions as a rectifying capacitor of switching output. The current equivalent to the pulse current ΔIL of the choke coil current is charged and discharged in the output capacitor. Therefore, it is necessary to meet the requirements of withstand voltage and allowable ripple current with sufficient margin like the input capacitor. Additional points to be checked are DC equivalent series resistance (ESR) and capacitance. The following points should be taken into consideration. Current Flow of C2 Current Waveform of C2 Ripple Current The ripple current of the output capacitor is equal to the ripple current of the choke coil and does not vary even if the load current increases or decreases. a) Allowable Ripple Current The ripple current effective value of the output capacitor is calculated by the equation. Irms IL 2 3 －－－(3) b) DC equivalent series resistance (ESR) It is necessary for the stable operation to select the ESR properly. When the ESR is too large or too small, abnormal oscillation due to increase of ripple voltage or insufficient phase margin occurs respectively. The output ripple voltage is determined by a product of the pulse current ΔIL (=C2 discharge and charge current) of the choke coil current and the ESR, and the output ripple voltage which is 0.5 - 1% of the output voltage (for example, where 0.5% at Vout = 5V, 25mV) is good for the stable operation. Please refer to the equations (4) and (5) to obtain the output ripple voltage. It should be noted that the ESR is changeable subject to temperature and it EI-00070 18 SPI-8000TW is especially lowered at high temperature. Vrip Vin Vout Vout ESR L Vin f Vrip IL ESR －－－(4) －－－(5) When the ESR is too low (approx. 10 - 20Ω or lower), the phase delay becomes larger, resulting in abnormal oscillation. Therefore, it is not appropriate that a tantalum capacitor or a laminated ceramic capacitor is used for the output capacitor as an independent component. However, connecting a tantalum capacitor or a laminated ceramic capacitor in parallel with an electrolytic capacitor is effective in reducing the output ripple voltage only when it is used at low temperature (< 0°C). In addition, in order to further decrease the ripple voltage, as shown below, it is also effective to add one stage of the LC filter to form the π type filter. SI-8000TW L2 ： 20uH Co2 ： 200uF It should be noted that the operating stability is more influenced by the ESR than the capacitance as described above if the requirements of withstand voltage and allowable ripple current are met. With respect to the layout of the output capacitor, if it is located far from the IC, it will give same effect as the increase of ESR due to wiring resistance etc., therefore it is recommended to place it near the IC. 5-1-4 Flywheel Diode Di1, Di2 The flywheel diode Di is to discharge the energy which is stored in the choke coil at switching OFF. For the flywheel diode, the Schottky barrier diode must be used. If a general rectifying diode or fast recovery diode is used, the IC may be destroyed by applying reverse voltage due to the recovery and ON voltage. EI-00070 19 SPI-8000TW ● 5-2 Pattern Design Notes SPI-8001/2TW VC/E R6 L2 1pin C5 Di2 16pin 1.271.25±0.25 ±0.25 VO2 R3 C8 R4 C3 VIN GND 1pin C1 C2 C6 (0.4) (0.87) R2 C7 １ R1 pin 9pin VO1 Di1 C4 8pin 1.5±0.1 0.3±0.1 L1 R5 7.5±0.2 (11.1) (4.5) Recommended Land Pattern SPI-8003TW C/E R2 L2 Di2 R４ SS2 C3 R7 C8 16 9 １ 8 Di1 C7 C9 C4 C1 L1 C2 SS1 R1 R3 Recommended Land Pattern *In order to obtain the most suitable operating conditions, one-point GND wiring should be used for the GND line with No. 9 terminal as a center and it is required to lay out each part in the shortest distance. ● 5-3 Operation Notes - It is not possible to operate the output of SPI-800TW in parallel. - Since SPI-8000TW has common GND, it cannot used as a inverted chopper regulator. EI-00070 20 SPI-8000TW 6. Applications ● 6-1 Soft Start When a capacitor is connected to terminal 6 or 11, the soft start is activated when the input voltage is applied. The capacitor C4 and C5 controls the rise time by controlling the OFF period of PWM control. The delay time Td and the start time Ts are calculated approximately by the following equation. However, since in the actual equipment, the operation is affected by input power supply, initial rise of load etc., there may be some variation. Td C4 60 106 Ts C 4 Vo Vin 60 106 (Sec) －－(6) VIN SPI-8000TW 6.11PIN (Sec)－－(7) VOUT C4 C5 Td Ts For example, in the case of VIN = 15V, Vo = 5V and C3 = 1μF, the calculation is as follows: Td 1 106 5 1 106 , 16 . 6 ( ms ) Ts ≒ 5.5(ms ) 60 106 15 60 106 Td Ts ≒ 22.1(ms) Accordingly, after power-on and up to the rising of output voltage, it takes 22.1ms. But if C4 and C5 are made large, it takes time for discharging of C4 and C5 after Vin OFF. It is recommended to use C4 and C5 within the value of 7μF. ● 6-2 ON/OFF Control of Output by Using Soft Start The output ON-Off control is possible using the SS terminal (No.6 and No.11). The output is turned OFF when the terminal 6 and 11 voltage falls to Lo level SPI-8000TW (1.5V or less) by such as open collector. It is possible to 6,11PIN use the soft start together. Since the soft start terminal has been already pulled up, no voltage shall be applied from R5,R6 C4,C5 the external side. R5 and R6 are used for protection during the discharging of C4 and C5. ● 6-3 Output Voltage Setting The output voltage of Ch1 is set by R1 and R2, while that of Ch2 by R3 and R4. When the output voltage is 5V, R1 is 4kΩ and R2 1kΩ. EI-00070 21 SPI-8000TW R1( R3) VO1 V REF1 VO1 1 I REF 1 110 3 ，R 2( R 4) V REF 1 1 ≒1K I REF 1 110 3 ‐‐(8) ● 6-4 Reverse Bias Protection A diode for reverse bias protection will be required between input and output when the output voltage is higher than the input terminal voltage. SFPL52 (Sanken) is recommended for this diode. 2,15 PIN SPI-8000TW 4,13 PIN ● 6-5 Operational Frequency SPI-8003TW Rosc-fosc(Ta=25℃) 500 450 y 3686 x 0.7442 400 fosc(kHz) 350 y 1741.8x 0.7082 300 Cosc=220pF Cosc=100pF 250 200 150 100 50 0 1 10 Rosc(kohm) 100 EI-00070 22 SPI-8000TW 7. Terminology - Jitter It is a kind of abnormal switching operations and is a phenomenon that the switching pulse width varies in spite of the constant condition of input and output. The output ripple voltage peak width is increased when a jitter occurs. - Recommended Conditions It shows the operation conditions required for maintaining normal circuit functions. It is required to meet the conditions in actual operations. - Absolute Maximum Ratings It shows the destruction limits. It is required to take care so that even one item does not exceed the specified value for a moment during instantaneous or normal operation. - Electrical Characteristics It is the specified characteristic value in the operation under the conditions shown in each item. If the operating conditions are different, it may be out of the specifications. - PWM (Pulse Width Modulation) It is a kind of pulse modulation systems. The modulation is achieved by changing the pulse width in accordance with the variation of modulation signal waveform (the output voltage for chopper type switching regulator). - ESR (Equivalent Series Resistance) It is the equivalent series resistance of a capacitor. It acts in a similar manner to the resistor series-connected to the capacitor. EI-00070 23 SPI-8000TW Notice ・The contents of this description are subject to change without prior notice for improvement etc. Please make sure that any information to be used is the latest one. ・Any example of operation or circuitry described in this application note is only for reference, and we are not liable to any infringement of industrial property rights, intellectual property rights or any other rights owned by third parties resulting from such examples. ・In the event that you use any product described here in combination with other products, please review the feasibility of combination at your responsibility. ・Although we endeavor to improve the quality and reliability of our product, in the case of semi-conductor components, defects or failures which occur at a certain rate of probability are inevitable. The user should take into adequate consideration the safety design in the equipment or the system in order to prevent accidents causing death or injury, fires, social harms etc.. ・Products described here are designed to be used in the general-purpose electronic equipment (home appliances, office equipment, communication terminals, measuring equipment etc.). If used in the equipment or system requiring super-high reliability (transport machinery and its control equipment, traffic signal control equipment, disaster/crime prevention system, various safety apparatus etc.), please consult with our sales office. Please do not use our product for the equipment requiring ultrahigh reliability (aerospace equipment, atomic control, medical equipment for life support etc.) without our written consent. ・The products described here are not of radiation proof type. ・The contents of this brochure shall not be transcribed nor copied without our written consent. EI-00070 24