SI-8005Q/SI-8105QL Application Note Full Mold Type Chopper Type Switching Regulator IC SI-8005Q/SI-8105QL Series April 2009 Rev.4.0 SANKEN ELECTRIC CO., LTD. SI-8005Q/SI-8105QL －－－ Contents －－－ 1. General Description 1-1 Features －－－－－－－－－－ 3 1-2 Applications －－－－－－－－－－ 3 1-3 Type －－－－－－－－－－ 3 2-1 Package Information －－－－－－－－－－ 4 2-2 Ratings －－－－－－－－－－ 6 2-3 Circuit Diagram －－－－－－－－－－ 8 3-1 Terminal List －－－－－－－－－－ 9 3-2 Functional Description of Terminal －－－－－－－－－－ 9 4-1 PWM Output Voltage Control －－－－－－－－－－ 10 4-2 Overcurrent Protection / Thermal Shutdown －－－－－－－－－－ 11 5-1 External Components －－－－－－－－－－ 13 5-2 Pattern Design Notes －－－－－－－－－－ 20 5-3 Power Supply Stability －－－－－－－－－－ 22 5-4 Power Dissipation of IC with No load －－－－－－－－－－ 22 6-1 Soft Start －－－－－－－－－－ 24 6-2 Output ON / OFF Control －－－－－－－－－－ 25 6-3 Spike Noise Reduction －－－－－－－－－－ 25 6-4 Switching Terminal Negative Potential －－－－－－－－－－ 26 6-5 Reverse Bias Protection －－－－－－－－－－ 26 6-6 LED Series Connection －－－－－－－－－－ 27 －－－－－－－－－－ 30 2. Specification 3. Terminal Description 4. Operational Description 5. Cautions 6. Applications 7. Terminology 2 SI-8005Q/SI-8105QL 1. General Description The SI-8005Q is a buck switching regulator IC with a built-in power MOS. Due to a current control system, it is applicable to such a super low ESR capacitor as a ceramic capacitor. It is provided with various protection functions such as overcurrent protection, low input prohibition, overheat protection etc. In order to protect the IC against in-rush current at start-up, the soft start function is provided. The soft start time can be set by connecting external capacitors. A function to turn on/off external signals is also provided and by sending external signal to the EN terminal, the SI-8105Q can be turned on/off. This device is supplied in the small and thin type HSOP 8-pin package including a heat slag on the backside. The SI-8105QL is mounted in the DIP 8-pin package for flow mounting /power supply board (single side surface board). ● 1-1 Features - Output current 3.5A The output current of each output is maximum 3.5A in the HSOP 8-pin surface mounting package. - High efficiency Maximum efficiency 94% (VIN = 8V / Vo = 5V / Io = 0.8A) - Output voltage variable: 0.5 - 24V - Low ESR capacitor for output The ceramic capacitor can be used. - Operating frequency: 500kHz - 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 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. - ON/OFF function - Small package (SI-8005Q) HSOP8 pin package with small heat slug ● 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 SI-8005Q/SI-8105QL 2. Specification ● 2-1 Package Information 2-1-1 SI-8005Q Unit: mm *1 Type number *2 Lot number (three digit) 1st letter: The last digit of year 2nd letter: Month 1 to 9 for Jan. to Sep. O for Oct. Pin Assignment 1. BS 2. IN 3. SW N for Nov. D for Dec. 3rd and 4th letter: week *3 Control number (four digit) 4. GND 5. FB 6. COMP External Terminal Processing: Sn plating 7. EN 8. SS 4 SI-8005Q/SI-8105QL 2-1-2 SI-8105QL Unit: mm *1 Type number *2 Lot number (three digit) 1st letter: The last digit of year 2nd letter: Month 1 to 9 for Jan. to Sep. O for Oct. N for Nov. D for Dec. 3rd and 4th letter: week *3 Control number (four digit) Pin Assignment 1. BS 2. IN 3. SW 4. GND 5. FB 6. COMP 7. EN 8. SS External Terminal Processing: Sn-Ag plating 5 SI-8005Q/SI-8105QL ● 2-2 Ratings Table 1 Absolute Maximum Ratings Parameter Symbol Rating Unit Input Voltage VIN VIN 30 V Input Voltage VEN VEN 6 V 1.35 Allowable Power Dissipation (8005Q) *2 Pd *1 W 1.50 (8105QL) *3 Junction Temperature Tj 150 °C Storage Temperature Tstg -40～150 °C Thermal resistance (Junction and case) Thermal resistance (Junction and ambient) Conditions 40 θj-c (8005Q) *2 °C/W 25 (8105QL) *3 74 θj-a (8005Q) *2 °C/W 67 (8105QL) *3 *1. Since the thermal shutdown is provided, it may be operated at Tj > 140°C. *2. Glass epoxy board: 30.0mm × 30.0mm (copper foil area: 25.0mm × 25.0mm) *3. Glass epoxy board: 70.0mm × 60.0mm (copper foil area: 1310 mm2) Table 2 Recommended Conditions Parameter Symbol SI-8005Q/SI-8105QL DC Input Voltage VIN Output Current IO 0～3.5 A Junction Temperature in Operation Tjop -30 - +125 °C Temperature in Operation Top -30 - +85 °C *2 Vo+3v - 28 Unit V *2 The minimum value of input voltage range is 4.75V or VO + 3V whichever higher. In the case of VIN = Vo+2 ~ Vo+3, IOUT is equal to 2A MAX. In the case that the IC is used at VIN = Vo +1 – Vo +2V (especially in the case that VIN voltage is 8V or lower), IC loss will be increased, therefore efficient heat dissipation is required in designing the wiring board. When sufficient heat dissipation cannot be obtained because of several limitations with respect to the size of wiring boards, mounted component etc, the overheat protection operation will function. 6 SI-8005Q/SI-8105QL Table 3 Electrical Characteristics (Ta = 25°C, Vo = 5V, R1 = 46kΩ, R2 = 5.1kΩ) Ratings Parameter Setting Reference Voltage Output Voltage Temperature Unit Symbol VREF Test Condition MIN MIN MIN 0.485 0.500 0.515 ΔVREF/ΔT ±0.05 V mV/°C Coefficient VIN=12V, IO=1.0A VIN=12V, IO=1.0A Ta=-25°C to 100°C Efficiency *8 η Operation Frequency (SI-8005Q) fo 450 500 Operation Frequency (SI-8105QL) fo 315 90 % VIN=12V, Vo=5V, IO=1A 550 kHz VIN=16V, Vo=5V, IO=1A 350 385 kHz VIN=16V, Vo=5V, IO=1A VIN=8~28V, Vo=5V, IO=1A Line Regulation VLine 10 60 mV Load Regulation VLoad 10 60 mV VIN=12V,Vo=5V, IO=0.1 - 3.5A Overcurrent Protection Start Current IS Circuit Current in Non-operation 1 IIN 3.6 6.0 18 A mA VIN=12V, Vo=5V VIN= 12V, VO=5V, IO=0A, VEN= open Circuit Current in Non-operation 2 IIN(off) 10 30 uA VIN= 12V, VO=5V, IO=0A, VEN= 0V Flow-out Current SS terminal at Low Level ISSL 5 μA VSSL=0V, VIN= 16V V VIN=12V V VIN=12V μA VEN=0V Voltage EN terminal High Level Voltage VC/EH Low Level Voltage VC/EL 2.8 2.0 Flow-out Current at Low Level IC/EH 1 Voltage Slope Compensation Kc A/μsec 0.3 Error Amplifier Voltage Gain AEA 1000 V/V Error Amplifier Trans-conductance GEA 800 uA/V Current Sense Amplifier Impedance 1/GCS 0.35 V/A Maximum ON Duty DMAX 90 % Minimum ON Duty DMIN 100 nsec Ron1 180 mΩ VIN<10V Ron2 130 mΩ VIN≧10V High-side Switching ON resistance 7 SI-8005Q/SI-8105QL ● 2-3 Circuit Diagram 2-3-1 Internal Equivalent Circuit VIN SI-8000Q/SI-8105QL 2 IN 5v_ldo P.REG VREF 7 ３ Current Sense Amp OCP Σ３ OSC C1 ５ Boot REG ６ 1 BS C4 0.5V DRIVE PWM LOGIC EN ON/ OFF ３ ４ ４ OVP TSD L1 3 VO SW 5v_ldo C2 D1 ３ R1 COMP 6 ８ 0.5V ７ FB Amp C3 5 UVLO R3 R2 GND １ １ 4 SS 8 C5 Fig. 1 2-3-2 Typical Connection Diagram 1 2 IN 7 C4 BS SW EN 8 C1 IIN IEN SI-8005Q/ SI-8105QL SS FB 4 VIN VEN D1 ISS GND L1 3 R1 COMP IO C2 5 VFB R2 VO RL 6 C3 VSS R3 C1:22μ F/50V C2:47μ F/25V C3:220pF (SI-8005Q) 1200pF(SI-8105QL) D1:SPB-G56S L1:10μ H(SI-8005Q) 22μ H(SI-8105QL) R１:46kΩ R2:5.1kΩ R3:62kΩ (SI-8005Q) 20kΩ (SI-8105QL) C4:10nF/25V Fig. 2 8 SI-8005Q/SI-8105QL 3. Terminal Description ● 3-1 Terminal List Table 4 SI-8005Q/8105QL Terminal Symbol Description 1 BS High side boost terminal 2 VIN Input terminal 3 SW Switching output terminal 4 GND Ground terminal 5 FB Feedback voltage terminal 6 COMP Phase compensation terminal 7 EN ON/OFF terminal 8 SS Soft start terminal ● 3-2 Functional Description of Terminal - BS (terminal No. 1) It is an internal power supply for driving the gate of high side switch Nch - MOS. A capacitor of 10 nF or more is connected between the SW terminal and BS terminal to drive the high side Nch - MOS. - VIN (terminal No. 2) It is an input voltage of IC. - SW (terminal No. 3) It is a switching output terminal which supplies power to the output. - GND (terminal No. 4) It is a ground terminal. - FB (terminal No. 5) It is a terminal for setting the output voltage. The output voltage is set by R1 and R2. - Comp (terminal No. 6) It is a phase compensation terminal for controlling the loop stably. - EN (terminal No. 7) It is a terminal for turning ON/OFF the IC. - SS (terminal No. 8 ) The soft start of output voltage can be made by connecting a capacitor to this terminal. 9 SI-8005Q/SI-8105QL 4. Operational Description ● 4-1 PWM Output Voltage Control The SI-8005Q/8105Q consists of 2 systems of feedback loops of current control and voltage control and 3 blocks which compensate slope and, in the voltage control feedback, the output voltage is fed back for PWM control loop and the SI-8005Q is composed of an error amplifier which compares the division of resistance with the reference voltage of 0.5V. The current control feedback is a loop which feeds back the inductor current for PWM control and the inductor current shunted by using a sense MOS is detected by a current sense amplifier. With respect to the slope compensation, in consideration of current control system, in order to avoid the sub harmonic oscillation, slope compensation is made for the current control slope. As shown in Fig.5, in the SI-8005Q, by means of voltage control feedback, current control feedback and calculation of slope compensation, the PWM control by current control system is made. VIN 2 ５ IN OSC Σ３ Current Sense Amp Boot REG ６ S PWM LOGIC R 1 BS C4 M1 DRIVE ４ ４ L1 3 SW Erramp D1 VO R1 M2 R2 基準電圧0.5V FB ８ 5 Fig.3 Current Control PWM Chopper Regulator Basic Configuration Since the SI-8005Q is a current control regulator, the COMP terminal voltage is proportional to the peak value of the inductor current. When the ULVO is released or the EN terminal exceeds the threshold value, the switching operation is made. At first, switching operation is made by MIN ON duty or MAX ON duty and the high side switch (hereinafter called as M1) and the switch for BS capacitor charging (hereinafter called as M2) turn ON and OFF alternately. M1 is a switching MOS which provides power to the output, while M2 charges the capacitor C4 for boost which drives M1. At M1: ON / M2: OFF, inductor current is increased by applying voltage to the SW switch and inductor, and the output of the current detection amplifier which detects it also rises. The signal to which the output of this current detection amplifier and the Ramp compensation signal are added is compared with the output of the error amplifier by the current comparator (CUR COMP). When the added signal exceeds the output of the error amplifier (COMP terminal voltage), the output of the current comparator becomes “H” to reset the RS flip-flop. Then, M1 turns off and M2 turns on. Thereby, the regenerated current flows through the external SBD (D1). 10 SI-8005Q/SI-8105QL In the SI-8005Q, the reset signal is generated at each cycle to reset the RS flip-flop. In the case the added signal does not exceed the COMP terminal voltage, the RS flip-flop is reset without fail by the signal of the 10% OFF Duty circuit. ● 4-2 Overcurrent Protection / Thermal Shutdown 過電流保護特性 voltageVVo[V] Output 出力電圧 O [V] 6 5 4 As Vo drops, the oscillating frequency 3 is lowered. 2 1 0 0 1 2 3 4 5 6 出力電流 I o[A] Output Current IO [A] Fig.4 Output Voltage Characteristics in Overcurrent The SI-8005Q/8105QL 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 the switching frequency to about 50 KHz. When the overcurrent condition is released, the output voltage will be automatically restored. 出力電圧 Output Voltage Restoration Setting 復帰設定温度 Temperature Protection Setting Temperature 保護設定温度 接合温度 Junction Temperature Fig.5 Output Voltage Characteristics in Thermal Shutdown The thermal shutdown circuit detects the semiconductor junction temperature of the IC and when the junction temperature exceeds the set value (around 140°C), the output transistor is stopped and the output is 11 SI-8005Q/SI-8105QL turned OFF. When the junction temperature drops from the set value for overheat protection by around 10°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. 12 SI-8005Q/SI-8105QL 5. Cautions ● 5-1 External Components 5-1-1 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) For the peak detection current control, the inductance current may fluctuate at the cycle of integral multiple of switching operation frequency. Such phenomenon is called as sub harmonic oscillation and it may theoritically occur in the peak detection current control mode. Therefore, in order to assure stable operation, the inductance current is compensated inside the IC, and it is required to select a proper inductance value to the output voltage. Inductance L Inductance L [uH] Selectable area Please set the L value, however, as the upper limit of ΔIL > 0.1A Output voltage VO [V] Fig. 6 shows the selection range of the inductance L value to avoid the sub harmonic oscillation. The pulse current of choke coil ΔIL and the peak current ILp are expressed by the following equation: IL (Vin Vout ) Vout －－－（A） L Vin f 13 SI-8005Q/SI-8105QL ILp IL Iout 2 －－－（B） From this equation, you will see that as the inductance L of choke coil is decreased, ΔIL and ILP are increased. In the event that the inductance is too small, the fluctuation of choke coil current is larger, resulting in unstable operation of the regulator. Care should be taken of decrease of inductance of choke coil due to magnetic saturation of overload, load short circuit etc. High inductance Low inductance Fig.7 Relation between Ripple current ILP and Output Current IO 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 connected as close as 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 near the SI-8005Q. The selection of C1 shall be made in consideration of the following points: a) The requirement of withstand voltage shall be met. 14 SI-8005Q/SI-8105QL b) The requirement of the allowable ripple voltage shall be met. IIN C1電流波形 VIN 1.VIN Ripple Current ﾘｯﾌﾟﾙ電流 0 Iv Ip C1 Ton T Fig.8 Current Flow of C1 D Ton T Fig. 9 Current Waveform of C1 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. 5-1-3 Output Capacitor C2 The current control system is a voltage control system to which a loop which detects and feeds back the inductance current is added. By adding inductor current to the feedback loop, stable operation is realized without taking into consideration the influence of secondary delay of the LC filter. Therefore, the capacitance C of the LC filter which is required to compensate the secondary delay can be decreased and furthermore, stable operation can be obtained, even if the low ESR capacitor (ceramic capacitor) is used. 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. 15 SI-8005Q/SI-8105QL IL Vout L1 Ripple current ﾘｯﾌﾟﾙ電流 C2電流波形 Io ESR 0 RL ⊿IL C2 Fig.10 C2 current flow Fig.11 C2 current curve 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 －－－(3) 2 3 When ΔIL = 0.5A, Irms 0.5 2 3 ≒ 0.14 A 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 C 2ESR －－－(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, C 2esr 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. 5-1-4 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. 16 SI-8005Q/SI-8105QL In addition, since the output voltage from the SW terminal (pin 3) of the SI-8000Q 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 to use the ferrite bead for the flywheel diode. 5-1-5 Phase compensation elements C3, C6, R3 The stability and responsiveness of the loop are controlled through the COMP terminal. The COMP terminal is an output of the internal trans-conductance amplifier. The series combination of a capacitor and resistor sets the combination of pole and zero which determines characteristics of the control system. The DC gain of voltage feedback loop can be calculated by the following equation: Adc Rl Gcs AEA VFB Vout Here, VFB is feedback voltage (0.5V). AEA is the voltage gain of error amplifier, GCS trans-inductance of current detection and R1 a load resistance value. There are 2 important poles. One is produced by a phase compensation capacitor (C3) and an output resistor of the error amplifier. Another one is produced by a output capacitor and a load resistor. These poles appear at the following frequencies: GEA 2 C 3 AEA 1 fp 2 2 C 2 Rl fp1 Here, GEA is the trans-conductance of error amplifier. In this system, one zero is important. This zero is produced by phase compensation capacitor C3 and phase compensation resistance R3. This zero appears in the following frequencies: fz1 1 2 C 3 R3 If the output capacitor is large and/or ESR is large, this system may have another important zero. This zero is produced by the ESR and capacitance of the output capacitor. And it exists in the following frequencies: fESR 1 2 C 2 RESR In this case, the third pole which is set by the phase compensation capacitor (C6) and phase compensation resistor (R3) is used to compensate the effect of ESR zero on the loop gain. This pole exists in the following frequencies: p3 1 2 C 6 R3 The objective of design of phase compensation is to form the converter transfer function to obtain the desired loop gain. The system crossover frequency where the feedback loop has a single gain is important. The lower crossover frequency will produce the slower line and load transient. In the meantime, the higher crossover frequency may cause instability of the system. The selection of the most suitable phase 17 SI-8005Q/SI-8105QL compensation element is described below. 1. A phase compensation resistor (R3) is selected to set the resistor at the desired crossover frequency. The calculation of R3 is made by the following equation: R3 2 C 2 fc Vout 2 C 2 0.1 fs Vout GEA GCS VFB GEA GCS VFB Here, fc is a desired crossover frequency. It should be one tenth or lower of the normal switching frequency (fs). 2. In order to achieve the desired phase margin, a phase compensation capacitor (C3) is selected. For the application having a representative inductance value, adequate phase margin is provided by setting the zero compensation of one fourth or lower of the crossover frequency. C3 is calculated by the following equation. C3 4 2 R3 fc R3 is a phase compensation resistor. 3. It is required to judge whether the second compensation capacitor C6 is necessary or not. It will be necessary, when the ESR zero of the output capacitor is located at a frequency which is lower than the half of the switching frequency. Namely, it is necessary, when the following equation is applicable. 1 fs 2 C 2 RESR 2 In this case, the second compensation capacitor C6 is added and the frequency fp3 of ESR zero is set. C6 is calculated from the following equation. C6 C 2 RESR R3 The constants for each output setting voltage in the case that ceramic capacitors or aluminum electrolytic capacitors are used are shown in the following table. The inductor L should be selected by reference to the choke coil L1 of 4-1-1. 18 SI-8005Q/SI-8105QL Table 5 Output setting voltage (use ceramic capacitors) fc = 50kHz Vout L Cout [uF] [V] [uH] (ceramic capacitor) fc = 20kHz R3 C3 C6 R3 C3 C6 [kΩ] [pF] [pF] [kΩ] [pF] [pF] 1.2 2.4~10 22 x 2 14 1000 No 5.7 5600 No 1.8 4.7~10 22 x 2 20 620 No 8.5 3800 No 3.3 6.8~ 22 x 2 39 360 No 15 2200 No 5 8.2~ 22 x 2 59 220 No 20 1500 No 12 22~ 22 x 2 140 100 No 57 620 No Table 6 Output setting voltage (use aluminum electrolytic capacitors) Vout L [V] [uH] Cout [uF]/ fc = 50kHz ESR[mΩ] R3 C3 C6 R3 C3 C6 [kΩ] [pF] [pF] [kΩ] [pF] [pF] (aluminum electrolytic capacitor) fc = 20kHz 1.2 2.4~10 220/100 70 180 330 28 1200 860 1.8 4.7~10 220/100 100 180 320 42 820 560 3.3 6.8~ 220/100 190 100 150 78 560 330 5 8.2~ 220/100 290 100 100 110 330 220 12 22~ 220/100 700 100 100 280 120 100 Table 7 Output setting voltage (use ceramic capacitors) (SI-8105QL) fc = 35kHz Vout L Cout [uF] [V] [uH] (ceramic capacitor) fc = 14kHz R3 C3 C6 R3 C3 C6 [kΩ] [pF] [pF] [kΩ] [pF] [pF] 1.2 2.4~10 22 x 2 10 2200 no 4 10000 No 1.8 4.7~10 22 x 2 15 1800 No 6 8600 No 3.3 6.8~ 22 x 2 27 680 No 10 4700 No 5 8.2~ 22 x 2 40 470 No 16 3300 No 12 22~ 22 x 2 100 220 No 40 1200 No 19 SI-8005Q/SI-8105QL Table 8 Output setting voltage (use aluminum electrolytic capacitors) (SI-8105QL) Vout L [V] [uH] Cout[uF]/ fc = 35kHz ESR[mΩ] R3 C3 C6 R3 C3 C6 [kΩ] [pF] [pF] [kΩ] [pF] [pF] (aluminum electrolytic capacitors) fc = 14kHz 1.2 2.4~10 220/100 50 390 470 20 3300 1500 1.8 4.7~10 220/100 75 330 330 30 1800 1000 3.3 6.8~ 220/100 130 220 220 56 1000 470 5 8.2~ 220/100 200 100 150 83 560 330 12 22~ 220/100 500 100 100 200 330 180 ● 5-2 Pattern Design Notes 5-2-1 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. VIN 2 1 BS IN 7 EN C4 SI-8000Q R1 C1 8 C5 FB COMP 6 GND 4 C3 C6 OPEN GND SS VO L1 SW 3 VFB 5 C2 D1 R2 IADJ R3 GND 5-2-2 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 20 SI-8005Q/SI-8105QL 5-2-3 FB Terminal (Output Voltage Set-up) The FB 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. IFB should be set to be around 0.1mA. (The IFB lower limit is 0.1mA, and the upper limit is not defined. However, it is necessary to consider that the consumption current shall increase according to the IFB value, resulting in lower efficiency.) R1, R2 and output voltage are calculated from the following equations: IFB = VFB / R2 *VFB = 0.5V ±3% R1 = (Vo – VFB) / IFB R2 = VFB / IFB Vout = R1 × (VFB / R2) + VFB - R2 should be connected for the stable operation when set to Vo = 0.5V. - It is recommended to set the output voltage to 10% or higher of the input voltage The wiring of COMP terminal, FB 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 FB terminal to R2 as short as possible. - Mounting Board Pattern Example Component Insertion Type (SI-8005Q) Front side: materials on this side Back side: GND side 21 SI-8005Q/SI-8105QL Component Insertion Type (SI-8105QL) Silk printed side ● 5-3 Power Supply Stability The phase characteristics of the chopper type regulator are synthesized by the phase characteristics inside the regulator IC and that of output capacitor Cout and the load resistor Rout. 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, external parts such as resistors and capacitors should be connected outside the IC for phase compensation. Please refer to phase compensation elements C3, C6 and R3 of 4-1-5. ● 5-4 Power Dissipation of IC with No Load 5-4-1 SI-8005Q Power dissipation of IC (2) Power dissipation with load 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 VIN=12V,28V, Io=0A L=10μH, Ta=25°C VIN=28V VIN=12V 0 5 10 15 20 出力電圧[V] Output Voltage[V] Output Voltage 25 30 損失[W] dissipation [W] PowerDissipation Power 損失[W] dissipation Power Dissipation[W] Power (1) Power dissipation with no load 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 VIN=28V, L=10μH, Ta=25°C VIN=12V Vo=6V 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 出力電流[A] Peak voltage: Output Current-3.0V Output Current [A] 22 1.6 SI-8005Q/SI-8105QL 5-4-2 SI-8105QL Power dissipation of IC (2) Power dissipation with load VIN=12V,28V, Io=0A L=22μH, Ta=25°C VIN=28V 0.8 0.6 0.4 VIN=12V 0.2 0 0 5 10 15 20 出力電圧[V] Output [V] Outputvoltage Voltage 25 30 Power Dissipation 1 Dissipation [W] Power損失[W] 損失[W] Power Dissipation Power Dissipation [W] (1) Power dissipation with no load 1.0 VIN=28V, L=22μH, Ta=25°C 0.8 0.6 VIN=28V Vo=12V 0.4 0.2 VIN=12V Vo=6V 0.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 出力電流[A] Output current [A] Output Current The SI-8105Q/8105QL have such architecture that the energy of the output capacitor C2 is consumed by the LS SW MOS in the internal equivalent circuit diagram of Fig. 1, therefore loss in the IC will occur. (Refer to (2) Power dissipation with load.) 23 1.6 SI-8005Q/SI-8105QL 6. Applications ● 6-1 Soft Start When a capacitor is connected to terminal 8, the soft start is activated when the input voltage is applied. Vout rises in relation with the charging voltage of Css. Therefore, the rough estimation is done by the time constant calculation of Css charging. The capacitor Css controls the rise time by controlling the OFF period of PWM control. The rise time tss is calculated approximately by the following equation: The terminal 8 should be open, when the soft start is not used. tss = (Css × Vss) / IssL (sec) The time that output voltage rises to set-up value is equal with the time that Vss rises to 0.5V. The variation range of each parameter Vss = 0.5V ±3% (0.485 – 0.515V) Vss and Iss are parameters of soft start time variation. Iss = 5μA ±30% (3.5 – 6.5μA) Variation range can be calculated with following equations. When Css = 0.47μF, tOUT min = Css × Vss min / Iss max = 0.47μF × 0.485V / 6.5μA = 37.2msec tOUT typ = Css × Vss / Iss = 0.47μF × 0.5V / 5μA = 47msec tOUT max = Css × Vss min / Iss max = 0.47μF × 0.515V / 3.5μA = 69.1msec 24 SI-8005Q/SI-8105QL Since the SS terminal is pulled up (4.7V TYP) with the internal power supply of IC, the external voltage can not be applied. If there is no Css or it is extremely low, Vout rises at the time constants charging the output capacitor with the output current restricted by the overcurrent protection Is. Time constants at output capacitor start-up t = (Co × Vo) / Is (at no load) *The amount of load current is deducted from the Is value at load. ● 6-2 Output ON/ OFF Control The output ON-Off control is possible using the SS (No.7) terminal. The output is turned OFF when the terminal 7 voltage falls below VENL (2.0V) by such as open collector. A voltage dividing resistor should be inserted between VIN and GND and divided VIN voltage can be applied to the EN terminal. Over 6V shall not be applied to EN terminal. 2.VIN SI-8005Q SI-8005Q 7.EN 7.EN ● 6-3 Spike Noise Reduction In order to reduce the spike noise, it is possible to compensate the output waveform of the SI-8005Q and the recovery time of the diode by a capacitor, but it should be noted that the efficiency is also slightly reduced. Around 10Ω Around 1000pF 25 SI-8005Q/SI-8105QL * 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. ● 6-4 SW terminal negative potential The assurance of SW terminal negative electric potential shall be as follows: Assured value: within 30V of voltage difference between VIN and VS, Peak voltage of SW terminal negative potential: -3.0V / hour: shall not exceed 100 nsec. Peak voltage: -3.0V Time: 100nsec ● 6-5 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. 2PIN SI-8005Q 3PIN 26 SI-8005Q/SI-8105QL ● 6-6 LED Series Connection The LED is efficiently operated by its constant current driving system without unevenness of luminance. The current consumption can be reduced due to the EN function at shut down and the light dimming of constant LED current can be made by inputting PWM signal. - Application circuit diagram Circled numbers mean Pin no. on IC. - Characteristics of efficiency 27 SI-8005Q/SI-8105QL - Bill of materials symbol Spec. Description C1 10μF (BV 50V) Input capacitor C2 10μF (BV 50V) Input capacitor C4 22μF (BV 16V) Output capacitor C5 22μF (BV 16V) Output capacitor C7 10nF (BV 50V) Booster capacitor C8 560pF (BV 50V) For Phase compensation (3LEDs) R3 0.5Ω (1W) For Current detection R4 46.4kΩ (0.5W) For Phase compensation (3LEDs) C10 1.5MΩ (0.5W) For Soft start Capacitor Resistor (changed to resistor for quick response) - Diode Di 60V/5A Flywheel diode Coil L1 10uH Choke coil Constant for phase compensation LEDs - Cout[uF] (ceramic capacitor) R4 [kΩ] C8 [pF] 3 22 × 2 46.4 560 4 22 × 2 69.8 470 6 22 × 2 100 360 PWM dimming PWM light dimming can be made by inputting signals into the EN terminal by an oscillator etc. Switching curve of IC LED current curve Output voltage curve Pulse signal curve of EN When pulse signals are inputted into the EN terminal, the application voltage of pulse signals should be 3 28 SI-8005Q/SI-8105QL 5V and the frequency 100 - 300Hz. - LED current The LED current varies subject to duty ratio. Condition: LED: 4 series (application of 100Hz, 5V from the EN terminal) When pulse signals are inputted into the EN terminal, the applied voltage and frequency should be 3 - 5V and 100 - 300Hz respectively. 29 SI-8005Q/SI-8105QL 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. 30 SI-8005Q/SI-8105QL 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. 31