SI-8000FDL Application Note Chopper Type Switching Regulator IC SI-8000FDL Series 1st Edition January 2010 SANKEN ELECTRIC CO., LTD. SI-8000FDL －－－ Content －－－ 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 －－－－－－－－－－ 15 4-3 Operation Waveform Check －－－－－－－－－－ 18 4-4 Power Supply Stability －－－－－－－－－－ 19 4-5 Thermal Design －－－－－－－－－－ 23 5-1 Output ON / OFF Control －－－－－－－－－－ 24 5-2 Spike Noise Reduction －－－－－－－－－－ 24 5-3 Reverse Bias Protection －－－－－－－－－－ 25 6. Typical Characteristics －－－－－－－－－－ 26 7. Terminology －－－－－－－－－－ 29 2. Specification 3. Operational Description 4. Cautions 5. Applications 2 SI-8000FDL 1. General Description The SI-8001FDL is a chopper type switching regulator IC which is provided with various functions required for the buck switching regulator and protection functions. By using six external components, a highly efficient switching regulator can be composed. ● 1-1 Features - Compact size and large output current of 3.5A The maximum output current of 3.5 A for the outline of TO263-5 class - High efficiency of 83% (VIN = 15V/IO = 2A) Heat dissipation is small due to high efficiency to allow for the downsizing of a heat sink. - Six external components The regulator can be composed of input / output capacitor, diode, coil and resistors of Vout setting. - 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) - ON/OFF function that turns the output ON and OFF. Voltage is inputted from outside to enable ON/OFF function. Active Low of ON at Low (ON at Open) When the voltage of ON/OFF terminal (Vc terminal) falls below the threshold, the output is turned on (active low). The ON/OFF terminal (Vo terminal) is open. - 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 Applications 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) 3 5-0.80±0.10 φ 1.50 Dp : ±0.20 4-[1.70±0.25] 9.20±0.20 4.90±0.20 (15°) 15.30±0.30 (0.50) (R0.30) 3-(R0.30) 4.50±0.20 PIN assignments 1. ＩＮ 2. SW 3. GND 4. ADJ 5. SS (3°) (3°) 2.00±0.10 (0.75) 9.90±0.20 15.30±0.30 0～6° 2.54 ±0.30 (R0.30) 2.40±0.20 (3°) +0.15 -0.10 +0.10 -0.05 0.10 1.30 (1.75) (4.60) (0.40) 4-[1.70±0.25] 4.90±0.20 9.20±0.20 (6.80) Notes: 1) Dimensions do not include molding burr. ) are shown 2) Figures in parentheses ( only for reference. 3) Figures in parentheses [ ] are dimensions after lead forming. 4) Backside bumps: 0.8 mm at maximum 5) Unit: mm 5-0.80±0.10 2x(R0.45) (4.40) (8.00) 10.00±0.20 SI-8000FDL 2. Specification Unit: mm ●2-1 Package Information Products Weight: Approx.1.48g 4 SI-8000FDL ● 2-2 Ratings 2-2-1 Absolute Maximum Ratings Parameter Symbol Rating Unit Input Voltage VIN Allowable Power Dissipation Pd 3 Junction Temperature Tjmax 150 Storage Temperature Tstg -40 -+150 43 *1 V *2 *1 W °C °C *1 Since the thermal shutdown is provided, it may be operated at Tj > 130°C. *2 Glass epoxy single side board 40 × 40 mm (when copper foil area is 100%) 2-2-2 Recommended Conditions Parameter Symbol SI-8001FDL Unit DC Input Voltage VIN Vo+3v - 40*3 V Output Current IO Junction Temperature in Operation Tjop 0 - 3.5 *4 A -30 - ＋125 °C *3 VIN = 4.5V or Vout +3V, whichever higher value is recommended. *4 It should be used within the temperature range which does not exceed Tjmax. 5 SI-8000FDL (Ta=25°C, Vo=5V, R1=4.2kΩ, R2=0.8kΩ) 2-2-3 Electrical Characteristics Limits Parameter Reference Voltage Symbol VADJ MIN TYP MAX 0.784 0.800 0.816 Unit Test Conditions V VIN=15V, IO=0.2A VIN=15V Reference Voltage Temperature ΔVADJ/ΔT ±0.1 mV/°C IO=0.2A, Coefficient TC=0 - 100℃ Efficiency *6 η Operating Frequency fO Line Regulation Load Regulation 83 % VIN=15V, IO=2A 330 kHz VIN=15V, IO=2A VLine 80 mV VIN=10 - 30V, IO=2A VLoad 50 mV 270 300 VIN=15V, IO=0.2 - 3.5A Overcurrent Defection IS Quiescent Current 1 Iq 3.6 6 A VIN=15V mA VIN=15V, IO=0A VC Terminal Control VC, IH 0.8 V Voltage (ON) ON/OFF VC Terminal Control Terminal *7 Voltage (OFF) VC, IL 2.0 V ON/OFF Control IC, IH 6 100 μA VC=2V Iq(off) 30 200 μA VIN=15V, VC=2V Current at ON Quiescent Current 2 *5 Electrical characteristics indicate specific limits, which are guaranteed when IC is operated under the test conditions shown above in the circuit diagram (refer to P.6). *6 Efficiency is calculated by the following equation. η(%)= VO･IO VIN･IIN ×100 *7 If VC terminal is OPEN, output will be ON state. As input level is equivalent to LS-TTL direct drive by LS-TTL is possible. 6 SI-8000FDL ● 2-3 Circuit Diagram 2-3-1 Internal Equivalent Circuit Overcurrent Protection Latch and Driver Reset Oscillator Comparator Thermal Protection Error Amp. Reference Voltage 2-3-2 Typical Connection Diagram C1: 470μF C2: 680μF L1: 47μH Di: SPB-G56S (Sanken Product) 7 SI-8000FDL 3. Operational Description ● 3-1 PWM Output Voltage Control The SI-8000FDL series controls the output voltage by the PWM system and comprises PWM comparator, oscillator, error amplifier, reference voltage, output transistor drive circuit etc. For the input of the PWM comparator, the triangular wave output (≈300KHz) from the oscillator and the output of the error amplifier are given. The PWM comparator compares the oscillator output with the error amplifier output to control to turn on the switching transistor at the time when the error amplifier exceeds the error amplifier output. PWM Control Chopper Type Regulator Basic Configuration VIN VOUT Switching Transistor ｽｲｯﾁﾝｸﾞﾄﾗﾝｼﾞｽﾀ PWM Comparator ＰＷＭｺﾝﾊﾟﾚｰﾀ D1 The error amplifier output and oscillator C2 output are compared by the PWM ドライブ回路 Drive Circuit comparator to generate the rectangular Error Amplifier 誤差増幅器 wave signal and this signal is inputted Oscillator 発振器 基準電圧 Reference Voltage into the drive circuit to drive the switching transistor. On the assumption that the output voltage commences to rise, the output of the error amplifier will drop, because the error amplifier is of inverting type. As the output of the error amplifier falls down, the time period during which 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 at a certain level. As described above, the output voltage is controlled by varying the ON time of the switching transistor, while fixing the switching frequency. (the higher is Vin, the larger is the ON time of the switching transistor.) PWM Comparator Operation Diagram 発振器出力 Oscillator Output Error Amplifier 誤差増幅器出力 ON OFF Output ｽｲｯﾁﾝｸﾞﾄﾗﾝｼﾞｽﾀ出力 Switching Transistor Output The rectangular wave output of the switching transistor is smoothed by the LC low pass filter of a choke coil and capacitor to supply stabilized DC voltage to the load. 8 SI-8000FDL ● 3-2 Overcurrent Protection / Thermal Shutdown Output Voltage Characteristics in Overcurrent Output Voltage As Vo drops, the oscillating frequency is lowered. Output Current The SI-8000FDL 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. In addition, when the output voltage is lowered, the increase of current at low output voltage is prevented by dropping linearly the switching frequency to about 25 KHz. 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 (around 150°C), 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. 9 SI-8000FDL 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. When the ripple voltage of the output voltage becomes too high, the operation is likely to be unstable and waveform skipping or jitter may be generated. It is recommended that the ripple voltage of the output voltage should be 1% or less of the set output voltage. The ripple voltage of the output voltage is determined as the product of ΔIL and ESR (equivalent series resistance) of the output capacitor, therefore when the ESR is too large, a problem may happen. The ESR should also be taken into account as well as the selection of the output capacitor. Vout ripple = ΔIL x ESR of output capacitor 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 The larger is the inductance, the smaller will be the ripple current/voltage. But the outer size of the coil becomes larger. 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 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 obtained by the equation (1). 10 SI-8000FDL However, it should be noted that the ripple value should also be adjusted to be appropriate. 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 (3.5A) of the SI-8000FDL: output current × 0.1 or so ・In the case that the output current to be used is approximately 2A 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 = 300 KHz, L1 (25 5) 5 ≒ 26.7uH 0.5 25 300 103 As shown above, the coil of about 27μH 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 possible to the regulator IC. Even in the case that the rectifying capacitor of the AC rectifier circuit is located in the input circuit, the input capacitor cannot play a role of the rectifying capacitor unless it is connected close to the SI-8000FDL. The selection of C1 shall be made in consideration of the following points: 11 SI-8000FDL 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 Current Waveform of C1 C1電流波形 VIN 1.VIN Ripple Current ﾘｯﾌﾟﾙ電流 0 Iv Ip C1 Ton D T Ton T 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, 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): Irms 1.2 Vo Io Vin －－(2) For instance, where VIN = 20V, Io = 3A and 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. 12 SI-8000FDL IL Vout L1 C2電流波形 Current Waveform of C2 Io ﾘｯﾌﾟﾙ電流 Ripple Current ESR 0 RL ⊿IL C2 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. The ripple current effective value of the output capacitor is calculated 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 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 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 13 SI-8000FDL parallel with an electrolytic capacitor is effective in reducing the output ripple voltage only when it is used at low temperature (< 0°C). 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 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 SW terminal (pin 2) of the SI-8000FD 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. It is recommended not use the ferrite beads for the flywheel diode. 14 SI-8000FDL ● 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,IN VIN 2.SW VOUT R1 SI-8001FDL 4.ADJ C1 5.Vc 3.GND D1 C2 R2 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 ADJ Terminal (Output Voltage Set-up) The ADJ terminal is a feedback detection terminal for controlling the output voltage. It is recommended to connect it as close as possible to the output capacitor C2. When they are not close, the abnormal oscillation may be caused due to the poor regulation and increase of switching ripple. The output voltage set-up is achieved by connecting R1 and R2. (The IADJ lower limit is 0.8mA, and the upper limit is not defined. However, it is necessary to consider that the consumption current shall increase according to the IADJ value, resulting in lower efficiency.) 15 SI-8000FDL R1, R2 and output voltage are calculated from the following equations: IADJ = VADJ / R2 *VADJ = 0.8v ±2% R1 = (Vo-VADJ) / IADJ R2 = VADJ / IADJ Vout = R1 × (VADJ / R2) + VADJ The layout of voltage detection line should be made in compact form for stable operation in order to avoid the effect of switching IADJ noise. R2 should be connected for the stable operation when set to Vo = 0.8V. It is recommended to set the output voltage to 8% or higher of the input voltage. Constants and variation range are shown in the following table in the case that the output voltage is set for the output voltage setting resistors R1 and R2 by the resistance constants of existing accuracy of 1% and 0.5%. Table of constants for R1/R2 Vo setting SI-8001FFE R1,R2Vo設定定数表 Resistance Constants of Accuracy of 1% Resistance Constants of Accuracy of 0.5% 1%精度抵抗定数での構成 0.5%精度抵抗定数での構成 Target 目標Vout(V) Calculated Accuracy (%) Accuracy (%) R1（Ω ） R2(Ω ） 計算精度(%) R1（Ω ） R2(Ω ） Calculated 計算精度(%) Vout (V) +2.61 +2.26 1.2 402 806 402 806 -2.73 -2.41 +2.72 +2.72 1.8 1000 806 1010 806 -3.48 -2.41 +4.15 +2.64 2.5 1690 787 1690 796 -2.64 -2.73 +2.67 +2.86 3.3 2490 806 2490 796 -4.31 -2.67 +3.50 +2.68 5 4220 806 4170 796 -3.85 -3.00 +3.75 +2.95 9 8250 806 8160 796 -3.89 -2.88 +3.77 +2.58 12 11000 787 11100 796 -3.96 -3.27 +3.25 +3.11 24 23200 806 23400 806 -4.57 -2.84 The wiring of ADJ terminal, R1 and R2 that run parallel to the flywheel diode should be avoided, because switching noise may interfere with the detection voltage to cause abnormal oscillation. It is recommended to implement the wiring from the ADJ terminal to R2 as short as possible. 16 SI-8000FDL Mounting Board Pattern Example Surface Mount Type (SI-8001FDL) 17 SI-8000FDL ● 4-3 Operation Waveform Check It can be checked by the waveform between the pin 2 and 3 (SW - GND) of the SI-8000FDL 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 and C4 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 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. 18 SI-8000FDL ● 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 基 準 電 圧 ESR Reference Voltage -180deg Negative Feedback Loop 負帰還ﾙｰﾌﾟ Load 負荷 C2 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. 1-step Differential Amplifier IN OUT Bode Diagram Example 20dB 0dB 9k 1k -0deg -45deg -90deg Gain ｹﾞｲﾝ 0.1fp Frequency 周波数 Phase 位相 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 19 SI-8000FDL 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 Gain Intersection ｹﾞｲﾝ交点 Frequency 周波数 Frequency 周波数 Phase 位相特性 Characteristics Phase位相余裕 Margin (>0) -180deg Phase Intersection 位相交点 Stable 安定な場合 Phase Intersection 位相交点 -180deg Unstable 不安定な場合 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 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): 20 SI-8000FDL ｆLC 1 2 LC －－－(5) 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 周波数 Frequency 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. 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. 21 SI-8000FDL Phase Characteristics: fpとf LCが近い場合の位相特性 when fp and fLC are close Phase 位相 Phase 位相 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 Amplification 増幅部 Section Amplification 増幅部 Section LCﾌｨﾙﾀ LC Filter LC Filter LCﾌｨﾙﾀ fLC fLC -180deg -180deg Synthesized Characteristics 合成特性 位相遅れ大 Long Phase Delay 位相遅れ小 Short Phase Delay 合成特性 Synthesized Characteristics -180deg -180deg 周波数 Frequency 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 regulator I.C. チョッパーReg ゲイン、位相特性例 60 630 50 540 450 Gain ｹﾞｲﾝ 30 360 20 270 10 180 0 90 -10 -20 0 位相 Phase -90 -30 -40 100 Phase (°) 40 位相（゜） Gain (dB) ｹﾞｲﾝ（dB） Typical Characteristics of Gain and Phase -180 1000 Frequency 周波数 （Hz） -270 10000 (Hz) 22 SI-8000FDL ● 4 - 5 Thermal Design 4-5-1 Calculation of Heat Dissipation for SI-8001FDL In the case of the surface mounting type SI-8001FDL, the heat is dissipated toward the copper foil on the mounting board, therefore the thermal design should be made in consideration of copper foil area, board material and number of copper foil layers. The stem part of the backside of the SI-8001FDL is connected with pin 3 (GND) by the inner frame and heat dissipation performance is improved by taking the larger GND pattern which is directly connected with the stem part. In order to confirm the junction temperature, the temperature of the stem spot shown below should be measured to calculate the temperature by the following equation. Tj = Tc + Pd × 3°C/W * Tc = Actually measured stem temperature Temperature measurement point Junction thermal resistance: 3°C /W Reference data (Copper foil are vs Thermal resistance on single side copper foil board) Glass-epoxy board 40 x 40mm Copper Area (mm2) 23 SI-8000FDL 5. Application ● 5-1 ON / OFF Control of Output Voltage is directly applied to Vc terminal (pin 5) to enable the ON/OFF control of output. When the Vc terminal is open, the operation is in ON state. ● 5-2 Spike Noise Reduction In order to reduce the spike noise, it is possible to compensate the output waveform of the SI-8000FD and the recovery time of the diode by a capacitor, but it should be noted that the efficiency is also slightly reduced. around 10Ω 10Ω 程度 around 1000pF 1000pF程度 2.SW 1.VIN SI-8000FF around 10Ω 10Ω 程度 3.GND around 1000pF 1000pF程度 Without noise reduction circuit With noise reduction circuit A resistor of 10Ω and a capacitor of 2200pF are connected to external resistor * 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. 24 SI-8000FDL ● 5-3 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, such as in battery chargers. SI-8001FD SI-8000S,SS 25 SI-8000FDL 6. Typical Characteristics (1) Efficiency SI-8001F Vo=3.3v SI-8001FFE 効率 Efficiency SI-8001FDL Vo=1.5v 70 90 65 60 Efficiency % Vin=5v Vin=8v Vin=12v Vin=15v 55 50 45 効率 % Efficiency % 効率 % SI-8001FDL 80 75 70 Vin=8v 15v 20v 30v 40v 65 40 0 85 1 2 Iout A 3 60 4 0 0.5 1 3 3.5 2.5 3 3.5 90 85 80 効率 % Vin=5v Vin=8v Vin=12v Vin=15v 75 Vin=8v 15v 20v 30v 40v 70 65 60 1 2 Iout A 3 0 4 0.5 1 1.5 2 Iout A SI-8001F Vo=12v SI-8001FFE 効率 SI-8001FDL SI-8001FDL Vo=2.5v 80 100 75 95 70 90 Vin=5v Vin=8v Vin=12v Vin=15v 65 60 55 効率 % 効率 % 2.5 SI-8001F SI-8001FDL Vo=5v Vo=1.8v 0 効率 % 2 Iout A SI-8001FFE 効率 SI-8001FDL 75 70 65 60 55 50 45 40 1.5 85 Vin=15v 20v 30v 40v 80 75 70 50 0 1 2 Iout A 3 4 0 0.5 1 1.5 2 2.5 3 3.5 Iout A 26 4 SI-8000FDL (2) Rising Low voltage behavior 入力電圧– vs 出力電圧 Input Voltage Output Voltage SI-8001FDL SI-8001FFE Vo=18v設定 Vo=10V 94 6.00 Vin=21v Vin=25v Vin=30v Vin=35v Vin=40v 88 86 Vout 84 出力電圧Vo [V] 90 Voltage Efficiency % Output (V) 92 効率 % Characteristics 82 80 0 1 2 3 5.00 4.00 3.00 Io=0A 0.5A 1A 2A 3.5A 2.00 1.00 0.00 4 0 1 Iout A (3) Load SI-8001FDL Efficiency SI-8001FFE 効率 3 4 5 6 7 Regulation Load regulation ﾛｰﾄﾞレギュレーション Load Regulation Vo=24v 5.1 96 95 94 93 92 91 90 89 88 87 86 5.08 Voltage 出力電圧 Vout [V] Output (V) Efficiency % 効率 % 2 Input 入力電圧VIN Voltage VIN [V] (V) Vout Vin=27v 30v 35v 40v 5.06 5.04 Vin=40v 5.02 Vin=30v 5 Vin=15v 4.98 Vin=10v 4.96 4.94 Vin=8v 4.92 0 1 2 Iout A 3 4 4.9 0 1 2 出力電流 Iout [A] Output Current Iout (A) 3 (4) Quiescent current Quiescent Current 27 8 SI-8000FDL (8) Vc Terminal Control Input Current (5) Circuit Consumption Current at Off Vc Terminal Input Current Quiescent Current (uA) Vc Terminal Control Input Voltage (V) Input Voltage VIN (V) (6) Over Current Protection 6 Output Voltgae VO (V) 5 VIN=8V 4 VIN=15V 3 VIN=30V VIN=40V 2 1 0 1 2 3 4 5 Output Current Io (A) (7) Thermal Protection 過熱保護特性 Thermal Protection 6.00 出力電圧Vo [V] Output Voltgae VO (V) 5.00 4.00 VIN=15V, Io=10mA 3.00 2.00 1.00 0.00 0 20 40 60 80 100 120 140 160 180 接合部温度Tｊ [℃] Junction Temperature (℃) 28 SI-8000FDL 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 widthis 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. 29 SI-8000FDL 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. 30