NR111D

31 V, Buck Converter NR111D Data Sheet Description Package The NR111D is a buck converter IC that integrates the power MOSFET. With the current mode control, ultra low ESR capacitors such as ceramic capacitors can be used. The IC has protection functions such as Overcurrent Protection (OCP), Undervoltage Lockout (UVLO) and Thermal Shutdown (TSD). An adjustable Soft-start by an external capacitor prevents the excessive inrush current in startup. The feature increasing efficiency at light loads allows the device to be used in the energy-saving applications. The IC integrates phase compensation circuit which reduces the number of external components and simplifies the design of customer application. The IC has the EN pin that turns the regulator on or off, and achieves low power consumption requirements. The package of NR111D is the DIP8. DIP8 Not to scale Specification ● ● ● ● Input Voltage, VIN = 8 V to 31 V Output Voltage, VO = 0.8 V to 24 V Maximum Output Current, IO = 4 A Operation Frequency: 350 kHz Application Features ● Up to 94% Efficiency Up to 68% Efficiency at Maximum at Light Load (IO = 20 mA) ● Current mode PWM control ● Stable with Low ESR Ceramic Output Capacitors ● No External Components Required by Incorporating Phase Compensation ● Soft-start Function Adjustable Soft-start time with an External Capacitor ● External ON/OFF Function ● Protection Functions: Overcurrent Protection (OCP): Drooping, auto-restart Thermal Shutdown (TSD): Auto-restart Undervoltage Lockout (UVLO) ● AV Equipment ● White Goods ● Power Supply for Digital Appliances Typical Application R3 R1 NR111D 1 BS SS 8 2 IN EN 7 C10 3 SW 4 GND VIN ISET 6 FB 5 L1 VOUT R5 C1 C2 C9 D1 C4 C5 R4 R6 GND GND NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 1 NR111D Contents Description ------------------------------------------------------------------------------------------------------ 1 Contents --------------------------------------------------------------------------------------------------------- 2 1. Absolute Maximum Ratings----------------------------------------------------------------------------- 3 2. Recommended Operating Conditions ----------------------------------------------------------------- 3 3. Electrical Characteristics -------------------------------------------------------------------------------- 4 4. Typical Performance Characteristics ----------------------------------------------------------------- 5 5. Block Diagram --------------------------------------------------------------------------------------------- 7 6. Pin Configuration Definitions --------------------------------------------------------------------------- 7 7. Typical Application --------------------------------------------------------------------------------------- 8 8. Physical Dimensions -------------------------------------------------------------------------------------- 9 9. Marking Diagram --------------------------------------------------------------------------------------- 10 10. Operational Description ------------------------------------------------------------------------------- 11 10.1. PWM Output Control ---------------------------------------------------------------------------- 11 10.2. Soft Start Function -------------------------------------------------------------------------------- 12 10.3. External ON/OFF Function --------------------------------------------------------------------- 12 10.4. Overcurrent Protection -------------------------------------------------------------------------- 13 10.5. Thermal Shutdown -------------------------------------------------------------------------------- 13 11. Design Notes ---------------------------------------------------------------------------------------------- 14 11.1. External Components ---------------------------------------------------------------------------- 14 11.1.1. Choke Coil, L1 ------------------------------------------------------------------------------- 14 11.1.2. Input Capacitor, CIN ------------------------------------------------------------------------ 15 11.1.3. Output Capacitor, COUT -------------------------------------------------------------------- 15 11.1.4. Freewheel Diode, D1 ------------------------------------------------------------------------ 16 11.1.5. Output Voltage, VO, and Output Capacitor -------------------------------------------- 17 11.2. Allowable power dissipation -------------------------------------------------------------------- 17 11.2.1. Power Supply Stability --------------------------------------------------------------------- 17 11.2.2. Spike Noise Reduction ---------------------------------------------------------------------- 17 11.2.3. Reverse Bias Condition --------------------------------------------------------------------- 18 11.3. Pattern Layout ------------------------------------------------------------------------------------- 19 11.3.1. Large Current Trace ----------------------------------------------------------------------- 19 11.3.2. Input and Output Capacitor -------------------------------------------------------------- 19 11.3.3. FB Pin Setting (Output Voltage Setting) ------------------------------------------------ 19 12. Pattern Layout Example ------------------------------------------------------------------------------- 20 Important Notes ---------------------------------------------------------------------------------------------- 22 NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 2 NR111D 1. Absolute Maximum Ratings Unless otherwise specified, TA = 25 °C. Parameter Symbol Conditions Rating Unit DC Input Voltage VIN 35 V BS Pin Voltage VBS 44 V BS–SW Voltage VBS-SW SW Pin Voltage VSW 35 V FB Pin Voltage VFB 5.5 V EN Pin Voltage VEN 35 V SS Pin Voltage VSS 5.5 V 1.47 W DC 8 Pulse width ≤ 30ns 12 The IC is mounted on the glass-epoxy board (70 mm × 60 mm) with copper area (1310 mm2) TJ(MAX) = 150 °C V Power Dissipation (1) PD Junction Temperature (2) TJ −40 to 150 °C TSTG −40 to 150 °C θJP 41 °C/W 85 °C/W Storage Temperature Thermal Resistance (junction–GND Pin) Thermal Resistance (junction–ambient air) (1) (2) 2. θJA The IC is mounted on the glass-epoxy board (70 mm × 60 mm) with copper area (1310 mm2) Remarks Limited by thermal shutdown. The temperature detection of thermal shutdown is about 160 °C. Recommended Operating Conditions Parameter Symbol DC Input Voltage (1) DC Output Current Output Voltage Ambient Operating Temperature (3) (2)(3) Conditions Ratings Units Min. Max. VIN 6.5 31 V IO 0 4.0 A VO 0.8 24 V TOP −40 85 °C Remarks (1) The minimum value of input voltage is taken as the larger one of either 6.5 V or VO +3 V. See Typical Application Circuit for recommended circuit. (3) To be used within the allowable package power dissipation characteristics. (2) NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 3 NR111D 3. Electrical Characteristics Unless otherwise specified, TA = 25 °C. Parameter Symbol Reference Voltage Conditions Min. Typ. Max. Unit 0.784 0.800 0.816 V ― ±0.05 ― mV/°C −20% 350 20% kHz VIN = 8 V to 30 V, VO = 5 V, IO = 1.0 A ― 50 ― mV VIN = 12 V, VO = 5 V, IO = 0.1 A to 2.0 A VIN = 12 V, VO = 5 V, ISET = GND VIN = 12 V, VO = 5 V, IO = 0 A VIN = 12 V, VO = 5 V, IO = 0 A, VEN = 0 V ― 50 ― mV ― 5.5 ― A ― 1.0 ― mA ― 1.0 ― μA VSS = 0 V, VIN = 12 V 6 10 14 μA IEN VEN = 10 V ― 20 50 μA VEN VIN = 12 V 0.7 1.4 2.1 V ― 90 ― % ― 150 ― ns 151 165 ― °C ― 20 ― °C ― 105 ― mΩ VREF Output Voltage Temperature Coefficient Switching Frequency VIN = 12 V, IO = 1.0 A VIN = 12 V, IO = 1.0 A, ΔVREF/ΔT −40 °C to 85 °C VIN = 12 V, VO = 5 V, fOSC IO = 1.0 A Line Regulation (4) VLine Load Regulation (4) VLoad Overcurrent Protection Threshold IS Supply Current IIN Shutdown Supply Current Source current at Low Level Voltage Sink Current EN Pin Threshold Voltage Max On-duty (4) SS Pin IIN(off) IEN/SS DMAX (4) (5) Minimum On-time tON(MIN) Thermal Shutdown Threshold TSD Temperature (4) Thermal Shutdown Restart TSD_hys Hysteresis of Temperature (4) High-side Switch ON RON(H) Resistance (4) (4) (5) Remarks Guaranteed by design, not tested. Input/ Output conditions are controlled by the minimum on time. NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 4 NR111D Efficiency, η (%) Typical Performance Characteristics Efficiency, η (%) 4. Output Current, IO (A) Efficiency (Vo = 3.3 V) Figure 4-2. Efficiency, η (%) 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 Output Current, IO (A) Figure 4-3. Efficiency (Vo = 5.0 V) NR114K UVLO Vo=3.3V L=47uH VO[V] VO (V) Output Voltage, Figure 4-1. Output Current, IO (A) Input Voltage, V (V) VIN[V]IN Efficiency (Vo = 12.0 V) Figure 4-4. Output Startup (Load = CR) ISET= GND Output Voltage, VO (V) Output Voltage, VO (V) 5.1 5.08 VIN = 8v 12v 24v 5.06 5.04 5.02 5 4.98 4.96 4.94 4.92 4.9 0 1 Output Current, IO (A) Figure 4-5. Overcurrent Protection 2 3 4 Output Current, IO (A) Figure 4-6. NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 Load Regulation 5 NR110K,111K,114K,115K,116K,117K IQ_off NR114K/115K,NR116K,NR117K IQ 5.0 0.40 4.5 0.35 Iin [mA] Input Current, IIN (mA) Iin [mA] IIN (mA) Input Current, NR111D 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.30 0.25 0.20 0.15 0.10 0.05 0.00 -0.05 0.5 -0.10 0.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 0.0 5.0 Input Voltage, VIN (V) VIN[V] Figure 4-7. 10.0 Input Figure 4-8. INNR110K Pin Sink focsCurrent at No Load 15.0 20.0 25.0 30.0 VIN[V] Voltage, VIN (V) Quiescent Current fosc [kHz] Frequency (kHz) Vo=3.3V L=10uH 500 480 460 440 420 400 380 360 340 320 300 280 260 240 220 200 0.0 1.0 2.0 3.0 4.0 5.0 Output Current, Io [A] IO (A) Figure 4-9. Operating Frequency NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 6 NR111D 5. Block Diagram IN 2 Σ OSC Pre Reg VREF ISET 6 Drive Reg 1 BS OCP REF 0.8 V EN 7 Current Sense Amp OCP ON/OFF M1 PWM Logic ISET OCP REF 3 SW Compensation Error amp. 0.8 V 5 FB SS TSD UVLO 4 GND 6. 8 SS Pin Configuration Definitions 1 BS SS 8 2 IN EN 7 3 SW 4 GND ISET 6 Pin Name 1 BS 2 IN FB 5 3 SW 4 GND 5 FB 6 ISET 7 EN 8 SS Descriptions High-side boost input pin. The power is supplied to the driver of highside Nch-MOSFET through the BS pin. A capacitor and a resistor are connected in series between the SW pin and the BS pin. This pin is input pin. The power is supplied to the IC through the IN pin. This pin is output pin. The power is output through the SW pin. Connect the LC filter for the output to the this pin. A capacitor is required to be connected between this pin and the BS pin to supply the power to the high-side MOSFET. Ground pin. To control constant voltage, the output voltage is input to the FB pin, and is compared with internal reference voltage. The feedback threshold voltage is 0.8 V. The output voltage is set by resistors connected to the FB pin. R5 and R6 are connected between the FB pin and output line. R4 is connected between the FB pin and the GND pin. OCP setting pin. This pin must be shorted to the ground. Enable signal input pin. When high signal is input to this pin, the internal regulator turns on. When low signal is input to this pin, the internal regulator turns off. Soft-start input. The soft-start period can be adjusted by the capacitor connected between the SS pin and the GND pin. The soft-start operation reduces the over-shoot of the output voltage and rush current. NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 7 NR111D 7. Typical Application R1 R3 NR111D 1 BS SS 8 2 IN EN 7 C10 3 SW 4 GND ISET 6 FB 5 L1 VIN VOUT R5 C1 C2 R4 C9 D1 GND Symbol C1 C2 C4 C5 C9 C10 C4 C5 R6 GND Ratings 10 μF / 35 V 10 μF / 35 V 22 μF / 16 V 22 μF / 16 V 0.1 μF 0.1 μF Symbol R1 R3 R4 R5 R6 L1 D1 NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 Ratings 510 kΩ 22 Ω 18 kΩ 2.7 kΩ (Vo = 5.0 V) 3.9 kΩ 10 μH 40 V, 5 A (Schottky diode) 8 NR111D 8. Physical Dimensions ● DIP8 NOTES: ● Dimensions in millimeters ● Not to scale ● Bare lead frame: Pb-free (RoHS compliant) NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 9 NR111D 9. Marking Diagram 8 NR111D Part Number SK 1 YM D Lot Number: Y is the last digit of the year of manufacture (0 to 9) M is the month of the year (1 to 9, O, N, or D) D is the period of days represented by: 1: the first 10 days of the month (1st to 10th) 2: the second 10 days of the month (11th to 20th) 3: the last – days of the month (21st to 31st) Control Number NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 10 NR111D The IC starts switching operation with minimum onduty or maximum on-duty. The high-side switching MOSFET, M1, is for supplying output power. At startup of IC, the SW pin becomes low status during short time to charge the boost capacitor, C10, for M1 driving. When M1 is on-status, the coil current is increased by applying the voltage the SW pin and the coil. In addition, the output of the current sense amplifier also increases. Signal A is sum of the current sense amplifier output and slope compensation signal. The comparator compares the signal A with the error amplifier output. When the signal A exceeds the output voltage of the error amplifier (Error Amp.), the current comparator output becomes “H” and the RS flip-flop circuit in PWM logic is reset. Then, M1 turns off, and the regenerative current flows through the Schottky diode, D1. The set signal is generated in each cycle, and set the RS flip-flop circuit. If the signal A does not exceed the output voltage of the error amplifier (Error Amp.), the signal of off duty circuit sets RS flip-flop circuit. 10. Operational Description 10.1. PWM Output Control The IC consists of total three blocks; two feedback loop systems (current control and voltage control) and one slope compensation. For the voltage control feedback, divided output voltage by resistor is input to the FB pin. The internal error amplifier compares the FB pin voltage with the reference voltage VREF = 0.8 V. For the current control feedback, the loop makes the coil current feedback to the PWM control. The coil current that is branched by using sense MOSFET is detected by the current sense amplifier. In addition, the slope compensation is made for current control slope in order to prevent subharmonic oscillations. The PWM control with current control method is achieved by calculating the voltage control feedback, the current control feedback and the slope compensation signals. (See Figure 10-1.) When UVLO is released or the EN pin or the SS pin voltage exceeds the threshold, the IC starts the switching operation. IN VIN 2 C1 Σ OSC Pre Reg VREF R1 0.8 V EN 7 Current Sense Amp OCP BS 1 Drive Reg R3 OCP REF M1 C10 A ON/OFF Comp. C2 SW 3 PWM Logic L1 Vo D1 R5 ISET 6 ISET OCP REF R4 Compensation Error amp. 0.8 V C4 C5 5 FB R6 SS TSD UVLO GND 4 SS 8 C9 Figure 10-1. Basic Structure of Chopper Type Regulator with PWM Control by Current Control NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 11 NR111D Figure 10-2 shows the SS pin internal circuit. When capacitor, CSS, is connected to the SS pin, the IC operates in soft start at startup. The output voltage, VO, increases depending on the charged voltage of CSS. Delay time, tDELAY is calculated by Equation (1). Soft start time, tSS is calculated by Equation (2). If the soft start function is unused, the SS pin is unconnected (open status). 0.9 (V) ISS t DLAY = CSS × (1) SS pin voltage at open is 3.0 V. Figure 10-4 shows the relationship between the CSS discharge time and CSS capacitance. CSS discharge time is require time that the SS pin voltage decreases to 0.9 V from 3.0 V CSS Discharge Time (ms) 10.2. Soft Start Function CSS discharge time CSS Capacitance (µF) t SS 1.79 (V) − 0.9 (V) = CSS × 0.9 × ISS (2) 5 IEN/SS = 10 μA SS 8 ×0.9 VREF = 0.8 V 0.9 V Error Amp. Figure 10-2. CSS Discharge Time vs. CSS Capacitance In case the CSS is short circuit status or the CSS value is set too small, the output capacitor is charged by the output current that is limited by overcurrent protection threshold current, Is. In the case, the time constant is calculated by Equation (3). This time constant is in no load status. When the circuit has some load, the load current is subtracted from Is. FB CSS Figure 10-4. SS Pin Internal Circuit t= COUT × VO IS (3) 10.3. External ON/OFF Function IN pin Voltge 4.1 V Time SS pin Voltage When the external signal is input to EN pin, the IC turns on/off the output. When the EN pin voltage is decreased to VEN = 1.4 V or less by open collector switch as shown in Figure 10-5, the switching operation stops. When the external on/off function is unused, pull up the EN pin to the IN pin by resister (510 kΩ) as shown in Figure 10-6. 1.79 V 0.9 V Time Output Voltage 510 kΩ NR111D Time tDELAY Figure 10-3. tSS Soft Start Operation Waveform Figure 10-5. NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 External ON/OFF Function 12 NR111D IO ≥ ∆IL 2 (5) 510 kΩ NR111D IO = IP − Figure 10-6. External ON/OFF Function Disabled 10.4. Overcurrent Protection The IC has an overcurrent protection (OCP) circuit. The OCP circuit detects the peak current of the switching transistor. When the peak current exceeds the setting current, the IC limits the current by forcibly shortening the on-time of transistor and decreasing the output voltage (see Figure 10-7). When the overcurrent state is released, the output voltage automatically returns. ∆IL 2 (6) In the discontinuous conduction mode (DCM), output current, IO, is calculated as follows: IO < ∆IL 2 IO = L × VIN × f ×I 2 2 × VO × (VIN − VO ) P (7) (8) 1 = × IP 2 2 × ∆IL Output Voltage 10.5. Thermal Shutdown Output Current Figure 10-7. Output Voltage Characteristics at Overcurrent The output current, IO, can be calculated using the OCP operation current, IP as shown in Equation (6) or Equation (8). When the on-duty is 50% or less, the inductance, L, is recommended to be the value that ΔIL is 0.3 A to 1.2 A. You must set the inductance that satisfies output current, IO, from the specifications (input voltage and output voltage) and IP. The thermal shutdown (TSD) circuit detects the junction temperature of the IC. When the junction temperature exceeds about 160 °C, TSD circuit is activated and stops the switching of the output transistor. Then, the output voltage decreases. When the junction temperature decreases about 20 °C from the TSD circuit activation temperature, the output voltage automatically returns. The TSD circuit protects from the heat generation for short time such as momentary short circuit. The operation and the reliabilities of the IC are not guaranteed under the continuous heat generation conditions such as short circuit for a long time. Output Voltage The ripple current of the choke coil, ΔIL, is calculated as follows: ∆IL = (VIN − VO ) × VO L × VIN × f TSD release temperature TSD activation temperature (4) where, VIN is input voltage, VO is output voltage, L is inductance the choke coil, and f is switching frequency. Junction Temperature Figure 10-8. Output Voltage Characteristics of Thermal Shutdown In the continuous conduction mode (CCM), output current, IO, is calculated as follows: NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 13 NR111D ΔIL is the ripple current of the choke coil. ILP is the peak current of the choke coil. ΔIL and ILP are calculated by following equations. 11. Design Notes 11.1. External Components Take care to use properly rated, including derating as necessary and proper type of components. R3 NR111D 1 BS R1 2 IN SS 8 4 GND VIN ISET 6 FB 5 L1 VOUT R5 C1 (VIN − VO ) × VO L × VIN × f ILP = ∆IL + IOUT 2 (9) (10) EN 7 C10 3 SW ∆IL = C2 C9 D1 C4 C5 R4 R6 GND As above equations, ΔIL and ILP increase according to decreasing the inductance, L. Thus, too small inductance setting may cause the unstable operation of the switching regulator because the coil current ripple becomes large. You must consider that the inductance of the choke coil decreases in the magnetic saturation condition such as overload and short circuit of load. GND Large inductance Figure 11-1. Small inductance The IC Peripheral Circuit 11.1.1. Choke Coil, L1 The choke coil, L1, is the most important component in chopper type switching regulators. In order to keep the stabilized regulator operation, the coil must be avoided the unsafe operation including the saturation condition or the over-heat excessively. If the winding resistance of the choke coil is too high, the efficiency decreases and may not be the setting value. The overcurrent protection threshold of NR111D is 5.5 A (Typ.). You must consider about the self-heating of the choke coil at the status including overload and the momentary short circuit. The selection points of the choke coil are as follows: ● Select choke coil for switching regulator. It is not recommended to use the coil for noise filter, since its power dissipation becomes high and causes high heat generation. ● Avoid a sub-harmonic oscillations. The current control that detects peak current may cause a sub-harmonic oscillation theoretically in the condition that the on-duty is over 50%. In the sub-harmonic oscillation, coil current is changed by the integer multiple of switching frequency. Thus, the IC compensates the coil current in internal to operate stably. Therefore, the inductance must be selected properly according to output voltage. Figure 11-2. Ripple Current of Choke Coil ● Fulfill the rated current. The rated current value of the choke coil must be set larger than the maximum load current, which is used. If the load current exceeds to the rated current value of the coil, the inductance of the coil decreaes rapidly and large current flows. ● Select the low noise type. The open magnetic circuit type core like a drum type may generate noise in peripheral circuit due to the magnetic flux passing outside of coil. It is recommended to use the Coils of closed magnetic circuit type core such as toroidal type, EI type and EE type. NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 14 NR111D 11.1.2. Input Capacitor, CIN The input capacitor, CIN, shows C1 and C2. CIN is the bypass capacitor of input circuit. It supplies the current of short pulses to the regulator during switching and compensates the input voltage drop. Thus, CIN should be placed as close the IC as possible. Even if the rectifying capacitor of an AC/DC convertor circuit is in input circuit, CIN is required when the rectifying capacitor is not placed near the IC. Since large ripple current flows through CIN, CIN must be used the capacitor for the switching regulator, which is for high frequency and has low impedance characteristics. The selection points of CIN are as follows: ● Fulfill the breakdown voltage rating. ● Fulfill sufficient allowable ripple current rating. IIN 2 VIN IN Ripple current CIN Figure 11-3. GND 4 Current Flow of Input Capacitor IIN 0 IV IP tON load current. The effective value of the ripple current, IINR(RMS), is calculated by Equation (11). IINR(RMS) ≈ 1.2 × VO × IO VIN (11) If VIN is 20 V, IO is 3 A, VO is 5 V, IINR(RMS) ≈ 1.2 × 5 (V) × 3 (A) = 0.9 (A) 20 (V) In the case, you must select the capacitor that the allowable ripple current is more than 0.9 A. 11.1.3. Output Capacitor, COUT The output capacitor, COUT, shows C4 and C5. In the current control method, the feedback loop which detects the inductor current is added to the voltage control method. The stable operation is achieved without considering the effect of the secondary delay factor of LC filter. Thus, the capacitance of the capacitor of the LC filter can be reduced. The IC can achieve the stable operation using the low ESR capacitor (ceramic capacitor). The COUT is the rectifying capacitor of switching output, and composes the LC low-pass filter with choke coil, L1. The current that is same of the ripple current of choke coil, ΔIL, flows through COUT. Therefore, you must consider derating for breakdown voltage and the allowable ripple current (See Section 11.1.2 Input Capacitor). Since large ripple current flows through COUT, COUT must be used the capacitor for the switching regulator, which is for high frequency and has low impedance characteristics. If the impedance of COUT is high, the IC may be occurred unstable switching operation in low temperature environment. T IL VO Figure 11-4. L1 Ripple current Current Waveform of Input Capacitor If the CIN voltage and ripple current is over the rating of the breakdown voltage and the allowable ripple current, or you does not consider derating for these rating, the following problem may be occurred. Thus, you must consider derating for breakdown voltage and the allowable ripple current. ● The capacitor life time short (burst, capacitance decreasing, equivalent impedance increasing, etc.) ● The unstable switching operation of the IC. ESR Io RL COUT Figure 11-5. Current Flow of Output Capacitor The ripple current of CIN increases depending on the NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 15 NR111D 11.1.4. Freewheel Diode, D1 IO ∆IL 0 Figure 11-6. Current Waveform of Output Capacitor The ripple current of COUT is same with the ripple current of the choke coil, and does not depend on the load current. Thus, the effective value of the ripple current, IOR(RMS), is calculated by Equation (12). IOR(RMS) = ∆IL Flywheel diode, D1, is for discharging energy that is charged choke coil in off-status. External flywheel diode, D1, improves efficiency, and must be used a Schottky-barrier diode. If the fast recovery diode is used, the IC may be damaged by the reverse voltage that is caused by the surge at turn-on or the forward voltage in on-status. Since the output voltage of the SW pin (3 pin) is nearly same with input voltage, the reverse breakdown voltage of D1 is required more than the input voltage. You must not use ferrite beads for the flywheel diode. (12) 2√3 If ΔIL is 0.5 A, IOR(RMS) = 0.5 (A) 2√3 ≈ 0.14 (A) In the case, you must select the capacitor that the allowable ripple current is more than 0.14 A. The output ripple voltage of the IC, VRIP, is calculated by Equation (13). VRIP = ∆IL × COUT ESR (13) Where, ΔIL is the ripple current of the choke coil (same of the ripple current of COUT), and COUTESR is the equivalent series resistance (ESR) of COUT. From Equation (13), you should set the low ESR capacitor in order to reduce the output ripple voltage. In same family of the electrolytic capacitor, the larger capacitance in same the rating voltage, or the higher rating voltage (the larger package size) in same capacitance is, the lower the ESR generally becomes. If ΔIL is 0.5 A, VRIP is 40 mV, COUT ESR = VRIP 40(mV) = = 80 (mΩ) ∆IL 0.5 (A) (14) In the case, you must select the capacitor that the ESR is less than 80 mΩ In addition, the ESR depends on temperature, and generally increases in low temperature. Thus, you should check the ESR at the actual used temperature. The ESR characteristic is shown in each capacitor maker. NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 16 11.1.5. Output Voltage, VO, and Output Capacitor The output capacitor determines according to the output voltage VO. In each voltage, Table 11-1 shows the capacitance that the IC can operate stable. The values are reference. The ESR of the electrolytic capacitor is about 100 mΩ. See Section 11.1.1 about the inductance, L, setting. Table 11-1. Output Voltage, VO, vs. Output Capacitor (NR111D: 350 kHz) VO (V) 1.2 1.8 3.3 5 9 12 14 Output Capacitor (µF) Electrolytic Capacitor Ceramic Capacitor (ESR ≈ 100 mΩ) 33 to 100 47 to 330 22 to 100 47 to 470 10 to 68 20 to 180 4.7 to 47 4.7 to 100 3.3 to 22 2.2 to 47 3.3 to 22 2.2 to 33 2.2 to 22 2.2 to 33 11.2. Allowable power dissipation The power dissipation of the IC must be within the allowable power dissipation shown in Figure 11-7, and is calculated by Equation Figure 11-7. P = VO × IO × ( 100 VO − 1) −VF × IO × (1 − ) ηx VIN (15) where, VO is output voltage, VIN is Input voltage, IO is output curent, VF is diode forward voltage, and ηx is efficiency (%). Since the efficiency determines from the input voltage and output current, it shall be obtained from the efficiency curve and substituted in percent. The heat release setting of the freewheel diode is required separately. Allowable Power Dissipation, PD (W) NR111D Ambient Temperature, TA (°C) NOTES ● Glass-epoxy board, 70 mm × 60 mm ● Copper area, 1310 mm2 ● The power dissipation is calculated at the junction temperature 125 °C. Figure 11-7. Allowable Power Dissipation Curve 11.2.1. Power Supply Stability The phase characteristics of a chopper type regulator are the synthesis of follows. The internal phase characteristics of a regulator IC, the output capacitor, and the load resistance. Internal phase characteristics of a regulator IC are generally determined by the delay time of control block and the phase characteristics of the output error amplifier. Therefore, the phase delay due to the delay time of the control block rarely causes problems in actual use. The IC has phase compensation for output error amplifier. See Section 11.1.5 about the output voltage setting and the output current setting for stable operation. 11.2.2. Spike Noise Reduction This section shows how to reduce spike noises. Extra attentions should be paid when you measure spike noises using an oscilloscope. The ground lead of a probe should be as short as possible, and should be connected to root of output capacitor. When the ground lead is long, the noises may be measured larger than actual noises because the ground lead becomes an antenna. ● Add a resistance to the BS pin in series. When the resister, R3, is added between the BS pin and SW pin as shown in Figure 11-8, the turn-on switching speed of the internal power MOSFET becomes slow. The spike noises is reduced according to decreasing switching speed. The maximum value of R3 is 22 Ω. If R3 is set too large, the following event may be NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 17 NR111D occured. Start-up failure. The IC is damaged by self-heating due to decreasing the gate voltage of internal power MOSFET. In the area, bead cores must not be used. NR111D VIN IN 1 BS Vo 2 3 SW 7 Control Circuit EN 8 SS GND 6 FB ISET GND NR111D GND Figure 11-10. Figure 11-8. 4 5 BS pin peripheral circuit ● Add a snubber circuit. When an RC snubber (a resistor and a capacitor) is added to the SW pin as shown in Figure 11-9, the spike noises are reduced because the slopes of output waveform and the recovery current waveform of the diode become shallow. Note that the efficiency is decreased as the swiching loss of the internal power MOSFET increases. Note when you add bead cores 11.2.3. Reverse Bias Condition When the IN pin voltage becomes higher than the SW pin voltage (battery charger application, etc.), the diode for reverse bias protection must be connected between the IN pin and SW pin as shown in Figure 11-11. NR111D NR111D About 10 Ω About 1000 pF Figure 11-9. Figure 11-11. When the IN pin voltage becomes higher than the SW pin voltage SW pin peripheral circuit ● Note when you add bead cores Bead cores incruding ferrite beads must not be used in the broken line in Figure 11-10. When you layouts the PCB trace of the switching regurator, the parasitic inductance of PCB trace should be as small as possible. If bead cores are added, the the inductance of the bead cores is added to the parasitic inductance of PCB trace. It may causes the malfunction or break of the IC by the unstable status including negative potential grounding due to surge voltage. The noise reduction method should be chosen from above method (add the BS pin resistor or the snubber ciecuit). NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 18 NR111D 11.3. Pattern Layout 11.3.1. Large Current Trace Since large current flows through the bold line in Figure 11-12, these PCB traces must be as wide and small loop as possible. The output voltage is set by the resisters connected to the FB pin (R4, R5 and R6). The minimum current flowing through the FB pin, IFB, should be set about 0.2 mA. The maximum value of IFB should be set considering about the efficiency. The output voltage, VO, and the value of R4, R5 and R6 are calculated by the following equations. IFB = R1 VFB R6 (16) NR111D R3 1 BS SS 8 2 IN EN 7 where, VFB is 0.8 V ± 2%. C10 3 SW ISET 6 4 GND R4 + R5 = FB 5 L1 VIN VOUT VO − VFB VO − 0.8 = (Ω) IFB 0.2 × 10−3 (17) R5 C1 C2 R4 C9 D1 C4 C5 VFB 0.8 = ≈ 3.9 (kΩ) IFB 0.2 × 10−3 GND VO = (R4 + R5) × Input capacitors (C1 and C2) and output capacitors (C4 and C5) are placed as close the IC as possible. Even if the rectifying capacitor of an AC/DC convertor circuit is in input circuit, input capacitors are required when the rectifying capacitor is not placed near the IC. The traces of these capacitors are drawn wide (see Figure 11-13-(a), Proper Trace) (19) If the output voltage is set to 0.8 V that is same voltage with VFB, R6 should be connected to operate stable. The relationship between input voltage and output voltage is determined by the on-time of the SW pin. The on-time is recommended to set to more than 200 ns. The traces connected to the FB pin and the R4, R5, R6 must not be placed in parallel with the trace connected to the freewheel diode, because switching noise affects to the feedback detection voltage, and may occur unstable operations. Especially, the trace between FB pin and R6 must be as short as possible. SW Figure 11-13. VFB + VFB R6 Large Current Line 11.3.2. Input and Output Capacitor (a) Proper Trace (18) R6 GND Figure 11-12. R6 = R5 (b) Improper Trace Trace Example of Capacitors 11.3.3. FB Pin Setting (Output Voltage Setting) The FB pin detects the feedback signal to control the output voltage, and should be placed as close the output capacitor as possible. If the FB pin is far from the output capacitor, the unstable operation may be occurred by the regulation decreasing and the switching ripple increasing. Vo 3 FB 5 GND 4 R4 IFB R6 GND Figure 11-14. NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 FB pin peripheral circuit 19 NR111D 12. Pattern Layout Example Ground trace must be connected as short as possible to the GND pin at single point grounding. (a) Front Side (Components is mounted) Figure 12-1. (b) Back Side (Ground pattern) Pattern Layout Example (PCB size: 40 mm × 40 mm) NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 20 NR111D R7 Z1 D2 R3 1 BS SS 8 2 IN EN 7 3 SW ISET 6 4 GND Vin R1 FB 5 C10 L1 Vo R8 R5 VoS VinS C11 R4 C1 C2 C6 C9 C4 C5 R2 D1 R10 R6 C12 GND GND Figure 12-2. Pattern Layout Example Circuit Table 12-1. Bill of Materials Symbol C1 C2 C4 C5 C6* C9 C10 C11* C12* Ratings Ceramic, 10 μF / 35 V Ceramic, 10 μF / 35 V Ceramic, 22 μF / 16 V Ceramic, 22 μF / 16 V Option Ceramic, 0.1 μF Ceramic, 0.1 μF Option Option Symbol D1 D2* L1 R1 R2* R3 R4 R5 R6 Ratings Schottky 40 V, 5.0 A Option 10 μH 510 kΩ Option 22 Ω 18 kΩ 2.7 kΩ (Vo = 5.0 V) 3.9 kΩ Symbol R7 R8* R10* Z1 Ratings Open Option Option Buck converter, NR111D * It is necessary to be adjusted based on actual operation in the application. NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 21 NR111D Important Notes ● All data, illustrations, graphs, tables and any other information included in this document (the “Information”) as to Sanken’s products listed herein (the “Sanken Products”) are current as of the date this document is issued. The Information is subject to any change without notice due to improvement of the Sanken Products, etc. Please make sure to confirm with a Sanken sales representative that the contents set forth in this document reflect the latest revisions before use. ● The Sanken Products are intended for use as components of general purpose electronic equipment or apparatus (such as home appliances, office equipment, telecommunication equipment, measuring equipment, etc.). Prior to use of the Sanken Products, please put your signature, or affix your name and seal, on the specification documents of the Sanken Products and return them to Sanken. When considering use of the Sanken Products for any applications that require higher reliability (such as transportation equipment and its control systems, traffic signal control systems or equipment, disaster/crime alarm systems, various safety devices, etc.), you must contact a Sanken sales representative to discuss the suitability of such use and put your signature, or affix your name and seal, on the specification documents of the Sanken Products and return them to Sanken, prior to the use of the Sanken Products. The Sanken Products are not intended for use in any applications that require extremely high reliability such as: aerospace equipment; nuclear power control systems; and medical equipment or systems, whose failure or malfunction may result in death or serious injury to people, i.e., medical devices in Class III or a higher class as defined by relevant laws of Japan (collectively, the “Specific Applications”). Sanken assumes no liability or responsibility whatsoever for any and all damages and losses that may be suffered by you, users or any third party, resulting from the use of the Sanken Products in the Specific Applications or in manner not in compliance with the instructions set forth herein. ● In the event of using the Sanken Products by either (i) combining other products or materials or both therewith or (ii) physically, chemically or otherwise processing or treating or both the same, you must duly consider all possible risks that may result from all such uses in advance and proceed therewith at your own responsibility. ● Although Sanken is making efforts to enhance the quality and reliability of its products, it is impossible to completely avoid the occurrence of any failure or defect or both in semiconductor products at a certain rate. You must take, at your own responsibility, preventative measures including using a sufficient safety design and confirming safety of any equipment or systems in/for which the Sanken Products are used, upon due consideration of a failure occurrence rate and derating, etc., in order not to cause any human injury or death, fire accident or social harm which may result from any failure or malfunction of the Sanken Products. Please refer to the relevant specification documents and Sanken’s official website in relation to derating. ● No anti-radioactive ray design has been adopted for the Sanken Products. ● The circuit constant, operation examples, circuit examples, pattern layout examples, design examples, recommended examples, all information and evaluation results based thereon, etc., described in this document are presented for the sole purpose of reference of use of the Sanken Products. ● Sanken assumes no responsibility whatsoever for any and all damages and losses that may be suffered by you, users or any third party, or any possible infringement of any and all property rights including intellectual property rights and any other rights of you, users or any third party, resulting from the Information. ● No information in this document can be transcribed or copied or both without Sanken’s prior written consent. ● Regarding the Information, no license, express, implied or otherwise, is granted hereby under any intellectual property rights and any other rights of Sanken. ● Unless otherwise agreed in writing between Sanken and you, Sanken makes no warranty of any kind, whether express or implied, including, without limitation, any warranty (i) as to the quality or performance of the Sanken Products (such as implied warranty of merchantability, and implied warranty of fitness for a particular purpose or special environment), (ii) that any Sanken Product is delivered free of claims of third parties by way of infringement or the like, (iii) that may arise from course of performance, course of dealing or usage of trade, and (iv) as to the Information (including its accuracy, usefulness, and reliability). ● In the event of using the Sanken Products, you must use the same after carefully examining all applicable environmental laws and regulations that regulate the inclusion or use or both of any particular controlled substances, including, but not limited to, the EU RoHS Directive, so as to be in strict compliance with such applicable laws and regulations. ● You must not use the Sanken Products or the Information for the purpose of any military applications or use, including but not limited to the development of weapons of mass destruction. In the event of exporting the Sanken Products or the Information, or providing them for non-residents, you must comply with all applicable export control laws and regulations in each country including the U.S. Export Administration Regulations (EAR) and the Foreign Exchange and Foreign Trade Act of Japan, and follow the procedures required by such applicable laws and regulations. ● Sanken assumes no responsibility for any troubles, which may occur during the transportation of the Sanken Products including the falling thereof, out of Sanken’s distribution network. ● Although Sanken has prepared this document with its due care to pursue the accuracy thereof, Sanken does not warrant that it is error free and Sanken assumes no liability whatsoever for any and all damages and losses which may be suffered by you resulting from any possible errors or omissions in connection with the Information. ● Please refer to our official website in relation to general instructions and directions for using the Sanken Products, and refer to the relevant specification documents in relation to particular precautions when using the Sanken Products. ● All rights and title in and to any specific trademark or tradename belong to Sanken and such original right holder(s). DSGN-CEZ-16003 NR111D-DSE Rev.1.7 SANKEN ELCTRIC CO., LTD. Dec. 07, 2022 https://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO., LTD. 2012 22