NJW4170 Current Mode Control High Speed Frequency Internal 1A MOSFET Switching Regulator IC for Buck Converter GENERAL DESCRIPTION ■ PACKAGE OUTLINE The NJW4170 is a high speed oscillating frequency buck converter with 40V/1A MOSFET. Current mode control and built-in phase compensation circuit minimize external parts and contribute to using a Low ESR Output Capacitor(MLCC) within wide input range from 4.5V to 40V. Therefore, the NJW4170 can realize downsizing of applications. Also, it has a soft start function, an external clock synchronization function, an over current protection and a thermal shutdown circuit. Over 2MHz of Switching frequency can avoid interference with the AM radio frequency. It is suitable for supplying power to a Car Accessory, Audio Automation Equipment, Industrial Instrument and so on. FEATURES Oscillating Frequency NJW4170U2 NJW4170KV1 2.4MHz typ. (A ver.) 2.1MHz typ. (B ver.) 80ns typ.(A ver.) 85ns typ.(B ver.) Minimum ON time Current mode Control External Clock Synchronization Wide Operating Voltage Range 4.5V to 40V Switching Current 1.4A min. PWM Control Built-in Compensation Circuit Correspond to Ceramic Capacitor (MLCC) Soft Start Function 4ms typ. UVLO (Under Voltage Lockout) Over Current Protection (Hiccup type) Thermal Shutdown Protection Standby Function Package Outline NJW4170U2 : SOT-89-5 NJW4170KV1 : DFN8-V1(ESON8-V1) PRODUCT CLASSIFICATION Version Oscillating Frequency Package NJW4170U2-A A 2.4MHz typ. SOT-89-5 NJW4170KV1-A A 2.4MHz typ. DFN8-V1 (ESON8-V1) NJW4170U2-B B 2.1MHz typ. SOT-89-5 Part Number Ver.2016-01-25 Operating Temperature Range General Spec. -40 C to +125 C General Spec. -40 C to +125 C General Spec. -40 C to +125 C -1- NJW4170 PIN CONFIGURATION 5 V+ EN/SYNC 1 GND 2 (2) GND IN- 3 SW N.C. V+ N.C. 1 2 3 4 8 7 6 5 INN.C. GND EN/SYNC 4 SW 8 7 6 5 1 2 3 4 Exposed PAD on backside connect to GND. (Top View) (Bottom View) NJW4170KV1 NJW4170U2 PIN DESCRIPTIONS PIN NAME PIN NUMBER DFN8-V1 SOT-89-5 (ESON8) EN/SYNC 1 5 GND 2 6 IN- 3 8 SW V+ N.C. Exposed PAD 4 5 – 1 3 2, 4, 7 – – -2- FUNCTION Standby Control pin The EN/SYNC pin internally pulls down with 100k . Normal Operation at the time of High Level. Standby Mode at the time of Low Level or OPEN. Moreover, it operates by inputting clock signal at the oscillatory frequency that synchronized with the input signal. GND pin Output Voltage Detecting pin Connects output voltage through the resistor divider tap to this pin in order to voltage of the IN- pin become 0.8V. Switch Output pin of Power MOSFET Power Supply pin for Power Line Non connection Connect to GND (Only DFN8-V1 PKG) Ver.2016-01-25 NJW4170 BLOCK DIAGRAM V+ SLOPE COMP. CURRENT SENSE UVLO OCP EN/SYNC High: ON Low : OFF(Standby) Enable (Standby) 100k SYNC S Q OSC Buffer R SW TSD PWM INER AMP Soft Start Vref 0.8V GND Ver.2016-01-25 -3- NJW4170 ABSOLUTE MAXIMUM RATINGS PARAMETER SYMBOL Supply Voltage V+ + V - SW pin Voltage VV-SW EN/SYNC pin Voltage VEN/SYNC IN- pin Voltage VINPower Dissipation Junction Temperature Range Operating Temperature Range Storage Temperature Range PD MAXIMUM RATINGS -0.3 to +45 +45 -0.3 to +45 -0.3 to +6 625 (*1) SOT-89-5 2,400 (*2) mW DFN8-V1 (ESON8-V1) Tj Topr Tstg (Ta=25°C) UNIT V V V V 600 (*3) 1,800 (*4) -40 to +150 -40 to +125 -50 to +150 C C C 2 (*1): Mounted on glass epoxy board. (76.2×114.3×1.6mm:based on EIA/JDEC standard size, 2Layers, Cu area 100mm ) (*2): Mounted on glass epoxy board. (76.2×114.3×1.6mm:based on EIA/JDEC standard, 4Layers) (For 4Layers: Applying 74.2×74.2mm inner Cu area and a thermal via hall to a board based on JEDEC standard JESD51-5) (*3): Mounted on glass epoxy board. (101.5 114.5 1.6mm: based on EIA/JEDEC standard, 2Layers FR-4, with Exposed Pad) (*4): Mounted on glass epoxy board. (101.5 114.5 1.6mm: based on EIA/JEDEC standard, 4Layers FR-4, with Exposed Pad) (For 4Layers: Applying 99.5 99.5mm inner Cu area and a thermal via hole to a board based on JEDEC standard JESD51-5) RECOMMENDED OPERATING CONDITIONS PARAMETER SYMBOL Supply Voltage V+ External Clock Input Range A version fSYNC B version -4- MIN. 4.5 TYP. – MAX. 40 UNIT V 2.3 2.0 – – 2.8 2.5 MHz Ver.2016-01-25 NJW4170 (Unless otherwise noted, V+=VEN/SYNC=12V, Ta=25 C) ELECTRICAL CHARACTERISTICS PARAMETER SYMBOL Under Voltage Lockout Block ON Threshold Voltage OFF Threshold Voltage Hysteresis Voltage VT_ON VT_OFF VHYS tSS Soft Start Block Soft Start Time TEST CONDITION MIN. TYP. MAX. UNIT V+= L → H V+= H → L 4.2 4.11 70 4.35 4.26 90 4.5 4.41 – V V mV VB=0.75V 2.5 4 8 ms A version, VIN-=0.7V B version, VIN-=0.7V A version, VIN-=0.2V B version, VIN-=0.2V 2.2 1.9 – – 2.4 2.1 340 290 2.6 2.3 – – MHz MHz kHz kHz Oscillator Block Oscillating Frequency Oscillating Frequency (Low Frequency Control) Oscillating Frequency deviation (Supply voltage) Oscillating Frequency deviation (Temperature) Error Amplifier Block Reference Voltage Input Bias Current PWM Comparate Block Maximum Duty Cycle Minimum ON Time1 (Use Built-in Oscillator) Minimum ON Time2 (Use Ext CLK) Ver.2016-01-25 fOSC fOSC_LOW fDV V+=4.5 to 40V – 1 – % fDT Ta= -40 C to +85 C – 5 – % -1.0% -0.1 0.8 – +1.0% +0.1 V A 77.5 – – – – 82 80 85 80 85 – 115 120 115 120 % ns ns ns ns VB IB MAXDUTY tON-min1 tON-min2 A, B version, VIN-=0.7V A version B version A version, fSYNC =2.6kHz B version, fSYNC =2.3kHz -5- NJW4170 (Unless otherwise noted, V+=VEN/SYNC=12V, Ta=25 C) ELECTRICAL CHARACTERISTICS PARAMETER SYMBOL Over Current Protection Block Cool Down Time tCOOL Output Block Output ON Resistance Switching Current Limit SW Leak Current RON ILIM ILEAK Standby Control / Sync Block EN/SYNC pin High Threshold Voltage EN/SYNC pin Low Threshold Voltage Input Bias Current (EN/SYNC pin) MIN. TYP. MAX. UNIT – 75 – ms VEN/SYNC=0V, V+=40V, VSW=0V – 1.4 – 0.4 1.9 – 0.65 2.4 1 A A VTHH_EN/SYNC VEN/SYNC= L → H 1.6 – V+ V VTHL_EN/SYNC VEN/SYNC= H → L 0 – 0.5 V VEN/SYNC=12V – 270 390 A – 2.0 2.4 mA – – 1 A IEN TEST CONDITION ISW=1A General Characteristics Quiescent Current Standby Current -6- IDD IDD_STB A, B version, RL=no load, VIN-=0.9V VEN/SYNC=0V Ver.2016-01-25 NJW4170 POWER DISSIPATION vs. AMBIENT TEMPERATURE NJW4170KV1 (DFN8-V1 Package) Power Dissipation vs. Ambient Temperature (Tj=~150°C) NJW4170U2 (SOT89-5 Package) Power Dissipation vs. Ambient Temperature (Tj=~150°C) 3000 At on 4 layer PC Board (*6) At on 2 layer PC Board (*5) 2500 Power Dissipation PD (mW) Power Dissipation PD (mW) 3000 2000 1500 1000 500 At on 4 layer PC Board (*8) At on 2 layer PC Board (*7) 2500 2000 1500 1000 500 0 0 -50 -25 0 25 50 75 100 125 -50 150 -25 0 25 50 75 100 125 150 Ambient Temperature Ta (°C) Ambient Temperature Ta (°C) 2 (*5): Mounted on glass epoxy board. (76.2×114.3×1.6mm:based on EIA/JDEC standard size, 2Layers, Cu area 100mm ) (*6): Mounted on glass epoxy board. (76.2×114.3×1.6mm:based on EIA/JDEC standard, 4Layers) (For 4Layers: Applying 74.2×74.2mm inner Cu area and a thermal via hall to a board based on JEDEC standard JESD51-5) (*7): Mounted on glass epoxy board. (101.5 114.5 1.6mm: based on EIA/JEDEC standard, 2Layers FR-4, with Exposed Pad) (*8): Mounted on glass epoxy board. (101.5 114.5 1.6mm: based on EIA/JEDEC standard, 4Layers FR-4, with Exposed Pad) (For 4Layers: Applying 99.5 99.5mm inner Cu area and a thermal via hole to a board based on JEDEC standard JESD51-5) TYPICAL APPLICATIONS L VIN VOUT CIN V+ CFB SW R2 NJW4170 EN/ SYNC GND IN- SBD COUT R1 EN/SYNC High: ON Low: OFF (Standby) Ver.2016-01-25 -7- NJW4170 TYPICAL CHARACTERISTICS (A, B version) Reference Voltage vs. Supply Voltage (Ta=25ºC) Reference Voltage :VB (V) 0.81 0.805 0.8 0.795 0.79 Switching Current Limit :ILIM (A) 10 20 30 Supply Voltage :V+ (V) 0.795 40 -50 Switching Current Limit vs. Temperature 2.4 2.2 2 V+=12V V+=40V 1.8 1.6 V+=5V 1.4 1.2 -25 0 25 50 75 100 125 150 Temperature : (ºC) Output ON Resistance vs. Temperature (ISW=1A) 0.8 0.7 0.6 0.5 0.4 V+=5V V+=40V V+=12V 0.3 0.2 0.1 0 -50 -25 0 25 50 75 100 125 150 Temperature : (ºC) -50 -25 0 25 50 75 100 125 150 Temperature : (ºC) Maximum Duty Cycle vs. Temperature (V+=12V, VIN-=0.7V) 90 Maximum Duty Cycle :MAXDUTY (%) 0.8 0.79 0 2.6 0.805 Output ON Resistance :RON (Ω) Reference Voltage :VB (V) 0.81 Reference Voltage vs. Temperature (V+=12V) 88 86 84 82 80 78 76 -50 -8- -25 0 25 50 75 100 125 150 Temperature : (ºC) Ver.2016-01-25 NJW4170 TYPICAL CHARACTERISTICS (A, B version) Under Voltage Lockout Voltage vs. Temperature 4.5 8 Soft Start Time :tSS (ms) Threshold Voltage : (V) 4.45 4.4 4.35 VT_ON 4.3 4.25 4.2 VT_OFF 4.1 6 5 4 2 -50 -25 0 25 50 75 100 125 150 Temperature : (ºC) -50 Switching Leak Current vs. Temperature (V+=40V, VEN/SYNC=0V, VSW=0V) 1.5 1 0.5 0 -25 0 25 50 75 100 125 150 Temperature : (ºC) Standby Current vs. Temperature (VEN/SYNC=0V) 1 Standby Current :IDD_STB (μA) 2 Switching Leak Current :ILEAK (μA) 7 3 4.15 0.8 0.6 0.4 V+=40V V+=12V V+=4.5V 0.2 0 -50 -25 0 25 50 75 100 125 150 Temperature : (ºC) -50 Quiescent Current vs. Supply Voltage (RL=no Load, VIN-=0.9V, Ta=25ºC) 3 2.5 2 1.5 1 0.5 0 -25 0 25 50 75 100 125 150 Temperature : (ºC) Quiescent Current vs. Temperature (RL=no Load, VIN-=0.9V) 3 Quiescent Current :IDD (mA) Quiescent Current :IDD (mA) Soft Start Time vs. Temperature (V+=12V, VB=0.75V) 2.5 2 V+=4.5V, 12V, 40V 1.5 1 0.5 0 0 Ver.2016-01-25 10 20 30 Supply Voltage :V+ (V) 40 -50 -25 0 25 50 75 100 125 150 Temperature : (ºC) -9- NJW4170 TYPICAL CHARACTERISTICS (A version) Oscillating Frequency vs. Supply Voltage (A ver., VIN-=0.7V, Ta=25ºC) 2.8 Oscillating Frequency :fOSC (MHz) Oscillating Frequency :fOSC (MHz) 2.8 2.7 2.6 2.5 2.4 2.3 2.2 2.1 2 2.7 2.6 2.5 2.4 2.3 2.2 2.1 2 0 10 20 30 Supply Voltage : V+ (V) 40 -50 -25 0 25 50 75 100 125 150 Temperature : (ºC) Minimum ON Time1 vs. Temperature (A ver., V+=12V) 120 Minimum ON Time1 :tON-min1 (ns) Oscillating Frequency vs Temperature (A ver., V+=12V, VIN-=0.7V) 110 100 90 80 70 60 50 40 -50 - 10 - -25 0 25 50 75 100 125 150 Temperature : (ºC) Ver.2016-01-25 NJW4170 TYPICAL CHARACTERISTICS (B version) Oscillating Frequency vs. Supply Voltage (B ver., VIN-=0.7V, Ta=25ºC) 2.4 Oscillating Frequency :fOSC (MHz) Oscillating Frequency :fOSC (MHz) 2.4 2.3 2.2 2.1 2 1.9 1.8 2.3 2.2 2.1 2 1.9 1.8 0 10 20 30 Supply Voltage :V+ (V) 40 -50 -25 0 25 50 75 100 125 150 Temperature : (ºC) Minimum ON Time1 vs. Temperature (B ver., V+=12V) 120 Minimum ON Time1 :tON-min1 (ns) Oscillating Frequency vs Temperature (B ver., V+=12V, VIN-=0.7V) 110 100 90 80 70 60 50 40 -50 Ver.2016-01-25 -25 0 25 50 75 100 125 150 Temperature : (ºC) - 11 - NJW4170 NJW4170Application Manual Technical Information Description of Block Features 1. Basic Functions / Features Error Amplifier Section (ER AMP) 0.8V±1% precise reference voltage is connected to the non-inverted input of this section. To set the output voltage, connects converter's output to inverted input of this section (IN- pin). If requires output voltage over 0.8V, inserts resistor divider. Because the optimized compensation circuit is built-in, the application circuit can be composed of minimum external parts. PWM Comparator Section (PWM), Oscillating Circuit Section (OSC) The NJW4170 uses a constant frequency, current mode step down architecture. The oscillating frequency are 2.4MHz (typ.) at A version and 2.1MHz (typ.) at B version. The PWM signal is output by feedback of output voltage and slope compensation switching current at the PWM comparator block. The maximum duty ratio is 82% (typ.). The minimum ON time are limited to 80ns (typ.) at A version and 85ns (typ.) at B version. The buck converter of ON time is decided the following formula. ton VOUT s VIN fOSC VIN shows input voltage and VOUT shows output voltage. When the ON time becomes below in tON-min, in order to maintain output voltage at a stable state, change of duty or pulse skip operation may be performed. Power MOSFET (SW Output Section) The power is stored in the inductor by the switch operation of built-in power MOSFET. The output current is limited to 1.4A(min.) the overcurrent protection function. In case of step-down converter, the forward direction bias voltage is generated with inductance current that flows into the external regenerative diode when MOSFET is turned off. The SW pin allows voltage between the V+ pin and the SW pin up to +45V. However, you should use an Schottky diode that has low saturation voltage. Power Supply, GND pin (V+ and GND) In line with switching element drive, current flows into the IC according to frequency. If the power supply impedance provided to the power supply circuit is high, it will not be possible to take advantage of IC performance due to input voltage fluctuation. Therefore insert a bypass capacitor close to the V+ pin – the GND pin connection in order to lower high frequency impedance. - 12 - Ver.2016-01-25 NJW4170 Application Manual NJW4170 Technical Information Description of Block Features (Continued) 2. Additional and Protection Functions / Features Under Voltage Lockout (UVLO) The UVLO circuit operating is released above V+=4.35V(typ.) and IC operation starts. When power supply voltage is low, IC does not operate because the UVLO circuit operates. There is 90mV(typ.) width hysteresis voltage at rise and decay of power supply voltage. Hysteresis prevents the malfunction at the time of UVLO operating and releasing. Soft Start Function (Soft Start) The output voltage of the converter gradually rises to a set value by the soft start function. The soft start time is 4ms (typ.). It is defined with the time of the error amplifier reference voltage becoming from 0V to 0.75V. The soft start circuit operates after the release UVLO and/or recovery from thermal shutdown. The operating frequency is controlled with a low frequency 340kHz (typ.) at A version and 290kHz (typ.) at B version, until voltage or the IN- pin becomes approximately 0.4V. 0.8V Vref, IN- pin Voltage OSC Waveform ON SW pin OFF UVLO(4.35V typ.) Release, Standby, Recover from Thermal Shutdown Low Frequency Control VIN-=approx 0.4V Soft Start time: Tss=4ms(typ.) to VB=0.75V Steady Operaton Soft Start effective period to VB=0.8V Fig. 1. Startup Timing Chart Ver.2016-01-25 - 13 - NJW4170 NJW4170Application Manual Technical Information Description of Block Features (Continued) Over Current Protection Circuit (OCP) NJW4170 contains overcurrent protection circuit of hiccup architecture. The overcurrent protection circuit of hiccup architecture is able to decrease heat generation at the overload. The NJW4170 output returns automatically along with release from the over current condition. At when the switching current becomes ILIM or more, the overcurrent protection circuit is stopped the MOSFET output. The switching output holds low level down to next pulse output at OCP operating. When IN- pin voltage becomes 0.3V or less, it operates with 340kHz (typ.) at A version and 290kHz (typ.) at B version. At the same time starts pulse counting, and stops the switching operation when the overcurrent detection continues 128 pulses. After NJW4170 switching operation was stopped, it restarts by soft start function after the cool down time of approx 75ms (typ.). IN- pin Voltage 0.8V 0.3V 0V Oscillating Frequency A ver.=2.4MHz typ. B ver.=2.1MHz typ. OCP Operates Oscillating Frequency A ver.=340kHz typ. B ver.=290kHz typ. ON SW pin OFF Switching Current ILIM 0 Pulse by Pulse Static Status Pulse Count :128 pulse Cool Down time :75ms typ. Detect Overcurrent Soft Start Fig. 2. Timing Chart at Over Current Detection Thermal Shutdown Function (TSD) When Junction temperature of the NJW4170 exceeds the 165°C*, internal thermal shutdown circuit function stops SW function. When junction temperature decreases to 150°C* or less, SW operation returns with soft start operation. The purpose of this function is to prevent malfunctioning of IC at the high junction temperature. Therefore it is not something that urges positive use. You should make sure to operate within the junction temperature range rated (150 C). (* Design value) Standby Function The NJW4170 stops the operating and becomes standby status when the EN/SYNC pin becomes less than 0.5V. The EN/SYNC pin internally pulls down with 100k , therefore the NJW4170 becomes standby mode when the EN/SYNC pin is OPEN. You should connect this pin to V+ when you do not use standby function. - 14 - Ver.2016-01-25 NJW4170 Application Manual NJW4170 Technical Information Description of Block Features (Continued) External Clock Synchronization By inputting a square wave to EN/SYNC pin, can be synchronized to an external frequency. You should fulfill the following specification about a square wave. (Table 1.) Table 1. The input square wave to an EN/SYNC pin. A version B version (fOSC =2.4MHz) (fOSC =2.1MHz) Input Frequency 2.3MHz to 2.8MHz 2.0MHz to 2.5MHz Duty Cycle 40% to 60% Voltage 1.6V or more at High level magnitude 0.5V or less at Low level The trigger of the switching operating at the external synchronized mode is detected to the rising edge of the input signal. At the time of switching operation from standby or asynchronous to synchronous operation, it has set a delay time approx 5 s to 10 s in order to prevent malfunctions. (Fig. 3.) High EN/SYNC pin Low ON SW pin OFF Standby Delay Time External Clock Synchronization Fig. 3. Switching Operation by External Synchronized Clock Ver.2016-01-25 - 15 - NJW4170 NJW4170Application Manual Technical Information Application Information Inductors Because a large current flows to the inductor, you should select the inductor with the large current capacity not to saturate. Optimized inductor value is determined by the input voltage and output voltage. Reducing L decreases the size of the inductor. However a peak current increases and adversely affects the efficiency. (Fig. 4.) Moreover, you should be aware that the output current is limited because it becomes easy to operating to the overcurrent limit. The peak current is decided the following formula. IL Ipk VIN VOUT VOUT [A] L VIN fOSC IL [A] 2 IOUT Current Peak Current IPK Indunctor Ripple Current IL Peak Current IPK Output Current IOUT Indunctor Ripple Current IL 0 tON tOFF Reducing L Value tON tOFF Increasing L value Fig. 4. Inductor Current State Transition (Continuous Conduction Mode) - 16 - Ver.2016-01-25 NJW4170 Application Manual NJW4170 Technical Information Application Information (Continued) Input Capacitor Transient current flows into the input section of a switching regulator responsive to frequency. If the power supply impedance provided to the power supply circuit is large, it will not be possible to take advantage of the NJW4170 performance due to input voltage fluctuation. Therefore insert an input capacitor as close to the MOSFET as possible. A ceramic capacitor is the optimal for input capacitor. The effective input current can be expressed by the following formula. IRMS VOUT IOUT VIN VIN VOUT [A] In the above formula, the maximum current is obtained when VIN = 2 VOUT, and the result in this case is IRMS = IOUT (MAX) 2. When selecting the input capacitor, carry out an evaluation based on the application, and use a capacitor that has adequate margin. Output Capacitor An output capacitor stores power from the inductor, and stabilizes voltage provided to the output. Because NJW4170 corresponds to the output capacitor of low ESR, the ceramic capacitor is the optimal for compensation. In addition, you should consider varied characteristics of capacitor (a frequency characteristic, a temperature characteristic, a DC bias characteristic and so on) and unevenness peculiar to a capacitor supplier enough. Therefore when selecting a capacitors, you should confirm the characteristics with supplier datasheets. When selecting an output capacitor, you must consider Equivalent Series Resistance (ESR) characteristics, ripple current, and breakdown voltage. The output ripple noise can be expressed by the following formula. Vripple( p p) IL ESR 1 8 fOSC C OUT [V] The effective ripple current that flows in a capacitor (Irms) is obtained by the following equation. Irms Ver.2016-01-25 IL 2 3 [ Arms] - 17 - NJW4170 NJW4170Application Manual Technical Information Application Information (Continued) Catch Diode When the switch element is in OFF cycle, power stored in the inductor flows via the catch diode to the output capacitor. Therefore during each cycle current flows to the diode in response to load current. Because diode's forward saturation voltage and current accumulation cause power loss, a Schottky Barrier Diode (SBD), which has a low forward saturation voltage, is ideal. An SBD also has a short reverse recovery time. If the reverse recovery time is long, through current flows when the switching transistor transitions from OFF cycle to ON cycle. This current may lower efficiency and affect such factors as noise generation. Setting Output Voltage, Compensation Capacitor The output voltage VOUT is determined by the relative resistances of R1, R2. The current that flows in R1, R2 must be a value that can ignore the bias current that flows in ER AMP. R2 R1 VOUT 1 VB [ V ] The zero points are formed with R2 and CFB, and it makes for the phase compensation of NJW4170. The zero point is shown the following formula. f Z1 2 1 [Hz] R 2 C FB You should set the zero point as a guide from 60kHz to 80kHz. - 18 - Ver.2016-01-25 NJW4170 Application Manual NJW4170 Technical Information Application Information (Continued) Board Layout In the switching regulator application, because the current flow corresponds to the oscillating frequency, the substrate (PCB) layout becomes an important. You should attempt the transition voltage decrease by making a current loop area minimize as much as possible. Therefore, you should make a current flowing line thick and short as much as possible. Fig.5. shows a current loop at step-down converter. Especially, should lay out high priority the loop of CIN-SW-SBD that occurs rapid current change in the switching. It is effective in reducing noise spikes caused by parasitic inductance. NJW4170 Built-in SW VIN CIN NJW4170 Built-in SW L SBD COUT VIN CIN (a) Buck Converter SW ON L SBD COUT (b) Buck Converter SW OFF Fig. 5. Current Loop at Buck Converter Concerning the GND line, it is preferred to separate the power system and the signal system, and use single ground point. The voltage sensing feedback line should be as far away as possible from the inductance. Because this line has high impedance, it is laid out to avoid the influence noise caused by flux leaked from the inductance. Fig. 6. shows example of wiring at buck converter. Fig. 7 shows the PCB layout example. L V+ VIN VOUT SW CIN SBD COUT RL The capacitor is connected near an IC. NJW4170 CFB INR2 GND Separate Digital(Signal) GND from Power GND R1 To avoid the influence of the voltage drop, the output voltage should be detected near the load. Because IN- pin is high impedance, the voltage detection resistance: R1/R2 is put as much as possible near IC(IN-). Fig. 6. Board Layout at Buck Converter Ver.2016-01-25 - 19 - NJW4170 NJW4170Application Manual Technical Information Application Information (Continued) GNDOUT VOUT Power GND Area COUT GND IN L SBD CIN1 VIN CIN2 Feed back signal 1pin R2 EN/SYNC R1 RFB CFB Signal GND Area Connect Signal GND line and Power GND line on backside pattern Fig. 7. Layout Example (upper view) - 20 - Ver.2016-01-25 NJW4170 Application Manual NJW4170 Technical Information Calculation of Package Power A lot of the power consumption of buck converter occurs from the internal switching element (Power MOSFET). Power consumption of NJW4170 is roughly estimated as follows. Input Power: Output Power: Diode Loss: NJW4170 Power Consumption: Where: VIN VOUT VF OFF duty PIN = VIN IIN [W] POUT = VOUT IOUT [W] PDIODE = VF IL(avg) OFF duty [W] PLOSS = PIN POUT PDIODE [W] : Input Voltage for Converter : Output Voltage of Converter : Diode's Forward Saturation Voltage : Switch OFF Duty IIN IOUT IL(avg) : Input Current for Converter : Output Current of Converter : Inductor Average Current Efficiency ( ) is calculated as follows. = (POUT PIN) 100 [%] You should consider temperature derating to the calculated power consumption: PD. You should design power consumption in rated range referring to the power dissipation vs. ambient temperature characteristics. Ver.2016-01-25 - 21 - NJW4170 NJW4170Application Manual Technical Information Application Design Examples Buck Converter Application Circuit IC : NJW4170U2 Input Voltage : VIN=12V Output Voltage : VOUT=5V Output Current : IOUT=1A Oscillating frequency : A version fOSC=2.4MHz : B version fOSC=2.1MHz L 3.3 H/2.33A VIN=12V CIN 10mF/50V V+ VOUT=5V CFB 120pF SW R2 16kW NJW4170 EN/ SYNC GND IN- SBD COUT 22mF/6.3V R1 3kW EN/SYNC High: ON Low: OFF (Standby) Reference IC L SBD CIN COUT CFB R1 R2 - 22 - Qty. 1 1 1 1 1 1 1 1 Part Number NJW4170U2 VLF504015MT-3R3M CMS16 UMK325BJ106MM GRM31CB30J226ME18 120pF 3k 16k Description Internal 1A MOSFET SW.REG. IC Inductor 3.3 H, 2.33A Schottky Diode 40V, 3A Ceramic Capacitor 3225 10 F, 50V, X5R Ceramic Capacitor 3216 22 F, 6.3V, B Ceramic Capacitor 1608 120pF, 50V, CH Resistor 1608 3k , 1%, 0.1W Resistor 1608 16k , 1%, 0.1W Manufacturer New JRC TDK Toshiba Taiyo Yuden Murata Std. Std. Std. Ver.2016-01-25 NJW4170 Application Manual NJW4170 Technical Information Application Characteristics A version Efficiency vs. Output Current (VOUT=5V, Ta=25ºC) f=2.4MHz L=3.3 H 90 6 80 (%) 70 VIN=18V Efficiency : 60 VIN=12V 50 f=2.4MHz L=3.3 H 5.8 VIN=8V 40 30 20 Output Voltage :VOUT (V) 100 Output Voltage vs. Output Current (Ta=25ºC) 5.6 5.4 5.2 VIN=8V, 12V, 18V 5 4.8 4.6 4.4 4.2 10 4 0 1 10 100 Output Current :IOUT (mA) 1 1000 10 100 Output Current :IOUT (mA) 1000 B version Efficiency vs. Output Current (VOUT=5V, Ta=25ºC) f=2.1MHz L=3.3 H 90 Efficiency : (%) 80 70 6 VIN=18V 60 VIN=12V 50 f=2.4MHz L=3.3 H 5.8 VIN=8V Output Voltage :VOUT (V) 100 Output Voltage vs. Output Current (Ta=25ºC) 40 30 20 10 5.6 5.4 5.2 VIN=8V, 12V, 18V 5 4.8 4.6 4.4 4.2 0 4 1 Ver.2016-01-25 10 100 Output Current :IOUT (mA) 1000 1 10 100 Output Current :IOUT (mA) 1000 - 23 - NJW4170 MEMO [CAUTION] The specifications on this databook are only given for information , without any guarantee as regards either mistakes or omissions. The application circuits in this databook are described only to show representative usages of the product and not intended for the guarantee or permission of any right including the industrial rights. - 24 - Ver.2016-01-25