SI-8000S,SS Application Note Full Mold Type Chopper Type Switching Regulator IC SI-8000S, SS Series 9th Edition April 2010 SANKEN ELECTRIC CO., LTD. EI00062-7 SI-8000S, SS －－－ Contents －－－ 1. General Description 1-1 Features －－－－－－－－－－ 3 1-2 Application －－－－－－－－－－ 3 1-3 Type －－－－－－－－－－ 3 2-1 Package Information －－－－－－－－－－ 4 2-2 Ratings －－－－－－－－－－ 5 2-3 Circuit Diagram －－－－－－－－－－ 7 3-1 PWM Output Voltage Control －－－－－－－－－－ 8 3-2 Overcurrent Protection / Thermal Shutdown －－－－－－－－－－ 9 4-1 External Components －－－－－－－－－－ 10 4-2 Pattern Design Notes －－－－－－－－－－ 14 4-3 Operation Waveform Check －－－－－－－－－－ 15 4-4 Power Supply Stability －－－－－－－－－－ 16 4-5 Thermal Design －－－－－－－－－－ 20 5-1 Soft Start －－－－－－－－－－ 23 5-2 Output ON / OFF Control －－－－－－－－－－ 24 5-3 Controllable Output Voltage －－－－－－－－－－ 24 5-4 Spike Noise Reduction －－－－－－－－－－ 26 5-5 Reverse Bias Protection －－－－－－－－－－ 27 5-6 Buck-boost converter －－－－－－－－－－ 27 6. Heat Derating －－－－－－－－－－ 30 7. Typical Characteristics －－－－－－－－－－ 31 8. Terminology －－－－－－－－－－ 39 2. Specification 3. Operational Description 4. Cautions 5. Applications EI00062-7 2 SI-8000S, SS 1. General Description The SI-8000S, SS series is a chopper type switching regulator IC which is provided with various functions required for the buck switching regulator and protection functions. By using four external components, a highly efficient switching regulator can be composed. Products of this series are screened from those of the SI-8000S series for the output voltage. ● 1-1 Features - Compact size and large output current of 3A The maximum output current of 3A for the outline of TO220F class. - High efficiency of 84% (SI-8050S, SS Vin = 20V / Io = 1A) Heat dissipation is small due to high efficiency to allow for the downsizing of a heat sink. - Four external components The regulator can be composed of input / output capacitor, diode and coil. - Internal adjustment of output voltage and phase compensation having been done in production Troublesome adjustment of output voltage and phase compensation by means of external components is no longer required. - Reference oscillation by a built-in timing capacitor No external capacitor for setting the oscillation frequency is required. - Built-in functions for overcurrent and thermal shutdown A current limiting type protection circuit against overcurrent and overheat is built in. (automatic restoration type) - Soft start function (capable of ON / OFF output) By adding an external capacitor, it is possible to delay the rise speed of the output voltage. ON/OFF control of the output is also possible. - No insulation plate required No insulation plate is required, when it is fitted to the heat sink, because it is of full molding type. ● 1-2 Application For on-board local power supplies, power supplies for OA equipment, stabilization of secondary output voltage of regulator and power supply for communication equipment ● 1-3 Type - Type: Semiconductor integrated circuits (monolithic IC) - Structure: Resin molding type (transfer molding) EI00062-7 3 SI-8000S, SS 2. Specification ● 2-1 Package Information 4.2±0.2 φ3.2±0.2 2.8±0.2 8000S (17.9) 16.9±0.3 SK a b 7.9±0.2 4.0±0.2 (0.5) 10.0±0.2 2.6±0.1 (8.0) 0.85+0.2/-0.1 8.2±0.7 0.95±0.15 5.0±0.6 (2.0) S※ 2 0.45+0.2/-0.1 3.9±0.7 ※ P1.7±0.7×4=6.8±0.7 1 2 3 4 5 Pin Assignment 1. VIN 2. SWOUT 3. GND 4. VOS 5. SS (4.3) 8.2±0.7 a. Type Number b. Lot Number 1st letter The last digit of year nd 2 letter Month January to September by Arabic number October to December by O (October), N (November) and D (December) 3rd & 4th letter Day 01 – 31: Arabic Numerical EI00062-7 4 SI-8000S, SS <Notes> * shows the dimensions measured at the top of lead. *2 In the SI-8000SS, the mark “S” is stamped on the right side of SK mark. In the SI-8000S, the mark “S” may be stamped on the right side of SK mark. Unit: mm DWG. NO.: TG3A-1102 ● 2-2 Ratings 2-2-1 Lineup Product Name Vout(V) SI-8033S 3.3 SI-8050S 5 SI-8090S 9 SI-8120S 12 SI-8150S 15 2-2-2 Absolute Maximum Ratings Parameter Symbol Rating Unit Input Voltage VIN 43 *1 V Allowable Power Dissipation Pd1 18 W Pd2 1.5 W Junction Temperature Tj 125 °C Storage Temperature Tstg -40 - +125 °C SW Terminal Vsw -1 V in Infinite Radiation Allowable Power Dissipation without Heat sink Applied Reverse Voltage *1: 35V for SI-8033S and SI-8033SS. 2-2-3 Recommended Conditions Parameter Symbol SI-8033S,SS SI-8050S,SS SI-8090S,SS SI-8120S SI-8150S Unit DC Input Voltage VIN 18 - 40 V Output Current IO Junction Temperature Tjop 5.5 - 28 7 - 40 12 - 40 15 - 40 0-3 A -30 - +125 °C in Operation EI00062-7 5 SI-8000S, SS 2-2-4 Electrical Characteristics (Ta=25°C) SI-8033S Parameter SI-8050S SI-8090S SI-8120S SI-8150S Symbol Unit min typ max min typ Vo S SS Set Output Voltage max min typ max min typ max min typ max 3.17 3.30 3.43 4.80 5.00 5.20 8.55 9.00 9.45 11.5 12.0 12.5 14.25 15.0 15.75 3.234 3.30 3.366 4.90 5.00 5.10 8.73 9.00 9.27 Conditions VIN=15V/Io=1A η ― ― V VIN=20V/Io=1A VIN=21V/Io=1A VIN=24V/Io=1A VIN=25V/Io=1A 84 88 90 91 VIN=20V/Io=1A VIN=21V/Io=1A VIN=24V/Io=1A VIN=25V/Io=1A 60 60 60 60 VIN=20V/Io=1A VIN=21V/Io=1A VIN=24V/Io=1A VIN=25V/Io=1A 40 50 60 60 79 % Efficiency Conditions VIN=15V/Io=1A Switching f Frequency Conditions VIN=15V/Io=1A Input Voltage ⊿Voline – Output Voltage 60 kHz 25 80 Conditions VIN=8 - 28V 100 VIN=10 - 30V 120 VIN=15 - 30V 130 VIN=18 - 30V 130 VIN=21 - 30V mV (Iout=1A) Output Current – Output Voltage ⊿Voload 10 30 10 40 10 40 10 40 10 Conditions VIN=15V VIN=20V VIN=21V VIN=24V VIN=25V Overcurrent Is 3.1 3.1 3.1 3.1 Protection Start Conditions VIN=15V VIN=20V VIN=21V VIN=24V VIN=25V 40 mV (Iout=0.5 - 1.5A) 3.1 A Current Output Voltage Kt ±0.5 ±0.5 ±1.0 ±1.0 ±1.0 mV/°C Temperature Variation EI00062-7 6 SI-8000S, SS ● 2-3 Circuit Diagram 2-3-1 Internal Equivalent Circuit VIN 1 SI-8000S,SS VIN SWOUT L1 2 VOUT 過電流保護 Overcurrent Overcurrent Protection protection 内部電源 Internal Internal Regulator regulator 発振器 Oscillator ﾘｾｯﾄ Reset Oscillator Latch ﾗｯﾁ &and ﾄﾞﾗｲﾊﾞ Latch & driver Driver Reset C1 D1 過熱保護 Thermal Thermal Shutdown shutdown Comparator ｺﾝﾊﾟﾚｰﾀ Compalator C2 VOS 4 ｴﾗｰｱﾝﾌﾟ Error Error amp Amplifier 基準電圧 Reference Reference Voltage voltage S.S GND 5 3 C3 GND GND 2-3-2 Typical Connection Diagram 1 VIN VIN SWOUT SI-8000S,SS VOS C1 S.S 5 GND 3 C3 GND L1 2 VOUT 4 C1 : 50V/1000μF C2 : 50V/1000μF C3 : 0.01μF D1 C2 (only when the soft start function is used) L1 : 150μH GND D1 : RK46 (Sanken Product) EI00062-7 7 SI-8000S, SS 3. Operational Description ● 3-1 PWM Output Voltage Control In the SI-8000S, SS 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 (≈ 60KHz) 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 VOUT ｽｲｯﾁﾝｸﾞﾄﾗﾝｼﾞｽﾀ Switching Transistor VIN ＰＷＭｺﾝﾊﾟﾚｰﾀ PWM Comparator D1 C2 ドライブ回路 Drive Circuit 誤差増幅器 Error Amplifier Oscillator 発振器 基準電圧 Voltage Reference 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 Oscillator 発振器出力 Output Error Amplifier Output 誤差増幅器出力 ON OFF Switching Transistor Output ｽｲｯﾁﾝｸﾞﾄﾗﾝｼﾞｽﾀ出力 The rectangular wave output of the switching transistor is smoothed by the LC low pass filter composed of a choke coil and a capacitor to supply stabilized DC voltage to the load. EI00062-7 8 SI-8000S, SS ● 3-2 Overcurrent Protection / Thermal Shutdown Output Voltage Characteristics in Overcurrent Output Voltage 出力電圧 ここで周波数が低下 Frequency is lowered Output Current 出力電流 The SI-8000S, SS series integrates a current limiting type overcurrent protection circuit. The overcurrent protection circuit detects the peak current of a switching transistor and when the peak current exceeds the set value, the ON time of the transistor is compulsorily shortened to limit the current by lowering the output voltage. When the output voltage further drops to about 50% of the rated value, the switching frequency is lowered to about 30KHz to prevent the current increase at low output voltage. When the overcurrent condition is released, the output voltage will be automatically restored. Output Voltage Characteristics in Thermal Shutdown Output Voltage 出力電圧 Restoration Setting 復帰設定温度 Temperature Protection Setting Temperature 保護設定温度 Junction Temperature 接合温度 The thermal shutdown circuit detects the semiconductor 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 transistor is automatically restored. * Note for thermal shutdown characteristic This circuit protects the IC against overheat resulting from the instantaneous short circuit, but it should be noted that this function does not assure the operation including reliability in the state that overheat continues due to long time short circuit. EI00062-7 9 SI-8000S, SS 4. Cautions ● 4-1 External Components 4-1-1 Choke coil L1 The choke coil L1 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. Large Inductance ｲﾝﾀﾞｸﾀﾝｽ大 Small Ripple Voltage/ ﾘｯﾌﾟﾙ電圧･電流小 Current C2 Small Inductance ｲﾝﾀﾞｸﾀﾝｽ小 Large Ripple Voltage/ ﾘｯﾌﾟﾙ電圧･電流大 Current C2 The larger is the inductance, the smaller will be the ripple current/voltage. But the outer size of the coil becomes larger. The smaller is the inductance, the larger will be the ripple current/voltage. 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 calculated by the equation (1). ΔIL shows the ripple current value of the choke coil and the lower limit of inductance are set as described in the following. - In the case that the output current to be used is nearly equal to the maximum rating (3A) of the SI-8000S, SS: output current × 0.2 – 0.3 - In the case that the output current to be used is approximately 1A or less: output current × 0.3 – 0.4 L1 (VIN VOUT ) VOUT IL VIN f －－－(1) For example, where VIN = 25V, VOUT = 5V, ΔIL = 0.5A, frequency = 60 KHz, EI00062-7 10 SI-8000S, SS L1 (25 5) 5 ≒133uH 0.5 25 60 103 As shown above, the coil of about 130μH may be selected. However, it is to be noted that the peak current of the switching transistor is increased depending on the calculated inductance value. Therefore, the peak current detection system is adopted for overcurrent detection and in this case, the overcurrent detection point may become lower. 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. 4-1-2 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 connected 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. Current Flow of C1 IIN C1電流波形 Current Waveform of C1 VIN 1.VIN ﾘｯﾌﾟﾙ電流 Ripple Current 0 Iv Ip C1 Ton T D Ton capacitor T The ripple current of the input is increased in accordance with the increase of the load current. EI00062-7 11 SI-8000S, SS 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, 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 (2): Vo Io Vin Irms 1.2 －－(2) For instance, where VIN = 20V, Io = 3A, Vo = 5V, Irms 1.2 5 3 0.9 A 20 Therefore, it is necessary to select the capacitor with the allowable ripple current of 0.9A or higher. 4-1-3 Output Capacitor C2 The output capacitor C2 composes a LC low pass filter together with a choke coil L1 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. Current Flow of C2 IL Vout L1 ESR C2電流波形 Current Waveform of C2 Io ﾘｯﾌﾟﾙ電流 Ripple Current 0 RL C2 ⊿IL 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. C2 The ripple current effective value of the output capacitor is obtained by the equation (3). Irms IL 2 3 －－－(3) When ΔIL = 0.5A, Irms 0.5 ≒ 014 . A 2 3 Therefore a capacitor having the allowable ripple current of 0.14A or higher is required. In addition, the output ripple voltage Vrip of the regulator is determined by a product of the pulse current EI00062-7 12 SI-8000S, SS ΔIL of the choke coil current (= C2 charging/discharging current) and the equivalent series resistance ESR of the output capacitor. Vrip IL C2ESR －－－(4) It is therefore necessary to select a capacitor with low equivalent series resistance ESR in order to lower the output ripple voltage. As for general electrolytic capacitors of same product series, the ESR shall be lower, for the products of higher capacitance with same withstand voltage, or with higher withstand voltage (almost proportional to larger externals) with same capacitance. When ΔIL = 0.5A, Vrip = 40mV, C2esr 40 0.5 80m As shown above, a capacitor with the ESR of 80mΩ or lower should be selected. In addition, since the ESR varies with temperature and increases at low temperature, it is required to examine the ESR at the actual operating temperatures. It is recommended to contact the capacitor manufacturers for the ESR value since it is peculiar to capacitors. However, if the ESR of the output capacitor is too low (10 - 30mΩ or lower), the phase margin within the feedback loop of the regulator will be short to make the operation unstable. 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. L1 L2 2.SWOUT 1.VIN SI-8000S,SS 3.GND L2: 20uH 4.VOS D1 C2 C4 C4: 200uF The abnormal oscillation can be caused unless the output voltage detection point (wiring to the Vos terminal) is placed before the second stage filter if the second stage filter is added. Therefore, the care should be taken. 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. 4-1-4 Flywheel Diode D1 The flywheel diode D1 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 EI00062-7 13 SI-8000S, SS recovery diode is used, the IC may be damaged by applying reverse voltage due to the recovery and ON voltage. In addition, since the output voltage from the SWOUT terminal (pin 2) of the SI-8000S, SS series is almost equivalent to the input voltage, the flywheel diode with the reverse withstand voltage of the input voltage or higher should be used. ● 4-2 Pattern Design Notes 4-2-1 High Current Line Since high current flows in the bold lines in the connection diagram, the pattern should be as wide and short as possible. L1 1,VIN VIN 2.SWOUT VOUT SI-8000S,SS 4.VOS C1 5.SS 3.GND C2 D1 GND GND 4-2-2 Input / Output Capacitor The input capacitor C1 and the output capacitor C2 should be connected to the IC as close as possible. If the rectifying capacitor for AC rectifier circuit is on the input side, it can be used as an input capacitor. However, if it is not close to the IC, the input capacitor should be connected in addition to the rectifying capacitor. Since high current is discharged and charged through the leads of input / output capacitor at high speed, the leads should be as short as possible. A similar care should be taken for the patterning of the capacitor. C1,C2 Improper Pattern Example C1,C2 Proper Pattern Example 4-2-3 Sensing Terminal The output voltage sensing terminal Vos shall be connected near the output capacitor C2 as much as possible. (Vos terminal flow-in current is approx. 1mA.) If it is connected far from C2, it should be noted that abnormal oscillation may happen due to the low regulation and increased switching ripple. EI00062-7 14 SI-8000S, SS Board Pattern Example (Top View) ● 4-3 Operation Waveform Check It can be checked by the waveform between the pin 2 and 3 (SWOUT-GND waveform) of the SI-8000S, SS whether the switching operation is normal or not. The examples of waveforms at normal and abnormal operations are shown below: 1. Normal Operation (continuous area) 2. Normal Operation (discontinuous area) 3. When C1 is distant from IC 4. When C2 is distant from IC The continuous area is an area where the DC component of the triangular wave is superimposed on the EI00062-7 15 SI-8000S, SS current flowing across the choke coil and the discontinuous area is an area where the current flowing across the choke coil is intermittent (a period of zero current may happen.) because the current flowing across the choke coil is low. Therefore, when the load current is high, the area is a continuous area and when the same current is low, the area is a discontinuous area. In the continuous area, the switching waveform is formed in the normal rectangular waveform (waveform 1) and in the discontinuous area, damped oscillation is caused in the switching waveform (waveform 2), but this is a normal operation without any problem. In the meantime, when the IC is far from C1 and C2, jitter which disturbs the ON – OFF time of switching will happen as shown in the waveforms (3, 4). As described above, C1 and C2 should be connected close to the IC. ● 4-4 Power Supply Stability 4-4-1 Phase Margin This block diagram shows that the chopper type regulator is a negative feedback amplifier which controls the output voltage by constantly comparing with the output voltage and the reference voltage which is set in advance. Therefore, it has a negative feedback loop to control the output by detecting the variation of output voltage with the error amplifier. L1 Reference Voltage 基 準 電 圧 Control 制御部 Block Reference Voltage 基 準 電 圧 -180deg Negative Feedback Loop 負帰還ﾙｰﾌﾟ ESR C2 Load 負荷 0deg The phase within the negative feedback loop is displaced by 180° to negate the variation of the output voltage, but in the event that the phase is further delayed by 180° in the state that the amplification degree (gain) is 1 or more, the total phase delay amounts to 360° to deviate from the stable operation zone to cause abnormal oscillation. This is called Barkhausen oscillation conditions. Therefore, the oscillation conditions should not be accrued in the actual stabilized power supply. It is possible to judge whether the Barkhausen oscillation conditions are accrued or not by means of frequency and gain/phase characteristics of the negative feedback loop. The frequency-gain/phase characteristics are called Bode diagram. EI00062-7 16 SI-8000S, SS 1-step Differential Amplifier IN OUT Bode Diagram Example Gain ｹﾞｲﾝ 20dB 0dB 0.1fp 9k Phase 位相 -0deg -45deg -90deg 1k Frequency 周波数 fp 10fp In the Bode diagram, the frequency at which the gain is 1 (0 dB) is called gain intersection and the frequency at which the phase of feedback loop is -180° is called phase intersection. Unless the phase reaches -180° at the frequency of gain intersection, the oscillation conditions are not met. In this respect, the phase at gain intersection - (-180°) is equal to the phase at gain intersection +180° and this value is used as a margin to -180° which is called phase margin. The more the phase margin is, the less likely the abnormal oscillation is to occur against the variation of environmental conditions such as input / output conditions and temperature. Therefore, sufficient phase margin should be taken into consideration in order to maintain the stable operation. Stability Judgment at Bode Diagram Gain Characteristics ｹﾞｲﾝ特性 Gainｹﾞｲﾝ特性 Characteristics Gain Intersection ｹﾞｲﾝ交点 0dB Phase Characteristics 位相特性 0dB Frequency 周波数 Gain Intersection ｹﾞｲﾝ交点 Frequency 周波数 Phase 位相特性 Characteristics 位相余裕 Phase Margin (>0) -180deg Phase Intersection 位相交点 Stable 安定な場合 位相交点 Phase Intersection -180deg 不安定な場合 Unstable 位相余裕 Phase Margin (<0) 4-4-2 Phase Characteristics of Regulator IC The phase characteristics of the chopper type regulator are synthesized by the phase characteristics inside the regulator IC and that of the LC filter. The phase characteristics inside the regulator IC are generally determined by the delay time of the control block and the phase characteristic of the output error amplifier. Among these two factors, the phase delay due to the delay time of the control block rarely causes problems EI00062-7 17 SI-8000S, SS in actual use. Therefore, the phase characteristics of the error amplifier are important. With respect to the compensation of phase characteristics of the output error amplifier, there are two types of regulator ICs. One is that compensation is made in the IC in advance, while another type is that external components such as resistors and capacitors are added to the IC for compensation. In the former case, it is only a matter of selection of the LC filter, but in the latter case, appropriate phase compensation should be made in accordance with the application of the product. 4-4-3 Phase Characteristics of LC Filter The phase margin of the chopper type regulator depends largely on the phase characteristics of the LC filter for output smoothing. The phase characteristic of the LC filter theoretically shows the characteristics of a secondary delay factor. Resonance is caused at a specific frequency due to the combination of inductance L1 of coil and of capacitance C2 of the capacitor and at frequency higher than the resonance point, the phase is delayed by 180°at a maximum. The resonance frequency is expressed as shown in the equation (5): ｆLC 1 －－－(5) 2 LC The phase characteristics are 0° if they are lower than the resonance frequency fLC. The phase characteristics are 180° if they are higher than the resonance frequency fLC. Accordingly, when the LC filter for output smoothing shows the theoretical phase characteristics, the phase delay reaches -180° in this filter portion and the phase margin will be zero for this regulator. However, in the actual LC filter, the phase delay of the LC filter is less than 180°because of influence of the equivalent series resistance (ESR) of capacitor. Consequently, the phase margin can be secured for the regulator because of this phase compensation effect of the equivalent series resistance (ESR). LC Filter Phase Characteristics LCﾌｨﾙﾀ位相特性 L1 0deg ESR VIN Phase Delay 位相遅れ VOUT C2 ESR High 大 ESR: ESR: ESR Low 小 -180deg ESR 00 ESR: fLC Frequency 周波数 Generally speaking, when such capacitors as tantalum capacitors or laminated capacitors are used for the output LC filter, the phase delay of filters will be large. Therefore, from the view point of securing the phase margin, use of the electrolytic capacitor is preferable. EI00062-7 18 SI-8000S, SS 4-4-4 Relation of Phase Characteristics of Internal IC and LC Filter As described above, the phase characteristics of the chopper type regulator is almost determined by the phase characteristics of the error amplifier and LC filter. In this respect, the relation between these two characteristics is important. When the gain lowering commencement frequency of the error amplifier, namely the first pole frequency fp and the resonant frequency of the LC filter fLC are closer, the phase margin of the regulator is decreased because of concentrated phase delay. In this respect, the proper distribution of fp and fLC is important. Normally, the phase delay of error amplifier commences from 0.1 times of the first pole frequency fp. In order to avoid the concentration of phase delay, the resonant frequency of the LC filter fLC should be kept to be less than 0.1 times of the first pole frequency fp of the error amplifier. Phase 位相 Phase Characteristics: fpとfLCが近い場合の位相特性 when fp and fLC are close 位相 Phase Phase Characteristics: fpとf LCが離れている場合の位相特性 when fp and fLC are distant fp fp 増幅部 Amplification Section 増幅部 Amplification Section LCﾌｨﾙﾀ LC Filter LC Filter LCﾌｨﾙﾀ fLC -180deg fLC -180deg Synthesized Characteristics 合成特性 Long位相遅れ大 Phase Delay 位相遅れ小 Short Phase Delay Synthesized 合成特性 Characteristics -180deg 周波数 Frequency -180deg 周波数 Frequency Generally, the frequency fp of the chopper type regulator IC is set from several KHz to higher than ten KHz. With respect to the constants of LC filters described in the applications of each regulator IC, if the inductance of coil or capacitance of the capacitor is set to be less than the recommended values, the resonant frequency fLC of the LC filter may rise to decrease the phase margin. Care should be taken to this phenomenon. The constants of peripheral components should be properly selected according to the applications of each EI00062-7 19 SI-8000S, SS regulator IC. 60 630 50 540 40 450 ｹﾞｲﾝ Gain 360 20 270 10 180 0 90 -10 0 位相 Phase -20 Phase (°) 30 位相（゜） Gain (dB ｹﾞｲﾝ（dB） チョッパーReg ゲイン、位相特性例 Typical Characteristics of Gain and Phase -90 -30 -180 -40 100 1000 周波数 （Hz） Frequency (Hz) -270 10000 ● 4-5 Thermal Design 4-5-1 Calculation of Heat Dissipation The relation among the power dissipation Pd of regulator, junction temperature Tj, case temperature Tc, heat sink temperature Tfin and ambient temperature Ta is as follows: Pd (Power dissipation) Pd(損失) Tj: Junction temperature (125℃MAX) Tj ｼﾞｬﾝｸｼｮﾝ温度(125℃MAX) Chip チップ θjc: Thermal resistance between junction and case θ jc(接合－ｹｰｽ間熱抵抗) 5°C / W 5.5℃/W Case ケース Tc: Case temperature (internal frame temperature) Tc ｹｰｽ温度(内部ﾌﾚｰﾑ温度) Heat sink 放熱器 θi: Thermal resistance between case and heat sink) θ i(ｹｰｽ－放熱器間熱抵抗) 0.4 – 0.4～0.6℃/W 0.6°C/ W TTfin fin:放熱器温度 Heat sink temperature θfin: Heat sink thermal resistance θ fin(放熱器熱抵抗) Ta: Ambient temperature Ta 周囲温度 Tj Tc －－－(6) jc Tj Tfin －－－(7) Pd jc i Tj Ta －－－(8) Pd jc i fin Pd EI00062-7 20 SI-8000S, SS The TjMAX is an inherent value for each product, therefore it must be strictly observed. For this purpose, it is required to design the heat sink in compliance with PdMAX, TaMAX (determination of θfin). The heat derating graphically describes this relation. The designing of the heat sink is carried out by the following procedure: 1) The maximum ambient temperature Ta MAX in the set is obtained. 2) The maximum power dissipation PdMAX is obtained. 100 VOUT Pd VOUT Io 1 Vf Io1 VIN x －－－(9) * ηx= efficiency (%), Vf= diode forward voltage 3) The size of heat sink is determined from the intersection of the heat derating. The required thermal resistance of the heat sink can be also calculated. The thermal resistance required for the heat sink is obtained by the following equation: i fin Tj Ta jc Pd －－－(10) An example of heat calculation for using SI-8050S under the conditions of VIN = 10V, Io = 3A and Ta = 85°C is shown below. Where efficiency η = 77% , Vf = 0.5V from the typical characteristics, 5 100 Pd 5 3 1 0.5 3 1 ≒373 . W 77 10 125 85 i fin 55 . ≒5.22ﾟC / W 373 . As a result, the heat sink with the thermal resistance of 5°C /W or less is required. As described above, the heat sink is determined, but the derating of 10 – 20% or more is used. Actually, heat dissipation effect significantly changes depending on the difference in component mounting. Therefore, heat sink temperature or case temperature should be checked with the heat sink mounted. 4-5-2 Installation to Heat sink Selection of silicon grease When the SI-8000S, SS is installed to the heat sink, silicon grease should be thinly and evenly coated between the IC and heat sink. Without coating, thermal resistance θi is significantly increased because of contact failure due to micro concavity/convexity between the backside of the IC and the surface of the heat sink to accelerate the heating of the IC, resulting in shorter life of the IC. In some kind of silicon grease to be used, oil component may be separated to penetrate into the IC, resulting in the deformation of packages or the adverse effect on built-in elements. Any other silicon grease than one based on the modified silicon oil shall not be used. The recommended silicon greases are as follows: EI00062-7 21 SI-8000S, SS Sanken’s recommended silicon greases: Types Suppliers G746 Shin-Etsu Chemical Co., Ltd. SC102 Toray Silicone Co., Ltd. YG6260 Momentive Performance Materials Inc. Tightening torque of fixing screws In order to keep the thermal resistance between the IC and the heat sink at low level without damaging the IC package, it is necessary to control the torque of fixing screws in a proper way. Even if silicon grease is coated, the thermal resistance θi increases if the tightening torque is not enough. Change rate of thermal resistance (%) 熱抵抗変化率（%） For the SI-8000S, SS, 58.8 – 68.6N cm (6.0 – 7.0 kg cm) are recommended. 110 105 100 95 90 0 20 40 60 締め付けトルク（N・cm） Tightening Torque (N cm) 80 100 * 1. The change rate of thermal resistance in the case that 58.8N cm (6kg cm) is expressed as 100% is shown above. * 2. The silicon grease G746 shall be used. EI00062-7 22 SI-8000S, SS 5. Applications ● 5-1 Soft Start When a capacitor is connected to terminal 5, the soft start is activated when the input voltage is applied. The capacitor C3 controls the OFF period of PWM control to control the start -up time, and the delay time Td and the start-up time Ts are obtained by the following equation. It should be, however, noted that in the actual equipment, slight fluctuation may happen due to the effects from input power supplies, load start-up etc. The terminal 5 should be open, when the soft start is not used. VIN SI-8000S,SS 5.SS VOUT C3 Td Ts 0.7 C3 (Sec) －－(11) 20 10 6 Vo 0.9 C 3 (Sec)－－(12) Ts Vin 20 106 Td For example, when VIN = 20V, Vo = 5V and C3 = 1μF, Td and Ts are obtained as follows: 0.7 1 10 6 35( ms) 20 10 6 Td Ts≒47( ms ) Td Ts 5 0.9 1 106 ≒12(ms) 20 20 106 As shown above, it takes 47 ms from power-on to output voltage start-up. However, when C3 is made larger, it takes longer time for discharging the C3 after VinOFF. It is recommended to use C3 at the value of 10μF or less. Under the load condition of discontinuous mode (light load), Ts may be shorter than the above-calculated value. ● 5-2 Output ON / OFF Control The output ON-Off control is possible using the soft start (No.5) terminal. The output is turned OFF when the terminal 5 voltage falls to low by such as open collector. It is possible to use the soft start together. Since the soft start terminal has been already pulled up, no voltage shall be applied from the external side. EI00062-7 23 SI-8000S, SS SI-8000S,SS SI-8000S,SS 5.SS 5.SS C3 ON/OFF SS+ON/OFF ● 5-3 Controllable Output Voltage The output voltage can be increased by adding a resistor to the Vos terminal (pin 4). (not applicable for voltage fall) 5-3-1 Variable Output Voltage by One External Resistor L1 VOUT' 2.SWOUT SI-8000S,SS 3.GND D1 Rex 4.VOS Ivos C2 GND The output voltage adjustment resistance Rex is calculated by the following equation. Re x Vout'Vos －－－(13) Ivos Vos: Set output voltage for product Vout: Variable output voltage Ivos: Vos terminal in-flow current≒1mA * Since no temperature compensation is made for Rex, the temperature characteristic of output voltage is lowered. Ivos is variable at maximum ±20% depending on each IC product. Therefore, as the variation range of the output voltage becomes wider, the semi-fixed type resistor is required for the adjustment of accurate output voltage. The variation range of the output voltage including the variation of Rex, Ivos and Vos is shown as follows: - Maximum output voltage (Vout MAX) VOUT' MAX＝VosMAX＋RexMAX IvosMAX －－－(14) VosMAX: The maximum value of set output voltage. The MAX value of the set output voltage should be put, shown in the electrical characteristics of the specifications in page 6. RexMAX: The maximum value of Rex. It is obtained from the allowable tolerance. EI00062-7 24 SI-8000S, SS IvosMAX: The maximum in-flow current of Vos terminal. 1.2mA - The minimum output voltage (Vout MIN) Vout' MIN＝VosMIN＋RexMIN IvosMIN －－－(15) VosMIN: The minimum value of set output voltage. The MIN value of the set output voltage should be put, shown in the electrical characteristics of the specifications in page 6. RexMAX: The minimum value of Rex. It is obtained from the allowable tolerance of resistance. IvosMIN: The minimum in-flow current of Vos terminal. 0.8mA 5-3-2 Variable Output Voltage by Two External Resistors L1 VOUT' 2.SWOUT SI-8000S,SS 3.GND D1 Ivos Rex1 IRex2 Rex2 4.VOS C2 GND The output voltage adjustment resistors Rex1 and 2 are obtained by the following equation. Vout'Vos S IVos Vos Re x2 (S 1) IVos Re x1 －－－(16) －－－(17) S: Stability coefficient The tolerance of temperature characteristics and output voltage is improved more by bypassing the current to Rex2 than the method 5-3-1. Stability coefficient S means the ratio of Rex 2 to the Vos terminal in-flow current Ivos. The larger is S, the more is the variation of temperature characteristic and output voltage improved. (Normally, about 5 – 10) The tolerance of the output voltage including variation of Rex 1, Rex 2, Ivos, Vos is shown below. - Maximum output voltage (Vout' MAX) Vout' MAX ＝VosMAX ＋Rex1MAX( VosMAX －－－(18) ＋IvosMAX ） Rex2MIN VosMAX: The maximum value of set output voltage. The MAX value of set output voltage should be put, shown in the electrical characteristics of the specifications in page 6. Rex1MAX: The maximum value of Rex1. It is obtained from the tolerance of the resistor. Rex2 MIN: The minimum value of Rex2. It is obtained from the tolerance of the resistor. IvosMAX: The maximum in-flow current of Vos terminal. 1.2mA - The minimum output voltage (Vout MIN) EI00062-7 25 SI-8000S, SS Vout' MIN＝VosMIN＋Rex1MIN( VosMIN －－－(19) ＋IvosMIN ） Rex2MAX VosMIN: The minimum value of the set output voltage. Please fill in the MIN value of the set output voltage which is shown in the electrical characteristics of the specifications in page 6. Rex1 MIN: The minimum value of Rex1. It is obtained from the tolerance of the resistor. Rex2MAX: The maximum value of Rex2. It is obtained from the tolerance of the resistor. IvosMIN: The minimum in-flow current of Vos terminal. 0.8mA 5-3-3 Cautions for variation of output voltages The degradation of regulation and the increase in the output voltage temperature coefficient are assumed when the output voltage is varied. If it is varied drastically, the increase of coil capacitance value may be required since the overcurrent protection current is assumed to be lowered due to the increase in coil current. Therefore, the use within the set output voltage +5V is recommended as for the upper limit of output voltage variation. In addition, the MAX value of the set output voltage is recommended as for the lower limit of output voltage variation. ● 5-4 Spike Noise Reduction In order to reduce the spike noise, it is possible to compensate the output waveform of the SI-8000S, SS and the recovery time of the diode by a capacitor, but it should be noted that the efficiency is also slightly reduced. 0～20Ω 1.VIN 100～3000pF 2.SWOUT SI-8000S,SS 0～20Ω 3.GND 100～4000pF Without noise reduction circuit With noise reduction circuit A resistor of 10Ω and a capacitor of 2200pF are connected to external resistor EI00062-7 26 SI-8000S, SS * When the spike noise is observed with an oscilloscope, the lead wire may function as an antenna and the spike noise may be observed extremely higher than usual if the probe GND lead wire is too long. In the observation of spike noise, the probe lead wire should be as short as possible and be connected with the root of the output capacitor. ● 5-5 Reverse Bias Protection A diode for reverse bias protection is required between input and output when the output voltage is higher than the input terminal voltage, such as in battery chargers. SI-8000S,SS ● 5-6 Buck-boost converter 5-6-1 Choke coil L1, diode D1 current rating Since the circuitry of the buck-boost converter is different from that of the buck converter, current flowing across the choke coil L1 and the diode D1 is large. The peak current can be calculated by the equation 20. As seen in this equation, the lower is the input voltage, the larger is the peak current, therefore the choke coil and diode which can meet the peak current at the lowest input voltage should be selected. Ip Io max(Vin min | Vo |) Vin min | Vo | 1 －－－(20) Vin min Vin min | Vo | 2 L1 fosc fosc: 60kHz, L1: Choke coil inductance, It should be calculated by the equation 24. 5-6-2 Ripple current of input/output capacitor C1 and C2 In comparison with the buck converter, large ripple current flows across the output capacitor C2, therefore care should be taken of the allowable ripple current. The ripple current (Colrms) of the output capacitor can be calculated by the equation 22. Since the ripple current is large in the buck-boost converter in comparison with the boost converter, it is recommended to use products with low ESR. The ripple current (CinIrms) of the input capacitor is obtained by the equation 21. CinIrms 1 2 Vo 2 Ip Iv 2 －－－(21) Ip IpIv Iv Vo Vin 3 4Vin Vo CoIrms Vin 1 2 Vin 2 Ip Iv 2 －－－(22) Ip IpIv Iv Vo Vin 3 4Vin Vo Vo Iv Iload Vin Vo Vin Vin Vo Vin Vo 1 －－－(23) 2 L1 fosc EI00062-7 27 SI-8000S, SS Ip: Maximum value of peak current, Iv: Minimum value of peak current, Iload: Continuous current 5-6-3 Choke coil L1 capacitance Since the circuitry of the buck-boost converter is different from that of the buck converter, the choke coil capacitance is unable to be calculated by the same design procedure as that of the buck converter. In the case of the buck converter, as the energy stored in the coil becomes the output power, the inductance L1 of the choke coil can be calculated by the equations 24 and 25. L1 ton Vin 2 ton 2 fosc －－－(24) 2 Vo Io max Vo Vo Vin min fosc －－－(25) 5-6-4 Input voltage and output current ranges Input voltage, output current and peak current ranges in the case that the SI-8000S and SS series are used as a buck-boost converter are shown below, but the actual operational values should be evaluated sufficiently. - Input voltage: The sum of input voltage and output voltage is applied between the emitter and collector of the switching transistor; therefore the maximum input voltage is 40V - Vo. As the peak current increases rapidly, the input voltage range is 10 - 40Vo (V). - Output current: The maximum output current is around 0.8A subject to the inductance of the choke coil. - Peak current: In the case that the peak current is large, as the overcurrent protection is likely to be operated, the peak current should be 3A or lower. Although the peak current can be calculated by the equation 20, it should be checked in the actual operation. 5-6-5 Circuit Example -5V/0.5A VIN +12V 33uH VIN SW SI-8050S Vos 470μ F/25V GND 3 4 SS 5 1500μ F/10V Di VOUT -5V/0.5A EI00062-7 28 SI-8000S, SS -12V/0.5A VIN +12V 47uH VIN SW SI-8120S Vos 1000μ F/25V GND 3 SS 5 4 Di 1000μ F/25V VOUT -12V/0.5A * Care should be taken for GND of the output side. EI00062-7 29 SI-8000S, SS 6. Heat Derating 20 V 100 PD VO I O 1 VF I O 1 O x VIN Infinite heat sink VO: Output Voltage 15 VIN: Input Voltage IO : Output Current η : Efficiency (%) VF: Forward Voltage of Diode Pd (W) Allowable Power Dissipation 許容損失 200×200×2mm (2.3°C /W) RK46…0.5V (IO=3A) 10 100×100×2mm (5.2°C /W) 75×75×2mm (7.6°C /W) 5 With no heat sink 0 -25 0 25 50 75 100 125 Ambient Temperature Ta (°C) Note1. Since the efficiency is subject to change depending on the input voltage and output current,it should be obtained from the efficiency curve of Fig. 4-2, and be substituted in percent. Note2. The thermal design of Di should be made separately. EI00062-7 30 SI-8000S, SS 7. Typical Characteristics - SI-8033S, SS (1) Efficiency (2) Output Voltage Rising 5 100 Output Voltage VO (V) 90 Efficiency η (%) 80 VIN=28V 70 15V 6V 60 8V 50 *Load=C.C 4 3 IO=0A 2 1A 3A 1 40 0 30 0 0.5 1.0 1.5 2.0 2.5 0 3.0 4 6 8 10 Input Voltage VIN (V) 2 Output Current IO (A) (4) Overcurrent Protection Characteristics 3.40 5 3.35 4 Output Voltage VO (V) Output Voltage VO (V) (3) Output Voltage Variation 3.30 3.25 VIN=28V 15V 8V 6V 3.20 3.15 0 12 3 VIN=6V 15V 28V 2 1 0 0.5 1.0 1.5 2.0 2.5 Output Current IO (A) 3.0 0 1 2 3 4 5 Output Current IO (A) 6 EI00062-7 31 SI-8000S, SS Efficiency η (%) 3 3.35 80 η 70 3.30 VO Frequency fo (kHz) Output Voltage VO (V) 4 2 TSD OFF 1 TSD ON 0 50 75 100 125 150 175 Ambient Temperature Ta (°C) 200 3.25 60 fo 50 3.20 3.15 40 -50 -25 0 25 50 75 100 Ambient Temperature Ta (°C) SI-8050S, SS (1) Efficiency (2) Output Voltage Rising * Load=C.C 10 100 80 VIN=40V 20V 10V 70 7V 60 50 40 30 0 0.5 1.0 1.5 2.0 2.5 Output Current IO (A) 3.0 Output Voltage VO (V) (%) 90 Efficiency η - (6) Temperature Characteristics VIN=15V, IO=1A 3.40 90 8 6 4 VIN=7V 20V 40V 2 0 0 1 2 3 4 5 Output Current IO (A) 6 EI00062-7 32 Output Voltage VO (V) (5) Thermal Shutdown VIN=15V, IO=0A 5 SI-8000S, SS (4) Overcurrent Protection Characteristics 10 8 8 Output Voltage VO (V) (3) Output Voltage Variation 6 IO=0A 4 1A 3A 2 6 4 2 TSD OFF 0 0 2 4 6 8 10 Input Voltage VIN (V) (5) Thermal Shutdown VIN=20V, IO=0A 5.10 5.05 100 5.15 90 5.10 80 VIN=40V 20V 4.95 10V 7V 4.90 0 0.5 1.0 1.5 2.0 2.5 3.0 Output Current IO (A) η 5.05 VO Frequency fo (kHz) 5.00 75 100 125 150 175 200 Ambient Temperature Ta (°C) (6) Temperature Characteristics VIN=20V, IO=1A Efficiency η (%) 5.15 Output Voltage VO (V) 0 50 12 TSD ON 70 5.00 60 4.95 fo 50 -50 4.90 -25 0 25 50 75 100 Ambient Temperature Ta (°C) EI00062-7 33 Output Voltage VO (V) Output Voltage VO (V) 10 SI-8000S, SS - SI-8090S, SS 100 (1) Efficiency (2) Output Voltage Rising *Load=C.C 10 90 80 8 21V Output Voltage VO (V) Efficiency η (%) VIN=40V 12V 70 60 50 40 30 1A 3A 4 2 0 0 0.5 1.0 1.5 2.0 2.5 Output Current IO (A) 3.0 0 (3) Output Voltage Variation 9.3 10 9.2 8 9.1 VIN=40V 9.0 21V 8.9 2 4 6 8 10 Input Voltage VIN (V) 12 (4) Overcurrent Protection Characteristics Output Voltage VO (V) Output Voltage VO (V) IO=0A 6 12V 8.8 6 VIN=12V 21V 40V 4 2 0 0 0.5 1.0 1.5 2.0 2.5 Output Current IO (A) 3.0 0 1 2 3 4 5 Output Current IO (A) 6 EI00062-7 34 SI-8000S, SS 8 6 TSD OFF 9.3 90 9.2 4 2 50 75 100 125 150 175 Ambient Temperature Ta (°C) η 80 TSD ON 0 200 9.1 VO 70 9.0 60 8.9 fo 50 8.8 -50 -25 0 25 50 75 100 Ambient Temperature Ta (°C) SI-8120S (1) Efficiency (2) Output Voltage Rising 25 90 20 80 Output Voltage VO (V) 100 Efficiency η (%) - 100 VIN=40V 24V 15V 70 60 50 15 10 IO=0A 5 1A 3A 40 30 0 * Load=C.C 0 0.5 1.0 1.5 2.0 2.5 Output Current IO (A) 3.0 0 5 10 15 20 25 30 Input Voltage VIN (V) EI00062-7 35 Output Voltage VO (V) Efficiency η (%) (6) Temperature Characteristics VIN=21V, IO=1A Frequency fo (kHz) Output Voltage VO (V) (5) Thermal Shutdown VIN=21V, IO=0A 10 SI-8000S, SS 12.2 20 Output Voltage VO (V) 12.3 (4) Overcurrent Protection Characteristics 25 12.1 VIN=40V 12.0 24V 11.9 15V 15 10 0.5 1.0 1.5 2.0 2.5 Output Current IO (A) 3.0 0 Efficiency η (%) 15 80 10 70 20 TSD OFF TSD ON 75 100 125 150 175 Ambient Temperature Ta (°C) 200 1 2 3 4 5 Output Current IO (A) 6 (6) Temperature Characteristics VIN=24V, IO=1A 100 25 0 50 40V 5 Frequency fo (kHz) (5) Thermal Shutdown VIN=24V, IO=0A 5 24V 90 60 12.3 12.2 η 12.1 VO 12.0 11.9 fo 50 -50 11.8 -25 0 25 50 75 Ambient Temperature Ta (°C) 100 EI00062-7 36 Output Voltage VO (V) 0 VIN=15V 0 11.8 Output Voltage VO (V) Output Voltage VO (V) (3) Output Voltage Variation SI-8000S, SS - SI-8150S (1) Efficiency (2) Output Voltage Rising 25 100 20 VIN=40V 25V 18V 80 Output Voltage VO (V) Efficiency η (%) 90 70 60 50 40 30 0 15 10 IO=0A 5 1A 3A 0 0.5 1.0 1.5 2.0 2.5 Output Current IO (A) 3.0 0 5 10 15 20 25 30 Input Voltage VIN (V) 15.3 (4) Overcurrent Protection Characteristics 25 15.2 20 Output Voltage VO (V) (3) Output Voltage Variation Output Voltage VO (V) * Load=C.C 15.1 15.0 VIN=40V 25V 14.9 15 10 VIN=18V 25V 40V 5 18V 14.8 0 0 0.5 1.0 1.5 2.0 2.5 Output Current IO (A) 3.0 0 1 2 3 4 5 Output Current IO (A) 6 EI00062-7 37 SI-8000S, SS 100 20 15 TSD OFF TSD ON 5 0 50 15.2 η 80 75 100 125 150 175 Ambient Temperature Ta (°C) 200 Frequency fo (kHz) 10 90 15.3 70 60 15.1 VO 15.0 14.9 fo 50 -50 14.8 -25 0 25 50 75 Ambient Temperature Ta (°C) 100 EI00062-7 38 Output Voltage VO (V) 25 Output Voltage VO (V) (6) Temperature Characteristics VIN=25V, IO=1A Efficiency η (%) (5) Thermal Shutdown VIN=25V, IO=0A SI-8000S, SS 8. 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 / 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 values 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. EI00062-7 39 SI-8000S, SS 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. EI00062-7 40