NCP1034 100V Synchronous PWM Buck Controller Description The NCP1034 is a high voltage PWM controller designed for high performance synchronous Buck DC/DC applications with input voltages up to 100 V. The NCP1034 drives a pair of external N-MOSFETs. The switching frequency is programmable from 25 kHz up to 500 kHz allowing the flexibility to tune for efficiency and size. A synchronization feature allows the switching frequency to be set by an external source or output a synchronization signal to multiple NCP1034 controllers. The output voltage can be precisely regulated using the internally trimmed 1.25 V reference voltage for low voltage applications. Protection features include user programmable undervoltage lockout and hiccup current limit. http://onsemi.com MARKING DIAGRAM SOIC-16 D SUFFIX CASE 751B A WL Y WW G Features * * * * * * * * * * * High Voltage Operating up to 100 V Programmable Switching Frequency up to 500 kHz 2 A Output Drive Capability Precision Reference Voltage (1.25 V) Programmable Soft-Start with Prebiased Load Capability Programmable Overcurrent Protection Programmable Undervoltage Protection Hiccup Current Limit Using MOSFET RDS(on) Sensing External Frequency Synchronization 16 Pin SOIC Package This is a Pb-Free Device * * * * * 48 V Non-Isolated DC-DC Converter Embedded Telecom Systems Networking and Computing Voltage Regulator Distributed Point of Load Power Architectures General High Voltage DC-DC Converters NCP1034D AWLYWWG = Assembly Location = Wafer Lot = Year = Work Week = Pb-Free Package PIN CONNECTIONS OCset 1 16 UVLO FB 2 15 RT Comp 3 14 GND SS/SD 4 13 OCIN SYNC 5 12 VCC PGND 6 11 VS LDRV 7 10 HDRV DRVCC 8 Applications 9 VB (Top View) ORDERING INFORMATION See detailed ordering and shipping information in the package dimensions section on page 22 of this data sheet. VIN: 48 V VCC: 12 V R4 110k C2 C3 100n 100n D1 1N4148 8 12 GND GND R10 5 10k 15 GND 4 16 1 14 R5 3k9 GND C5 220n R6 20k GND GND R7 11k GND VCC SYNC HDRV VS RT OCIN SS/SD LDRV UVLO OCSET GND GND C1B 2u2 GND 100n 10 Q1 NTD3055 L1 11 13 R8 7 10k 13 Q2 NTD24N06 VOUT 5 V @ 5 A, 200 kHz C9 C9B C9C 47 47 47 R1 16k9 R9 1k2 PGND 6 FB 2 C8 COMP 3 1n8 C6 IC1 NCP1034 (c) Semiconductor Components Industries, LLC, 2012 February, 2012 - Rev. 5 9 DRVVCC VB C1A 2u2 C4 R3 4k7 12n C7 330p Figure 1. Typical Application Circuit 1 R2 5k6 GND Publication Order Number: NCP1034/D 2 http://onsemi.com Figure 2. Internal Block Diagram OCset Comp Fb 1.25V SS/SD Rt SYNC UVLO GND 1uA POR Iocset 25k OCP OCP VBIAS 20uA Vref Error Amp SS/SD Vref R S 64uA Max 0.3V Ct Rt Oscillator Vcc UVLO PWM LowUVLO POR OCP Positive Current PWM DR Clk FAULT TONMIN Limit POR 1.25V = Vref 5V = VBIAS MKO 350ns Reset Dom Error Comparator Q Bias Generator Q AC ON FAULT VCC Delay LS R S Q AC ON VBIAS VBIAS 0.225x Iocset 0.0410x Iocset OCP Reset OCP Q Negative Output S R UV LowUVLO UV Detect UV Detect Positive Current SS/SD 0.25V FAULT High Voltage Level Shift Circuit Active Clamp AC ON OCin PGND LDrv DrvVCC Vs HDrv Vb NCP1034 NCP1034 PIN FUNCTION DESCRIPTION PIN PIN NAME 1 OCset DESCRIPTION 2 FB 3 COMP Output of error amplifier. An external resistor and capacitor network is typically connected from this pin to ground to provide loop compensation. 4 SS/SD Soft-Start / Shutdown. This pin provides user programmable soft-start function. External capacitor connected from this pin to ground sets the startup time of the output voltage. The converter can be shutdown by pulling this pin below 0.3 V. 5 SYNC The internal oscillator can be synchronized to an external clock via this pin and other IC's can be synchronized via this pin to internal oscillator. If it is not used this pin should be connected via 10 k resistor to ground. 6 PGND Power Ground. This pin serves as a separate ground for the MOSFET driver and should be connected to the system's power ground plane. 7 LDRV Output driver for low side MOSFET. 8 DRVVCC This pin provides biasing for the internal low side driver. A minimum of 0.1 F, high frequency capacitor must be connected from this pin to power ground. 9 VB This pin powers the high side driver and must be connected to a voltage higher than input voltage. A minimum of 0.1 F, high frequency capacitor must be connected from this pin to switch node. 10 HDRV 11 VS 12 VCC This pin provides power for the internal blocks of the IC. A minimum of 0.1 F, high frequency capacitor must be connected from this pin to ground. 13 OCIN Overcurrent sensing input. A serial resistor from this pin to drain of low MOSFET must be used to limit the current into this pin. 14 GND Signal ground for internal reference and control circuitry. 15 RT 16 UVLO Current limit set point. A resistor from this pin to GND will set the positive and negative current limit threshold Inverting input to the error amplifier. This pin is connected directly to the output of the regulator via resistor divider to set the output voltage and provide feedback to the error amplifier. Output driver for high side MOSFET Switch Node. This pin is connected to the source of the upper MOSFET and the drain of the lower MOSFET. This pin is return path for the upper gate driver. Connecting a resistor from this pin to ground sets the oscillator frequency. An external voltage divider is used to set the undervoltage threshold levels. http://onsemi.com 3 NCP1034 ABSOLUTE MAXIMUM RATINGS Min Max Unit FB, VUVLO, RT, OCset Rating Symbol -0.3 10 V COMP, SS/SD, SYNC, OCIN -0.3 5 V PGND NA NA V LDRV -0.3 VCC + 0.3 V DRVVCC, VCC -0.3 20 V VB VS VS + 20 V VS - 0.3 VB + 0.3 V VS -1.0 150 V GND NA NA V 20 mA HDRV OCin Input Current All voltages referenced to GND Symbol Value Unit RJA 130 C/W TA -40 to 125 C TSTG -55 to 150 C Junction Operating Temperature TJ -40 to 150 C ESD Withstand Voltage (Note 1) Human Body Model Machine Model VESD 2.0 200 kV Rating Thermal Resistance, Junction-to-Ambient Operating Ambient Temperature Range Storage Temperature Range Latchup Capability per Jedec JESD78 Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect device reliability. 1. Excluding pins Vb, VS and HDRV. TYPICAL ELECTRICAL PARAMETERS RECOMMENDED OPERATING CONDITIONS Symbol Definition Min Max Unit 100 V VIN Converting Voltage VCC Supply Voltage 10 18 V DRVCC Supply Voltage 10 18 V VB to VS Supply Voltage 10 18 V FSW Operating Frequency 25 500 kHz TJ Junction Temperature -40 125 C http://onsemi.com 4 NCP1034 ELECTRICAL CHARACTERISTICS (Unless otherwise specified, these specifications apply over VCC = 12 V, DRVVCC = VB = 12 V, -40C < TJ < 125C) Parameter Symbol Test Condition Min Typ Max Unit REFERENCE VOLTAGE Feedback Voltage VFB Accuracy FB Voltage Line Regulation 1.25 -40C < TJ < 125C -1.5 V +1.5 % 2.0 mV LREG 10 V < VCC < 18 V (Note 3) VCC Supply Current (Stat) ICC(Static) SS = 0 V, No Switching, RT = 10 k, ROCSET = 10 k 2.0 3.0 mA DRVVCC Supply Current (Stat) IC(Static) SS = 0 V, No Switching 0.1 0.3 mA VB Supply Current (Stat) IB(Static) SS = 0 V, No Switching 0.1 0.3 mA VCC-Start-Threshold VCC_UVLO (R) Supply Ramping Up 7.9 8.9 9.8 V VCC-Stop-Threshold VCC_UVLO (F) Supply Ramping Down 7.3 8.2 9.0 V SUPPLY CURRENT UNDERVOLTAGE LOCKOUT VCC-Hysteresis Supply Ramping Up and Down 0.7 V DRVCC-Start-Threshold DRVCC_UVLO (R) Supply Ramping Up 7.9 8.9 9.8 V DRVCC-Stop-Threshold DRVCC_UVLO (F) Supply Ramping Down 7.3 8.2 9.0 V DRVCC-Hysteresis Supply Ramping Up and Down 0.7 V VB-Start-Threshold VB_UVLO (R) Supply Ramping Up 7.9 8.9 9.8 V VB-Stop-Threshold VB_UVLO (F) Supply Ramping Down 7.3 8.2 9.0 V VB-Hysteresis Supply Ramping Up and Down 0.7 V Undervoltage Threshold Value UUVLO (Rising) 1.19 1.25 1.31 V Undervoltage Threshold Value UUVLO (Falling) 1.10 1.15 1.20 V 170 320 200 375 230 430 kHz OSCILLATOR FS RT = 20 k RT = 10 k Ramp Amplitude Vramp (Note 3) Min Duty Cycle Dmin FB = 2 V 0 % Min Pulse Width Dmin(ctrl) FS = 200 kHz, (Note 3) 200 ns Max Duty Cycle Dmax FS = 400 kHz, FB = 1.2 V SYNC(FS) 20% Above Free Running Frequency Frequency SYNC Frequency Range SYNC Pulse Duration SYNC High Level SYNC Low Level 2.0 V 80 % 500 kHz SYNC(pulse) 200 ns SYNC(H) 2.0 V SYNC(L) 0.8 1.6 V SYNC Input Threshold SYNC(Thre) V SYNC Input Hysteresis SYNC(Hyst) SYNC Input Impedance SYNC(ZIN) (Note 3) 16 k SYNC Output Impedance SYNC(OUT) (Note 3) 2.5 k SYNC Output Pulse Width SYNC(Pulse Width) FS = 500 kHz, (Note 3) 300 ns IFB SS = 3 V, FB = 1 V -0.1 300 mV ERROR AMPLIFIER Input Bias Current 2. Cold temperature performance is guaranteed via correlation using statistical quality control. Not tested in production. 3. Guaranteed by design but not tested in production. http://onsemi.com 5 -0.4 A NCP1034 ELECTRICAL CHARACTERISTICS (Unless otherwise specified, these specifications apply over VCC = 12 V, DRVVCC = VB = 12 V, -40C < TJ < 125C) Parameter Symbol Test Condition Min Typ Max Unit 50 100 120 A 4.0 10 ERROR AMPLIFIER Source/Sink Current I(Source/Sink) Bandwidth (Note 3) DC gain Transconductance (Note 3) MHz 55 dB gm (Note 3) 1500 3150 4000 mho Soft-Start Current ISS SS = 0 V 15 20 25 A Shutdown Output Threshold SD 0.3 0.4 V SOFT-START/SD OVERCURRENT PROTECTION OCSET Voltage VOCSET Hiccup Current IHiccup (Note 3) Hiccup(duty) IHiccup/ISS, (Note 3) LO, Drive Rise Time tr(Lo) CL = 1.5 nF (See Figure 3) 17 ns HI Drive Rise Time tr(Hi) CL = 1.5 nF (See Figure 3) 17 ns LO Drive Fall Time tf(Lo) CL = 1.5 nF (See Figure 3) 10 ns HI Drive Fall Time tf(Hi) CL = 1.5 nF (See Figure 3) 10 ns Dead Band Time tdead (See Figure 3) LO Output High Short Circuit Pulsed Current tLDRVhigh VLDRV = 0 V, PW v 10 s, TJ = 25C (Note 3) 1.4 A HI Output High Short Circuit Pulsed Current tHDRVhigh VHDRV = 0 V, PW v 10 s, TJ = 25C (Note 3) 2.2 A LO Output Low Short Circuit Pulsed Current tLDRVhigh VLDRV = DRVVCC, PW v 10 s, TJ = 25C (Note 3) 1.4 A HI Output Low Short Circuit Pulsed Current tHDRVhigh VHDRV = VB, PW v 10 s, TJ = 25C (Note 3) 2.2 A LO Output Resistor, Source RLOH Typical Value @ 25C, (Note 3) 7 12 LO Output Resistor, Sink RLOL Typical Value @ 25C, (Note 3) 2 8 HI Output Resistor, Source RHIH Typical Value @ 25C, (Note 3) 7 12 HI Output Resistor, Sink RHIL Typical Value @ 25C, (Note 3) 2 8 Hiccup Duty Cycle 1.25 V 1.0 A 5.0 % OUTPUT DRIVERS 30 60 2. Cold temperature performance is guaranteed via correlation using statistical quality control. Not tested in production. 3. Guaranteed by design but not tested in production. http://onsemi.com 6 120 ns NCP1034 tr tf 9V High-Side Driver (HDrv) 2V tr tf 9V Low-Side Driver (LDrv) 2V Deadband H to L Deadband L to H Figure 3. Definition of Rise-Fall Time and Deadband Time http://onsemi.com 7 NCP1034 TYPICAL OPERATING CHARACTERISTICS 1.3 9.0 Rising 8.9 8.8 1.28 UVLOVB (V) VB (V) 8.7 1.26 1.24 8.6 8.5 8.4 8.3 Falling 8.2 1.22 8.1 8.0 1.2 -40 -20 0 20 40 60 80 100 7.9 -40 120 0 20 40 60 TEMPERATURE (C) Figure 4. VFB Figure 5. UVLOVB 9.2 80 100 120 80 100 120 100 120 9.2 9.1 Rising 9.0 Rising 9.0 UVLODRVVCC (V) UVLOVCC (V) -20 TEMPERATURE (C) 8.8 8.6 8.4 Falling 8.9 8.8 8.7 8.6 8.5 8.4 Falling 8.3 8.2 8.2 8.0 -40 -20 0 20 40 60 80 100 8.1 -40 120 -20 0 20 40 60 TEMPERATURE (C) TEMPERATURE (C) Figure 6. UVLOVCC Figure 7. UVLODRVVCC 1.4 2.3 1.35 2.2 Rising ICC (stat) (mA) UVLO (V) 1.3 1.25 1.2 Falling 2.0 1.9 1.15 1.1 -40 2.1 -20 0 20 40 60 80 TEMPERATURE (C) 100 1.8 -40 120 -20 0 20 40 60 TEMPERATURE (C) Figure 8. UVLO Figure 9. ICC (Stat) http://onsemi.com 8 80 NCP1034 220 90 215 88 86 84 205 Dmax (%) fSW (kHz) 210 200 195 82 80 78 76 190 74 185 72 180 -40 -20 0 20 40 60 80 100 70 -40 120 -20 0 20 40 60 80 100 120 TEMPERATURE (C) TEMPERATURE (C) Figure 10. Switching Frequency @ RT = 20 kW Figure 11. Maximum Duty Cycle @ f = 400 kHz 210 4500 205 4000 3500 195 gm (mho) tonmin (ns) 200 190 185 3000 2500 180 2000 175 170 -40 -20 0 20 40 60 80 100 1500 -40 120 20 40 60 80 100 120 Figure 12. Minimum on Time Figure 13. Error Amplifier Transconductance 12 85 11 80 10 75 Low to High 9 R () 70 t (ns) 0 TEMPERATURE (C) 90 65 60 High to Low DRVVCC = VB = 10 V 8 12 V 7 55 6 50 18 V 5 45 40 -40 -20 TEMPERATURE (C) -20 0 20 40 60 80 100 4 -40 120 -20 0 20 40 60 80 100 TEMPERATURE (C) TEMPERATURE (C) Figure 14. Deadtime Figure 15. Driver Pullup Resistance http://onsemi.com 9 120 NCP1034 -0.2 4.0 -0.21 3.5 DRVVCC = VB = 10 V 2.5 12 V 18 V 2.0 -0.23 -0.24 -0.25 -0.26 -0.27 -0.28 1.5 -0.29 1.0 -40 -20 0 20 40 60 80 100 -0.3 -40 120 -20 0 20 40 60 80 100 120 TEMPERATURE (C) TEMPERATURE (C) Figure 16. Driver Pulldown Resistance Figure 17. OCP @ R8 = 10 kW, ROCIN = 10 kW 0.8 0.7 0.6 VDSLOWFET (V) R () 3.0 VDSLOWFET (V) -0.22 0.5 0.4 0.3 0.2 0.1 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (C) Figure 18. POSOCP @ R8 = 10 kW, ROCIN = 10 kW http://onsemi.com 10 120 NCP1034 Undervoltage Lock-out 500 There are four undervoltage lock-out circuits. Two of them protect external high-side and low-side drivers, the third ensures that the IC does not start until VCC is under a set threshold. The last one can be programmed by the user. It has a rising threshold at 1.25 V and a falling threshold at 1.15 V, and the user can define the undervoltage level by an external resistor divider. If the voltage is not over the threshold value, the device stops operating. The high-side driver UVLO only stops switching the high-side MOSFET Programmed falling and rising UVLO voltage can be calculated by Equations 1 and 2: 450 V UVLO,falling + 1.15 @ 1 ) R4 R5 400 f (kHz) 350 300 250 200 150 100 50 0 (eq. 1) 0 R4 R5 150 200 250 Figure 20. Frequency Dependence of Rt Value (eq. 2) Frequency Synchronization The NCP1034 can be synchronized to an external clock signal. The input synchronization signal should be a TTL logic level. The oscillator is synchronized to the rising edge of the synchronizing signal. When synchronization is used, the free running frequency must be set by the timing resistor to a frequency at least 80% of the external synchronization frequency (Example: RT = 20 k / 200 kHz and external TTL = 220 kHz). The NCP1034 can also output synchronization pulses on the SYNC pin. Pulses are generated when the internal oscillator ramp reaches the high threshold voltage. The frequency of these pulses is set by an external RT resistor. Up to five NCP1034 controllers can be connected directly to the SYNC pin, all of which are synchronized to the controller with the highest frequency. The lowest frequency must be at least 80% of the highest one. The equivalent internal circuit of the Sync pin is shown in Figure 21. Shutdown The output voltage can be disabled by pulling the SS/SD pin below 0.3 V. A small transistor can be used to pull it down as shown in Figure 19. During this time, both external MOSFETs are turned off. After the SS/SD pin is released, the IC starts its operation with a soft-start sequence. SS/SD 100 Rt (k) and V UVLO,rising + 1.25 @ 1 ) 50 SS/SD Figure 19. Shutdown Interface VBIAS Operating Frequency Selection The operating frequency is set by an external resistor connected from the Rt Pin to ground. The value of this resistor can be selected from Figure 20, which shows switching frequency versus the timing resistor value. SYNC Rt Rt Oscillator Ct Figure 21. Equivalent Connection of the Sync Pin http://onsemi.com 11 NCP1034 Figure 22 shows the part with no synchronization. In this circuit the internal clock is fixed by the external timing resistor RT. The SYNC pin can be tied to GND through a series resistor to prevent false triggering in a noisy environment. SYNC SYNC NCP1034 (Master #1) NCP1034 (Slave #1) RT RT FSW = 200 kHz 20 k SYNC 10 k (optional) FSW = 180 kHz 22 k SYNC NCP1034 NCP1034 (Slave #2) Synchronized System Frequency = 200 kHz RT RT FSW = 180 kHz 20 k FSW = 200 kHz 22 k Figure 22. Fixed Frequency Figure 24. Master Slave Synchronization Figure 23 shows the part synchronized to an external clock through the SYNC pin. The synchronization frequency can be up to 20% greater then the programmed fixed frequency (Example: RT = 20 k / 200 kHz and the SYNC input frequency can range from 200-220 kHz). The clock frequency at the SYNC pin replaces the master clock generated by the internal oscillator circuit. Pulling the SYNC pin low programs the part to run freely at the frequency programmed by RT. When pulling the SYNC pin low a 4.7 k resistor should be used. Output Voltage Output voltage can be set by an external resistor divider according to this Equation 3: V OUT + V ref @ 1 ) R1 R2 (eq. 3) Where Vref is the internal reference voltage 1.25 V. Absolute values of resistors R1 and R2 depend on compensation network type. See compensation paragraph for details. Inductor Selection TTL Logic 4.7 k (optional) The inductor selection is based on the output power, frequency, input and output voltage and efficiency requirements. High inductor values cause low current ripple, slower transient response, higher efficiency and increased size. Inductor design can be reduced to desire maximum current ripple in the inductor. It is good to have current ripple (ILmax) between 20% and 50% of the output current. For buck converter, the inductor should be chosen according to Equation 4. SYNC NCP1034 Input: = 220 kHz RT 20 k FSW = 220 kHz Figure 23. External Synchronization L+ Figure 24 shows the part operating in the master slave synchronization configuration. In this configuration all three parts are connected together through the SYNC pin in order to synchronize the system switching frequency. The RT timing resistor can be the same value for all three parts (RT = 20 k / 20 k / 20 k) which would make the highest frequency part the master, or to guarantee one part is the master the timing resistor can be slightly lower in value. (RT = 20 k / 22 k / 22 k) V OUT f @ I Lmax 1* V OUT V INmax (eq. 4) Output Capacitor Selection The output voltage ripple and transient requirements determine the output capacitor type and value. The important parameter for the selection of the output capacitor is equivalent serial resistance (ESR). If the capacitor has low ESR, it often has sufficient capacity for filtering as well as an adequate RMS current rating. http://onsemi.com 12 NCP1034 The value of the output capacitor should be calculated using the following equation: C OUT w I L 8 @ f @ V OUT * I L @ ESR P COND*HIGHFET + I 2OUT @ R DS(on) @ (eq. 5) P COND*LOWFET + I 2OUT @ R DS(on) @ 1 * For higher switching frequency, it is suitable to use multi-layer ceramic capacitor (MLCC) with very low ESR. The advantages are small size, low output voltage ripple and fast transient response. The disadvantage of MLCC type is the requirement to use a Type III compensation network. P SW + VIN C IN w @ 1* VOUT VIN (eq. 6) I RMS + I OUT @ VOUT V IN V IN (eq. 9) 2 @ t ON ) t OFF @ f @ I OUT (eq. 10) C OSS @ V IN 2 @ f 2 (eq. 11) Where COSS = CDS + CGS. Significant power dissipation is caused by the reverse recovery charge in the low-side MOSFET body diode, which conducts at dead time. This charge is needed to close the diode. The current from the input power supply flows through the high-side MOSFET to the low-side MOSFET body diode. This power dissipation can be calculated using Equation 12. Where VIN is the input voltage ripple and the recommended value is about 2% - 5% of VIN. The input capacitor must be large enough to handle the input ripple current. Its value should be calculated using Equation 7: V DS(off) P COSS + f @ V IN V OUT @ 1 * V OUT tON and tOFF times are dependent on the transistor gate. The MOSFET output capacitance loss is caused by the charging and discharging during the switching process and can be computed using Equation 11. The input capacitor is used to supply current pulses while high-side MOSFET is on. When the MOSFET is off, the input capacitor is being charged. The value of this capacitor can be selected with Equation 6: I OUT @ V IN Switching losses are depended on drain-to-source voltage at turn-off state, output current and switch-on and switch-off time as is shown by Equation 10. Input Capacitor Selection VOUT V OUT (eq. 8) P QRR + Q RR @ V IN @ f (eq. 7) V IN (eq. 12) QRR is the diode recovery charge as given in the manufacturer's datasheet. For some types of MOSFETs, this dissipation may be dominant at high input voltages. It is necessary to take care when selecting a MOSFET. An external Schottky diode across the low-side MOSFET can be used to eliminate the reverse recovery charge power loss. The Schottky diode's forward voltage should be lower than that of the body diode, and reverse recovery time (trr) should be lower then that of the body diode. The Schottky diode's capacitance loss can be calculated as shown in Equation . Power MOSFET Selection The NCP1034 uses two N-channel MOSFET's. They can be primary selected by RDS(on), maximum drain-to-source voltage and gate charge. RDS(on) impacts conductive losses and gate charge impacts switching losses. The low side MOSFET is selected primarily for conduction losses, and the high-side MOSFET is selected to reduce switching losses especially when the output voltage is less than 30% of the input voltages. The drain-to-source breakdown voltage must be higher than the maximum input voltage. Conductive power losses can be calculated using the Equations 8 and 9: P C(Schottky) + http://onsemi.com 13 C Schottky @ V IN 2 @ f 2 (eq. 13) NCP1034 tdead tdead High-Side Logic Signal Low-Side Logic Signal td(on) tf RDSmax High-Side MOSFET RDS(on)min tr td(off) tr tf RDSmax Low-Side MOSFET RDS(on)min td(on) td(off) Figure 25. MOSFETs Timing Diagram supply voltage, low side drive supply voltage and external UVLO are over the set thresholds. The soft-start capacitor is charged by 20 A current source. If POR is low, the SS/SD Pin is internally pulled to GND, which means that the NCP1034 is in a shutdown state. The SS/SD Pin voltage (0 V to 2.6 V) controls internal current source (64 A to 0 A) with negative linear characteristic. This current source injects current into the resistor (25 k) connected between the Fb pin and negative input of the error amplifier and into the external feedback resistor network. Voltage drop on these resistors is over 1.6 V, which is enough to force the error amplifier into negative saturation state and to block switching. When the soft-start pin reaches around 1.2 V (exact value depends on feedback and compensation network and on soft-start capacitor; a larger soft-start capacitor and a lower compensation capacity decrease this level) the IC starts switching. The impact of controlled current source decreases and the output voltage starts to rise. When the soft-start capacitor voltage reaches 2.6 V, the output voltage is at nominal value. The soft-start time must be at least 10 times longer than the time needed to charge the compensation network from the output of the error amplifier. If the soft-start time is not long enough, the soft-start sequence would be faster than the charging compensation network and the IC would start without slowly increasing the output voltage. The soft-start capacitance can be calculated using Equation 16. MOSFETs delays, turn-on and turn-off times must be short enough to prevent cross conduction. If not, there will be cross conduction from the input through both MOSFETs to ground. Due to this fact, the following conditions must be true: t d(on)high ) t dead u t d(off)low ) t f low t d(on)low ) t dead u t d(off)high ) t f high (eq. 14) Where tdead is the controller dead band time, td(on), tr, td(off) and tf are MOSFETs parameters. These parameters can be found in the datasheet for specific conditions. Bootstrap Circuit This circuit is used to obtain a voltage higher than the input voltage in order to switch-on high side N MOSFET. The bootstrap capacitor is charged from the IC's supply voltage through D1, when the low side MOSFET is switched-on up to the IC's supply voltage. It must have enough capacity to supply power for the high-side circuit when the high-side MOSFET is being switched on. The minimum value recommended for the bootstrap capacitor is 100 nF. Diode D1 has to be designed to withstand a reverse voltage given by the following equation: D1 VRmin + V IN * V CC (eq. 15) Soft-Start The soft-start time is set by capacitor connected between SS/SD Pin and ground. This function is used for controlling the output voltage slope and limiting startup currents. The start-up sequence initiates when Power On Ready (POR) internal signal rises to logic high level. That means the C SS + 15 @ 10 -6 @ T SS http://onsemi.com 14 (eq. 16) NCP1034 POR 5V ~2.6V SS ~1.2V 0V VOUT 64A IFB >1.6V 1.25V FB Voltage 1.25V 0V Figure 26. Soft-Start Start to Prebiased Output time, the energy is not discharged by the low-side MOSFET until the soft-start sequence crosses the programmed output voltage. The NCP1034 is able to startup into a prebiased output capacitor. The low-side MOSFET does not turn on before high-side MOSFET gets the first turn-on pulse. During this VOUT ~5V ~2.6V ~1.2V SS LDRV HDRV Figure 27. Startup to Prebiased Output Overcurrent Protection a current equal to 5% of the charging current. The capacitor continues to discharge until the voltage reaches 0.25 V, and then the IC initiates a standard soft start sequence. The recommended value for the protection resistor R8 is 10 k. The R7 resistance value can be calculated using Equation 17: The voltage drop across the low side MOSFET RDS(on) is connected through resistor R8 and into the IC though pin 13 OCin. Within the IC, this value is compared with the value programmed by resistor R7 to set the overcurrent limit. The programmed current limit is set by selecting the value of R7, which is connected between pin 1 OCset and GND. If the voltage drop is larger than the set value, the NCP1034 goes into hiccup mode. During this time, both external MOSFETs are turned off and the soft start capacitor is discharged with R7 + http://onsemi.com 15 R8 3.56 @ R DS(on) @ I pk (eq. 17) NCP1034 ~1.2V 0.3V ~1.2V ~1.9V 0.3V ~1.9V 0.3V 5V ~2.6V SS 5V ~2.6V ~1.2V ~1.2V VOUT IOUT ROUT Figure 28. Overcurrent Protection (Hi-Cup Mode) The NCP1034 provides protection of the low-side MOSFET against positive overcurrent (from output to this MOSFET). Its value can be calculated using Equation 18: I Pos + 5125 * 0.184 @ R8 R7 @ R DS(on) f P0 + 1 2 @ @ L @ C OUT (eq. 19) One zero of this LC filter is given by the output capacitance and output capacitor ESR. Its value can be calculated by using the following equation: (eq. 18) Compensation Circuit f Z0 + The NCP1034 is a voltage mode buck convertor with a transconductance error amplifier compensated by an external compensation network. Compensation is needed to achieve accurate output voltage regulation and fast transient response. The goal of the compensation circuit is to provide a loop gain function with the highest crossing frequency and adequate phase margin (minimally 45). The transfer function of the power stage (the output LC filter) is a double pole system. The resonance frequency of this filter is expressed as follows: 1 2 @ @ C OUT @ ESR (eq. 20) The next parameter that must be chosen is the zero crossover frequency f0. It can be chosen to be 1/10 - 1/5 of the switching frequency. These three parameters show the necessary type of compensation that can be selected from Table 1. Table 1. COMPENSATION TYPES Zero Crossover Frequency Condition Compensation Type Typical Output Capacitor Type fP0 < fZ0< f0 < fS/2 Type II (PI) Electrolytic, Tantalum fP0 < f0< fZ0 < fS/2 Type III (PID) Method I Tantalum, Ceramic fP0 < f0 < fS/2 < fZ0 Type III (PID) Method II Ceramic Compensation Type II (PI) of the switching frequency. Components of the PI compensation (Figure 29) network can be specified by the following equations: This compensation is suitable for low-cost electrolytic capacitor. The zero created by the capacitor's ESR is a few kHz and the zero crossover frequency is chosen to be 1/10 http://onsemi.com 16 NCP1034 VOUT for tantalum output capacitors, which have a higher ESR than ceramic, and its zeros and poles can be calculated shown below: R1 f Z1 + 0.75 @ f P0 - + R2 f Z2 + f P0 OTA Vref RC1 f P3 + CC2* CC1 *Optional f P2 + f 0 @ Figure 29. PI compensation (II Type) 1 * sin max 1 ) sin max 1 ) sin max ESR @ V IN @ V ref @ gm f P3 + 0.5 @ f S 1 @ R C1 @ f S V OUT * V ref R1 + @ R2 V ref The remaining calculations are the same for both methods. R C1 uu (eq. 21) C C2 + VRAMP is the peak-to-peak voltage of the oscillator ramp and gm is the transconductance error amplifier gain. Capacitor CC2 is optional. 1 2 @ @ f Z1 @ R C1 C C2 + 1 2 @ @ f P3 @ R C1 R FB1 + Tantalum and ceramics capacitors have lower ESR than electrolytic, so the zero of the output LC filter goes to a higher frequency above the zero crossover frequency. This situation needs to be compensated by the PID compensation network that is show in Figure 30. 2 gm C C1 + C FB1 + Compensation Type III (PID) 2 @ @ f 0 @ L @ V RAMP @ C OUT 1 2 @ C FB1 @ f P2 1 * R FB1 2 @ @ C FB1 @ f Z2 V ref R2 + @ R1 V OUT * V ref To check the design of this compensation network, the equation must be true C C2 R FB1 R1 @ R2 @ R FB1 R1 @ R FB1 ) R2 @ R FB1 @ R1 @ R2 R1 R C1 R2 V REF (eq. 24) V IN @ R C1 R1 + V OUT C FB1 (eq. 23) 1 * sin max f Z1 + 0.5 @ f Z2 1 0.75 @ 2 @ @ f P0 @ R C1 2 2 @ @ f 0 @ L @ V RAMP @ V OUT C C1 + fS The second one (method II) is for ceramic capacitors: f Z2 + f 0 @ R C1 + (eq. 22) f P2 + f Z0 C C1 u 1 (eq. 25) gm If it is not true, then a higher value of RC1 must be selected. Input Power Supply - OTA + The NCP1034 controller and built-in drivers need to be powered through VCC, DRVVCC and Vb pins with a voltage between 10 V - 18 V. The supply current requirement is a summation of the static and dynamic currents. Static current consumption can be calculated by the following equation: Figure 30. PID Compensation (III Type) I CS + I CC ) I C ) I B There are two methods to select the zeros and poles of compensation network. The first one (method I) is useable http://onsemi.com 17 (eq. 26) NCP1034 shunt voltage regulator and a shunt voltage regulator with transistor, as shown in Figure 31. A voltage regulator without a transistor can be used when the power consumption is low and zener diode power dissipation is acceptable. Otherwise, a shunt regulator with transistor can be used. Dynamic current consumption is calculated using the following equation, base on the switching frequency and MOSFET gate charge. I CD + Q G(low) ) Q G(high) @ f (eq. 27) To power the device, an external power supply or voltage regulator from VIN can be used. Two options are a linear VIN VIN VCC VCC R D C D Figure 31. Linear Shunt Voltage Regulator Figure 32. Shunt Voltage Regulator with Transistor For the linear shunt voltage regulator (option a) the VCC voltage is the same as the zener diode reverse voltage VZ. The value of the resistor R can be calculated using Equation 28, where IZT is the minimum reverse current at VZ. The value selected should be lower than the calculated value. The maximum power losses of resistor R and the zener diode D can be calculated by Equations 29 and 30. Rt V INmin * V CC V INmax * V CC R DC current gain. The maximum power dissipation of the resistor, zener diode and transistor are calculated by Equations 32 to 34. The transistor reverse breakdown voltage must be selected to be able to withstand the voltage difference between maximum input voltage and VCC. Rt V INmin * V ZT I )I CS * ICS CD (eq. 28) I CS ) I CD ) I ZT P R + (V INmax * V CC) @ (I CS ) I CD) PD + C P R + V INmax * V CC @ (eq. 29) (eq. 30) PD + The shunt voltage regulator with transistor (option b) is advantageous when the zener diode loss is too high or when input voltage varies across a wide range and it is difficult to set a bias point. The output voltage is lower than VZ due to the VBE of the transistor. The maximum resistor value of R can be calculated by Equation 31, where is the transistor (eq. 31) ) I ZT I CS ) I CD V INmax * V ZT I CS ) I ZT (eq. 32) @ V ZT (eq. 33) @ V ZT (eq. 34) P T + V INmax * V CC @ I CS ) I CD (eq. 35) PD + R V INmax * V ZT R * * I CS Table 2. POWER SUPPLY REGULTOR EXAMPLES MOSFETs QG(TOT) (nC) f (kHz) VINmax (V) VINmin (V) ISUPPLYmax (mA) RBIAS Components (kW) ZD Transistor LS-FET NTD24N06 24 200 60 36 8.7 2.6 MMSZ4699 - HS-FET NTD3055 7.1 LS-FET NTD24N06 24 300 60 20 16.9 10 MMSZ4699 MJD31 HS-FET NTD24N06 24 PCB Layout important, therefore, to pay close attention to the PCB layout. The layout of high-frequency and high-current switching converters has a large impact on the circuit parameters. It is http://onsemi.com 18 NCP1034 and the IC should be very short with wide traces and optimally using two layers to achieve minimum inductance between them. The blocking and bootstrap capacitors should be placed as close as possible to the IC. The feedback and compensation network should be close to the IC to minimize noise. The input capacitor, MOSFETs, inductor and output capacitor should be placed as close as possible to one another. This is suitable to reduce EMI and to minimize VS overshoots. Connecting the signal and power ground at one point near the output connector improves load regulation. Connection between the source pin of the low side MOSFET TYPICAL APPLICATION 10k R11C 10k R11D 10k R11E 10k 100n GND GND MMSZ4699 C3 GND 100n 12 5 15 GND 4 R4 110k 16 1 14 R5 3k9 R10 C5 10k 220n R6 20k C1A 2u2 D1 1N4148 C10 D2 C2 100n X1-2 C4 8 100n 9 DRVVCC VB VCC 11 VS SYNC RT OCIN SS/SD LDRV UVLO OCSET GND Q2 NTD3055 10 HDRV L1 13 R8 7 10k X2-2 13 Q3 NTD24N06 C9 C9B C9C 47 47 47 R1 16k9 PGND FB 2 C8 COMP 3 1n8 IC1 NCP1034SMD C6 4k7 X2-1 R15 12n R2 5k6 0R C7 GND GND GND GND 330p GND GND Figure 33. Single Output Buck Converter from 38 V - 58 V to 5 V/5 A @ 200 kHz 90 38 V 85 80 EFFICIENCY (%) GND 48 V VIN = 58 V 75 70 65 60 55 50 0 0.5 1 R9 1k2 6 R3 R7 10k C1B 2u2 1.5 2 2.5 3 3.5 4 4.5 5 IOUT (A) Figure 34. Efficiency and Power Loss of Circuit at Figure 33 http://onsemi.com 19 5V@5A, 200kHz R11B GND 10k 48 V $20% X1-1 R11A NCP1034 Bill of Materials Manufacturer Manufacturer Part Number 1206 Vishay CRCW10261K20FKEA 1% 1206 Vishay CRCW10263K90FKEA 1% 1206 Vishay CRCW10264K60FKEA 5k6 1% 1206 Vishay CRCW10265K60FKEA Resistor 16k9 1% 1206 Vishay CRCW102616K9FKEA 1 Resistor 20k 1% 1206 Vishay CRCW102620K0FKEA R11A, R11B, R11C, R11D, R11E 5 Resistor 12k 1% 1206 Vishay CRCW102612K0FKEA R4 1 Resistor 110k 1% 1206 Vishay CRCW1206110KFKEA R7, R8, R10 3 Resistor 10k 1% 1206 Vishay CRCW120610K0FKEA C8 1 Ceramic Capacitor 1n8 10% 1206 Kemet C1206C182K5FA-TU C6 1 Ceramic Capacitor 12n 10% 1206 Kemet C1206C123K5FACTU C5 1 Ceramic Capacitor 220n 10% 1206 Kemet C1206C224K5RACTU C7 1 Ceramic Capacitor 330p 10% 1206 Kemet - C2, C3, C4, C10 4 Ceramic Capacitor 100n 10% 1206 Kemet C1206F104K1RACTU C9A, C9B, C9C 3 Ceramic Capacitor 47/6.3V 20% 1210 Kemet C1210C476M9PAC7800 C1A, C1B 2 Ceramic Capacitor 2.2/100V 10% 1210 Murata GRM32ER72A225KA35L Designator Qty Description Value Tolerance Footprint R9 1 Resistor 1k2 1% R5 1 Resistor 3k9 R3 1 Resistor 4k7 R2 1 Resistor R1 1 R6 L1 1 Inductor SMD 13 20% 13x13 Wurth 744355131 D1 1 Switching Diode MMSD4148 - SOD123 ON Semiconductor MMSD4148T1G D2 1 Zener Diode 12V MMSZ4699 - SOD123 ON Semiconductor MMSZ4699T1G Q2 1 Power N-MOSFET NTD3055 - DPAK ON Semiconductor NTD3055-150G Q3 1 Power N-MOSFET NTD24N06 - DPAK ON Semiconductor NTD24N06T4G IO1 1 Synchronous PWM Buck Controller NCP1034 - SOIC16 ON Semiconductor NCP1034DR2G http://onsemi.com 20 NCP1034 Figure 35. Top Layer Figure 36. Bottom Layer Figure 37. Top Side Components Figure 38. Bottom Side Components http://onsemi.com 21 70 mm_ NCP1034 44 mm_ Figure 39. Typical Application Board Photos ORDERING INFORMATION Device NCP1034DR2G Package Shipping SOIC-16 (Pb-Free) 2500 / Tape & Reel For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging Specifications Brochure, BRD8011/D. http://onsemi.com 22 NCP1034 PACKAGE DIMENSIONS SOIC-16 CASE 751B-05 ISSUE K -A- 16 9 1 8 -B- P NOTES: 1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982. 2. CONTROLLING DIMENSION: MILLIMETER. 3. DIMENSIONS A AND B DO NOT INCLUDE MOLD PROTRUSION. 4. MAXIMUM MOLD PROTRUSION 0.15 (0.006) PER SIDE. 5. DIMENSION D DOES NOT INCLUDE DAMBAR PROTRUSION. ALLOWABLE DAMBAR PROTRUSION SHALL BE 0.127 (0.005) TOTAL IN EXCESS OF THE D DIMENSION AT MAXIMUM MATERIAL CONDITION. 8 PL 0.25 (0.010) B M S DIM A B C D F G J K M P R G R K F X 45 _ C -T- SEATING PLANE J M D MILLIMETERS MIN MAX 9.80 10.00 3.80 4.00 1.35 1.75 0.35 0.49 0.40 1.25 1.27 BSC 0.19 0.25 0.10 0.25 0_ 7_ 5.80 6.20 0.25 0.50 INCHES MIN MAX 0.386 0.393 0.150 0.157 0.054 0.068 0.014 0.019 0.016 0.049 0.050 BSC 0.008 0.009 0.004 0.009 0_ 7_ 0.229 0.244 0.010 0.019 16 PL 0.25 (0.010) M T B S A S SOLDERING FOOTPRINT* 8X 6.40 16X 1.12 1 16 16X 0.58 1.27 PITCH 8 9 DIMENSIONS: MILLIMETERS *For additional information on our Pb-Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting Techniques Reference Manual, SOLDERRM/D. ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice to any products herein. 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