NCP81381 Integrated Driver and MOSFET The NCP81381 integrates a MOSFET driver, high−side MOSFET and low−side MOSFET into a single package. The driver and MOSFETs have been optimized for high−current DC−DC buck power conversion applications. The NCP81381 integrated solution greatly reduces package parasitics and board space compared to a discrete component solution. www.onsemi.com MARKING DIAGRAM Features Capable of Average Currents up to 25 A Capable of Switching at Frequencies up to 2 MHz Capable of Peak Currents up to 60 A Compatible with 3.3 V or 5 V PWM Input Responds Properly to 3−level PWM Inputs Option for Zero Cross Detection with 3−level PWM ZCD_EN Input for Diode Emulation with 2−level PWM Internal Bootstrap Diode Undervoltage Lockout Supports Intel® Power State 4 Thermal Warning output Thermal Shutdown This is a Pb−Free Device 1 36 A L Y W G = Assembly Location = Wafer Lot = Year = Work Week = Pb−Free Package (Note: Microdot may be in either location) VCC CGND PWM SMOD# DISB# THWN 5 4 3 2 1 PINOUT DIAGRAM VCCD 7 GL 8 Applications • Desktop & Notebook Microprocessors GL 9 GL 10 GL 11 VSW 12 VIN 36 ZCD_EN 35 BOOT 34 PHASED 31 PGND 30 VIN VSW 13 VSW 14 SMOD from controller SMOD# CGND PHASED PHASEF VSW PGND 27 VIN 26 VIN VSW 17 VSW 18 DISB# PWM PGND 25 VIN VOUT PGND 24 PWM from controller ZCD_EN 29 VIN 28 VIN 37 VSW 15 VSW 16 PGND 23 Zero Current Detect Enable DRVON from controller VIN THWN BOOT PGND 19 PGND 20 VCCD VCC 33 GH 32 PHASEF 38 TEST PGND 21 PGND 22 5V 81381 ALYWG G QFN36 6x4 CASE 485DZ 6 • • • • • • • • • • • • • (Top View) Figure 1. Application Schematic ORDERING INFORMATION Device Package Shipping† NCP81381MNTXG QFN36 (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 Specification Brochure, BRD8011/D. © Semiconductor Components Industries, LLC, 2015 November, 2015 − Rev. 1 1 Publication Order Number: NCP81381/D NCP81381 VCCD 7 35 BOOT 33 GH 25 − 30 VIN VCC 6 LEVEL SHIFT UVLO VCC 12 − 18 VSW 32 PHASEF 34 PHASED SMOD# 3 DEAD TIME CONTROL PWM 4 SHUTDOWN TEMP WARNING SENSE LOGIC 19 PGND 20 PGND 21 PGND DISB# 2 22 PGND LEVEL SHIFT 23 PGND 24 PGND 31 PGND THWN 1 37 PGND VCC 11 GL 10 GL ZCD CONTROL ZCD_EN 36 CGND 5 9 GL 8 GL 38 TEST Figure 2. Block Diagram PIN LIST AND DESCRIPTIONS Pin No. Symbol 1 THWN Thermal warning indicator. This is an open−drain output. When the temperature at the driver die reaches TTHWN, this pin is pulled low. 2 DISB# Output disable pin. When this pin is pulled to a logic high level, the driver is enabled. There is an internal pull−down resistor on this pin. 3 SMOD# Skip Mode pin. 3−state input (see Table 1 LOGIC TABLE): SMOD# = High ³ States of ZCD_EN and PWM determine whether the NCP81381 performs ZCD or not. SMOD# = Mid ³ Connects PWM to internal resistor divider placing a bias voltage on PWM pin. Otherwise, logic is equivalent to SMOD# in the high state. SMOD# = Low ³ Placing PWM into mid−state pulls GH and GL low without delay. There is an internal pull−up resistor to VCC on this pin. Description 4 PWM PWM Control Input and Zero Current Detection Enable 5 CGND Signal Ground 6 VCC 7 VCCD Control Power Supply Input 8 GL Low Side FET Gate Access 9 GL Low Side FET Gate Access 10 GL Low Side FET Gate Access 11 GL Low Side FET Gate Access 12 VSW Switch Node Output 13 VSW Switch Node Output 14 VSW Switch Node Output 15 VSW Switch Node Output 16 VSW Switch Node Output 17 VSW Switch Node Output 18 VSW Switch Node Output Driver Power Supply Input www.onsemi.com 2 NCP81381 PIN LIST AND DESCRIPTIONS (continued) Pin No. Symbol 19 PGND Power Ground 20 PGND Power Ground 21 PGND Power Ground 22 PGND Power Ground 23 PGND Power Ground 24 PGND Power Ground 25 VIN Conversion Supply Power Input 26 VIN Conversion Supply Power Input 27 VIN Conversion Supply Power Input 28 VIN Conversion Supply Power Input 29 VIN Conversion Supply Power Input 30 VIN Conversion Supply Power Input 31 PGND 32 PHASEF 33 GH 34 PHASED Description Power Ground Bootstrap Capacitor Return (must be connected to PHASED) High Side FET Gate Access Driver Phase Connection (must be connected to PHASEF) 35 BOOT 36 ZCD_EN Bootstrap Voltage 37 PGND Power Ground 38 TEST No connection should be made to this pin. No pad is needed on the PCB footprint PWM drive logic and zero current detection enable. 3−state input: PWM = High ³ GH is high, GL is low. PWM = Mid ³ Diode emulation mode. PWM = Low ³ GH is low. State of GL is dependent on states of SMOD# and ZCD_EN (see Table 1 LOGIC TABLE). ABSOLUTE MAXIMUM RATINGS (Electrical Information − all signals referenced to PGND unless noted otherwise) (Note 1) Pin Name Min Max Unit VCC, VCCD −0.3 6.5 V GH to PHASED (DC) −0.3 VBOOT − VSW + 0.3 V GH to PHASED (< 50 ns) −5 7.7 V VIN −0.3 30 V BOOT (DC) −0.3 35 V BOOT (< 20 ns) −0.3 40 V BOOT to PHASED (DC) −0.3 6.5 V VSW, PHASED, PHASEF (DC) −0.3 30 V −5 37 V −0.3 VSW, PHASED, PHASEF (< 5 ns) All Other Pins VVCC + 0.3 V Single−Pulse Drain−to−Source Avalanche Energy, High−Side FET (TJ = 25°C, VGS = 5 V, L = 0.1 mH, RG = 25 W, IL = 54 APK) 144 mJ Single−Pulse Drain−to−Source Avalanche Energy, Low−Side FET (TJ = 25°C, VGS = 5 V, L = 0.3 mH, RG = 25 W, IL = 31.5 APK) 180 mJ Single−Pulse Drain−to−Source Avalanche Energy, High−Side FET (TJ = 25°C, L = 0.15 mH, IL = 90 APK, VDS dV/dt= 30 V / 2 ns) 200 mJ Single−Pulse Drain−to−Source Avalanche Energy, Low−Side FET (TJ = 25°C, L = 150 nH, IL = 90 APK, VDS dV/dt= 30 V / 4 ns) 200 mJ Stresses exceeding those listed in the Maximum Ratings table may damage the device. If any of these limits are exceeded, device functionality should not be assumed, damage may occur and reliability may be affected. 1. Absolute Maximum Ratings are not tested in production. www.onsemi.com 3 NCP81381 THERMAL INFORMATION Rating Thermal Resistance Operating Junction Temperature Range (Note 2) Symbol Value Unit qJA 22 _C/W RYJ−BT 2.0 _C/W RYJ−CT 4.0 _C/W TJ −40 to +150 _C −10 to +100 _C −40 to +150 _C 5.0 W Operating Ambient Temperature Range Maximum Storage Temperature Range TSTG Maximum Power Dissipation Moisture Sensitivity Level MSL 3 2. The maximum package power dissipation must be observed. 3. JESD 51−5 (1S2P Direct−Attach Method) with 0 LFM 4. JESD 51−7 (1S2P Direct−Attach Method) with 0 LFM RECOMMENDED OPERATING CONDITIONS Parameter Supply Voltage Range Pin Name Min Typ Max Unit VCC, VCCD 4.5 5.0 5.5 V VIN 4.5 12 20 V FSW = 1 MHz, VIN = 12 V, VOUT = 1.1 V 20 A FSW = 500 kHz, VIN = 12 V, VOUT = 1.1 V 25 A FSW = 500 kHz, VIN = 12 V, VOUT = 1.1 V, Duration = 10 ms, Period = 1 s 60 A 100 _C Conversion Voltage Continuous Output Current Peak Output Current Conditions Operating Temperature −10 Functional operation above the stresses listed in the Recommended Operating Ranges is not implied. Extended exposure to stresses beyond the Recommended Operating Ranges limits may affect device reliability. ELECTRICAL CHARACTERISTICS (VVCC = VVCCD = 5.0 V, VVIN = 12 V, VDISB# = 2.0 V, CVCCD = CVCC = 0.1 mF unless specified otherwise) Min/Max values are valid for the temperature range −10°C ≤ TA ≤ 100°C unless noted otherwise, and are guaranteed by test, design or statistical correlation. Parameter Symbol Conditions Min Typ Max Unit VCC SUPPLY CURRENT Operating DISB# = 5 V, ZCD_EN = 5 V, PWM = 400 kHz − 1 2 mA No switching, ZCD enabled DISB# = 5 V, ZCD_EN = 5 V, PWM = 0 V − − 2 mA No switching, ZCD disabled DISB# = 5 V, ZCD_EN = 0 V, PWM = 0 V − − 1.8 mA Disabled DISB# = 0 V ZCD_EN = VCC, SMOD# = VCC − 0.1 1 mA 10 13 mA − 27 40 mA 2.9 − 3.3 V 150 − − mV DISB# = 0 V ZCD_EN = VCC, SMOD# = GND DISB# = 0 V ZCD_EN = SMOD# = GND UVLO Start Threshold VUVLO VCC rising UVLO Hysteresis Product parametric performance is indicated in the Electrical Characteristics for the listed test conditions, unless otherwise noted. Product performance may not be indicated by the Electrical Characteristics if operated under different conditions. www.onsemi.com 4 NCP81381 ELECTRICAL CHARACTERISTICS (continued) (VVCC = VVCCD = 5.0 V, VVIN = 12 V, VDISB# = 2.0 V, CVCCD = CVCC = 0.1 mF unless specified otherwise) Min/Max values are valid for the temperature range −10°C ≤ TA ≤ 100°C unless noted otherwise, and are guaranteed by test, design or statistical correlation. Parameter Symbol Conditions Min Typ Max Unit VCCD SUPPLY CURRENT Operating DISB# = 5 V, ZCD_EN = 5 V, PWM = 400 kHz − − 15 mA Enabled, No switching DISB# = 5 V, PWM = 0 V, VPHASED = 0 V − 175 300 mA Disabled DISB# = 0 V − 0.1 1 mA To Ground, @ 25°C DISB# INPUT Input Resistance − 461 − kW Upper Threshold VUPPER − − 2.0 V Lower Threshold VLOWER 0.8 − − V 200 − − mV Hysteresis VUPPER – VLOWER Enable Delay Time tENABLE Time from DISB# transitioning HI to when VSW responds to PWM. − − 40 ms Disable Delay Time tDISABLE Time from DISB# transitioning LOW to when both output FETs are off. − 25 50 ns VPWM_HI 2.65 − − V Input Mid−state Voltage VPWM_MID 1.4 − 2.0 V Input Low Voltage VPWM_LO − − 0.7 V Input Resistance RPWM_HIZ SMOD# = VSMOD#_HI or VSMOD#_LO 10 − − MW Input Resistance RPWM_BIAS SMOD# = VSMOD#_MID − 63 − kW PWM Input Bias Voltage VPWM_BIAS SMOD# = VSMOD#_MID − 1.7 − V PWM INPUT Input High Voltage PWM Propagation Delay, Rising tpdlGL PWM = 2.25 V to GL = 90%; SMOD# = LOW − 25 35 ns PWM Propagation Delay, Falling tpdlGH PWM = 0.75 V to GH = 90% − 15 25 ns Exiting PWM Mid−state Propagation Delay, Mid−to−Low TPWM_EXIT_L PWM = Mid−to−Low to GL = 10%, ZCD_EN = High − 13 25 ns Exiting PWM Mid−state Propagation Delay, Mid−to−High TPWM_EXIT_H PWM = Mid−to−High to GH = 10% − 13 25 ns SMOD# INPUT VSMOD_HI 2.65 − − V VSMOD#_MID 1.4 − 2.0 V SMOD# Input Voltage Low VSMOD_LO − − 0.7 V SMOD# Input Resistance RSMOD#_UP Pull−up resistance to VCC − 440 − kW SMOD# Input Voltage High SMOD# Input Voltage Mid−state SMOD# Propagation Delay, Falling TSMOD#_PD_F SMOD# = Low to GL = 90%, PWM = Low − 26 30 ns SMOD# Propagation Delay, Rising TSMOD#_PD_R SMOD# = High to GL = 10%, ZCD_EN = High, PWM = Low − 15 30 ns ZCD_EN INPUT ZCD_EN Input Voltage High VZCD_EN_HI 2.0 − − V ZCD_EN Input Voltage Low VZCD_EN_LO − − 0.8 V ZCD_EN Hysteresis VZCD_EN_HYS − 250 − mV Product parametric performance is indicated in the Electrical Characteristics for the listed test conditions, unless otherwise noted. Product performance may not be indicated by the Electrical Characteristics if operated under different conditions. www.onsemi.com 5 NCP81381 ELECTRICAL CHARACTERISTICS (continued) (VVCC = VVCCD = 5.0 V, VVIN = 12 V, VDISB# = 2.0 V, CVCCD = CVCC = 0.1 mF unless specified otherwise) Min/Max values are valid for the temperature range −10°C ≤ TA ≤ 100°C unless noted otherwise, and are guaranteed by test, design or statistical correlation. Parameter Symbol Conditions Min Typ Max Unit to VCC − 270 − kW ZCD_EN INPUT ZCD_EN Input Resistance RZCD_EN_PU ZCD_EN Propagation Delay, Rising TZCD_EN,PD_R SMOD# = High, ZCD_EN = High to GL = 10% − 40 45 ns ZCD_EN Propagation Delay, Falling TZCD_EN,PD_F SMOD# = High, ZCD_EN = Low to GL = 90% − 25 40 ns ZCD FUNCTION Zero Cross Detect Threshold VZCD − −6.5 − mV ZCD Blanking + Debounce Time tBLNK − 330 − ns NON−OVERLAP DELAYS Non−overlap Delay, Leading Edge tpdhGH GL Falling = 1 V to GH−VSW Rising = 1 V − 13 − ns Non−overlap Delay, Trailing Edge tpdhGL GH−VSW Falling = 1 V to GL Rising = 1 V − 12 − ns TTHWN Temperature at Driver Die − 150 − °C − 15 − °C − 180 − °C TTHDN_HYS − 25 − °C ITHWN − − 5 mA − 300 − mV THERMAL WARNING & SHUTDOWN Thermal Warning Temperature Thermal Warning Hysteresis TTHWN_HYS Thermal Shutdown Temperature TTHDN Thermal Shutdown Hysteresis THWN Open Drain Current Temperature at Driver Die BOOSTSTRAP DIODE Forward Bias Current = 2.0 mA Forward Voltage Product parametric performance is indicated in the Electrical Characteristics for the listed test conditions, unless otherwise noted. Product performance may not be indicated by the Electrical Characteristics if operated under different conditions. DISB# t ENABLE t DISABLE PWM tpdl GH tpdl GL 90% GH−VSW 1V 1V tpdh GH tpdh GL 90% GL 10% 1V 1V VSW Figure 3. Timing Diagram www.onsemi.com 6 NCP81381 Table 1. LOGIC TABLE INPUT TRUTH TABLE DISB# PWM SMOD# (Note 5) ZCD_EN GH GL L X X X L L H H X X H L H L X L L L H L X H L H H MID H or MID H L ZCD (Note 6) H MID X L L L (Note 7) H MID L X L L (Note 7) 5. PWM input is driven to mid−state with internal divider resistors when SMOD# is driven to mid−state and PWM input is undriven externally. 6. GL goes low following 80 ns de−bounce time, 250 ns blanking time and then SW exceeding ZCD threshold. 7. There is no delay before GL goes low. Figure 4. Efficiency − 12 V Input, 1.2 V Output, 500 kHz Figure 5. Efficiency − 19 V Input, 1.2 V Output, 500 kHz www.onsemi.com 7 NCP81381 APPLICATIONS INFORMATION Theory of Operation Safety Timer and Overlap Protection Circuit The NCP81381 is an integrated driver and MOSFET module designed for use in a synchronous buck converter topology. The NCP81381 supports numerous application control definitions including ZCD (Zero Current Detect) with Pin enable and alternately PWM Tristate control. A PWM input signal is required to control the drive signals to the high−side and low−side integrated MOSFETs. It is important to avoid cross−conduction of the two MOSFETS which could result in a decrease in the power conversion efficiency or damage to the device. The NCP81381 prevents cross conduction by monitoring the status of the MOSFET gates and applying the appropriate amount of non−overlap time (the time between the turn−off of one MOSFET and the turn−on of the other MOSFET). When the PWM input pin is driven high, the low−side MOSFET gate (GL) starts to go low after a propagation delay (tpdlGL). The time it takes for the low−side MOSFET to turn off is dependent on the low−side MOSFET gate charge. The high−side MOSFET gate begins to rise a fixed time (tpdhGH) after the GL voltage falls below the low−side MOSFET gate threshold. When the PWM input pin is driven low, the high−side MOSFET gate (GH) starts to go low after a propagation delay (tpdlGH). The time it takes for the high−side MOSFET to turn off is dependent on the high−side MOSFET gate charge. The low−side MOSFET gate begins to rise a fixed time (tpdhGH) after the GH voltage falls below the high−side MOSFET gate threshold. Low−Side Driver The low−side driver drives an internal, ground−referenced low−RDS(on) N−Channel MOSFET. The voltage supply for the low−side driver is internally connected to the VCCD and PGND pins. High−Side Driver The high−side driver drives an internal, floating low−RDS(on) N−channel MOSFET. The gate voltage for the high side driver is developed by a bootstrap circuit referenced to Switch Node (VSW, PHASEF and PHASED) pins. The bootstrap circuit is comprised of the integrated diode and an external bootstrap capacitor and resistor. When the NCP81381 is starting up, the VSW pin is at ground, allowing the bootstrap capacitor to charge up to VCCD through the bootstrap diode (See Figure 1). When the PWM input is driven high, the high−side driver will turn on the high−side MOSFET using the stored charge of the bootstrap capacitor. As the high−side MOSFET turns on, the voltage at the VSW, PHASEF and PHASED pins rise. When the high−side MOSFET is turned fully on, the switch node will settle to VIN and the BST pin will settle to VIN + VCCD (excluding parasitic ringing). Zero Current Detect Enable Input (ZCD_EN) The ZCD_EN pin is a logic input pin with an internal pull−up resistance to VCC. When ZCD_EN is set low, the NCP81381 will operate in synchronous rectifier (PWM) mode. This means that negative current can flow in the LS MOSFET if the load current is less than ½ delta current in the inductor. When ZCD_EN is set high, Zero Current Detect PWM (ZCD_PWM) mode will be enabled With ZCD_EN set high, when PWM rises above VPWM_HI, GL will go low and GH will go high after the non−overlap delay. Subsequently, if PWM falls to less than VPWM_HI, but stays above VPWM_LO, GL will go high after the non−overlap delay, and stay high for the duration of the ZCD Blanking + Debounce time (TBLNK). Once this timer has elapsed, VSW will be monitored for zero current, and GL will be pulled low when zero current is detected. The VSW zero current threshold undergoes an auto−calibration cycle every time DISB# is brought from low to high. Bootstrap Circuit The bootstrap circuit relies on an external charge storage capacitor (CBST) and an integrated diode to provide current to the HS Driver. A multi−layer ceramic capacitor (MLCC) with a value greater than 100 nF should be used as the bootstrap capacitor. An 4 W resistor in series with CBST is recommended to decrease VSW overshoot. Power Supply Decoupling The NCP81381 will source relatively large currents into the MOSFET gates. In order to maintain a constant and stable supply voltage (VCCD) a low−ESR capacitor should be placed near the power and ground pins. A multi layer ceramic capacitor (MLCC) between 1 mF and 4.7 mF is typically used. A separate supply pin (VCC) is used to power the analog and digital circuits within the driver. A 1 mF ceramic capacitor should be placed on this pin in close proximity to the NCP81381. It is good practice to separate the VCC and VCCD decoupling capacitors with a resistor (10 W typical) to avoid coupling driver noise to the analog and digital circuits that control driver function (See Figure 1). PWM Input The PWM Input pin is a tri−state input used to control the HS MOSFET ON/OFF state. In conjunction with ZCD_EN it also determines the state of the LS MOSFET. See Table1 for logic operation. The PWM in some cases must operate with frequency programming resistances to ground. These resistances can range from 10 kW to 300 kW depending on the application. When SMOD# is set to > VSMOD#_HI or to < VSMOD#_LO, the input impedance to the PWM input is very high in order to avoid interferences with controllers that must use programming resistances on the PWM pin. www.onsemi.com 8 NCP81381 Thermal Warning/Thermal Shutdown Output If VSMOD#_LO < SMOD# < VSMOD#_HI (Mid−State), internal resistances will set undriven PWM pin voltage to Mid−State. The DISB# pin is used to disable the GH to the High−Side FET to prevent power transfer. The pin has a pull−down resistance to force a disabled state when it is left unconnected. DISB# can be driven from the output of a logic device or set high with a pull−up resistance to VCC. The THWN pin is an open drain output. When the temperature of the driver exceeds TTHWN, the THWN pin will be pulled low indicating a thermal warning. At this point, the part continues to function normally. When the temperature drops TTHWN_HYS below TTHWN, the THWN pin will go high. If the driver temperature exceeds TTHDN, the part will enter thermal shutdown and turn off both MOSFETs. Once the temperature falls TTHDN_HYS below TTHDN, the part will resume normal operation. VCC Undervoltage Lockout Skip Mode Input (SMOD#) The VCC pin is monitored by an Undervoltage Lockout Circuit (UVLO). VCC voltage above the rising threshold enables the NCP81381. The SMOD# tri−state input pin has an internal pull−up resistance to VCC. When driven high, the SMOD# pin enables the low side synchronous MOSFET to operate independently of the internal ZCD function. When the SMOD# pin is set low during the PWM cycle it disables the low side MOSFET to allow discontinuous mode operation. The NCP81381 has the capability of internally connecting a resistor divider to the PWM pin. To engage this mode, SMOD# needs to be placed into mid−state. While in SMOD# mid−state, the IC logic is equivalent to SMOD# being in the high state. Disable Input (DISB#) Table 2. UVLO/DISB# LOGIC TABLE UVLO DISB# Driver State L X Disabled (GH = GL = 0) H L Disabled (GH = GL = 0) H H Enabled (See Table x) H Open Disabled (GH = GL = 0) Inductor Current Inductor Current ZCD_EN PWM PWM GH GH GL GL 80 ns De-bounce timer ZCD waits until timers expire ZCD_EN ZCD detected 80 ns 250 ns ZCD blanking timer De-bounce timer 250 ns ZCD blanking timer Figure 6. PWM Timing Diagram NOTES: If the Zero Current Detect circuit detects zero current after the ZCD Wait timer period, the GL is driven low by the Zero Current Detect signal. If the Zero Current Detect circuit detects zero current before the ZCD Wait timer period has expired, the Zero Current detect signal is ignored and the GL is driven low at the end of the ZCD Wait timer period. www.onsemi.com 9 NCP81381 Inductor Current PWM GH SMOD# triggered GL SMOD# Figure 7. SMOD# Timing Diagram NOTE: If the SMOD# input is driven low at any time after the GL has been driven high, the SMOD# Falling edge will trigger the GL to go low. If the SMOD# input is driven low while the GH is high, the SMOD# input is ignored. Inductor Current 0 A ZCD triggered SMOD# = High SMOD# ZCD_EN PWM GH GL LS FET is off LS FET on until ZCD TZCD_BLANK + TDEBOUNCE Figure 8. ZCD_EN Timing Diagram NOTE: When ZCD is enabled by pulling ZCD_EN# high, the NCP81381 keeps the LS FET on until it detects zero current, reducing power loss. www.onsemi.com 10 NCP81381 For Use with Controllers with 3−State PWM and No Zero Current Detection Capability: Table 3. LOGIC TABLE − 3−STATE PWM CONTROLLERS WITH NO ZCD PWM SMOD# ZCD_EN GH GL H H H ON OFF M H H OFF ZCD L H H OFF ON To operate the buck converter in continuous conduction mode (CCM), PWM needs to switch between the logic high and low states. To enter into DCM, PWM needs to be switched to the mid−state. Whenever PWM transitions to mid−state, GH turns off and GL turns on. GL stays on for the duration of the de−bounce timer and ZCD blanking timers. Once these timers expire, the NCP81381 monitors the SW voltage and turns GL off when SW exceeds the ZCD threshold voltage. By turning off the LS FET, the body diode of the LS FET allows any positive current to go to zero but prevents negative current from conducting. This section describes operation with controllers that are capable of 3 states in their PWM output and relies on the NCP81381 to conduct zero current detection during discontinuous conduction mode (DCM). The SMOD# pin needs to either be set to 5 V or left disconnected. The NCP81381 has an internal pull−up resistor that connects to VCC that sets SMOD# to the logic high state if this pin is disconnected. The ZCD_EN pin needs to either be set to 5 V or left disconnected. The NCP81381 has an internal pull−up resistor connected to VCC that will set ZCD_EN to the logic high state if this pin is left disconnected. Figure 9. Timing Diagram − 3−state PWM Controller, No ZCD www.onsemi.com 11 NCP81381 For Use with Controllers with 3−state PWM and Zero Current Detection Capability: Table 4. LOGIC TABLE − 3−STATE PWM CONTROLLERS WITH ZCD PWM SMOD# ZCD_EN GH GL H L H ON OFF M L H OFF OFF L L H OFF ON To operate the buck converter in continuous conduction mode (CCM), PWM needs to switch between the logic high and low states. During DCM, the controller is responsible for detecting when zero current has occurred, and then notifying the NCP81381 to turn off the LS FET. When the controller detects zero current, it needs to set PWM to mid−state, which causes the NCP81381 to pull both GH and GL to their off states without delay. This section describes operation with controllers that are capable of 3 PWM output levels and have zero current detection during discontinuous conduction mode (DCM). The SMOD# pin needs to be pulled low (below VSMOD#_LO). The ZCD_EN pin needs to either be set to 5 V or left disconnected. There is an internal pull−up resistor that connects to VCC and sets ZCD_EN to the logic high state if this pin is left disconnected. SMOD# 0 V ZCD_EN 5 V IL 0 A SMOD# = Low ZCD_EN = High Controller detects zero current → Sets PWM to mid−state. PWM PWM in mid−state pulls GL low. GH GL Figure 10. Timing Diagram − 3−state PWM Controller, with ZCD www.onsemi.com 12 NCP81381 For Use with Controllers with 2−Level PWM and Zero Current Detection Capability: Table 5. LOGIC TABLE − 2−STATE PWM CONTROLLERS WITH ZCD PWM SMOD# ZCD_EN GH GL H L X ON OFF L L H OFF ON L L L OFF OFF When PWM is in the low state, the state of ZCD_EN determines whether the converter is placed into diode emulation mode. When the controller detects positive inductor current, ZCD_EN should be in the high state, allowing the LS FET to be on and conducting. Once the controller detects zero or negative current, ZCD_EN should be placed into the low state, turning off the LS FET. With the LS FET turned off, the body diode of the LS FET allows any positive current that may still be flowing to reach zero, but prevents the current from flowing in the negative direction. This section describes operation with controllers that do not have 3−level PWM output capability but are capable of zero current detection during discontinuous conduction mode (DCM). The SMOD# pin needs to be pulled low (below VSMOD#_LO). When PWM is high, GH will always be in the high state and GL will always be in the low state, regardless of the state ZCD_EN is in. SMOD# 0 V SMOD# = Low IL 0 A Controller detects zero current → Sets ZCD_EN low. ZCD_EN Low ZCD_EN pulls GL low. PWM GH GL Figure 11. Timing Diagram − 2−state PWM Controller, with ZCD www.onsemi.com 13 NCP81381 Recommended PCB Layout (viewed from top) INPUT BYPASS CAPS VIN VIN BOOTSTRAP RC INPUT BYPASS CAPS NCP81381 VCC BYPASS CAP GND INPUT BYPASS CAPS SNUBBER VCCD BYPASS CAP TESTPOINT VSW GND GND INDUCTOR VOUT OUTPUT BYPASS CAP OUTPUT BYPASS CAP VOUT OUTPUT BYPASS CAPS Figure 12. Top Copper Layer OUTPUT BYPASS CAPS Figure 13. Bottom Copper Layer Figure 14. Layer 2 Copper Layer (Ground Plane) www.onsemi.com 14 NCP81381 PACKAGE DIMENSIONS QFN36 6x4, 0.4P CASE 485DZ ISSUE A ÉÉ ÉÉ PIN ONE REFERENCE NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M, 1994. 2. CONTROLLING DIMENSION: MILLIMETERS. 3. DIMENSION b APPLIES TO PLATED TERMINAL AND IS MEASURED BETWEEN 0.15 AND 0.25 MM FROM THE TERMINAL TIP. 4. COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE TERMINALS. A B D E 0.15 C 2X 0.15 C 2X DIM A A1 A3 b D D2 D3 D4 D5 E E2 E3 E4 e G G1 H H1 H2 L L2 TOP VIEW (A3) A 0.10 C 0.08 C NOTE 4 A1 SIDE VIEW C SEATING PLANE D2 D4 D5 D3 7 G G1 18 H E2 E4 E3 H2 24 1 36 H1 36X BOTTOM VIEW b 0.10 M C A B 0.05 M C 30X 6X e e/2 SUPPLEMENTAL BOTTOM VIEW L NOTE 3 MILLIMETERS MIN MAX 0.90 1.20 0.00 0.05 0.20 REF 0.15 0.25 6.00 BSC 4.95 5.05 0.91 1.01 3.04 3.14 2.70 2.80 4.00 BSC 2.44 2.54 1.14 1.24 2.29 2.39 0.40 BSC 0.52 0.62 0.43 0.53 1.35 1.45 0.60 0.70 0.57 0.68 0.30 0.50 0.15 0.35 L2 RECOMMENDED SOLDERING FOOTPRINT* 6X 0.30 2.37 2.85 0.78 36X 0.25 2X 1.29 30X 1 0.60 R0.15 1.37 4.30 1.25 1.45 0.78 1.23 DETAIL A 0.63 DETAIL A 1.13 3.26 0.40 PITCH ALL SIDES *For additional information on our Pb−Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting Techniques Reference Manual, SOLDERRM/D. www.onsemi.com 15 NO EXPOSED METAL ALLOWED 0.66 NCP81381 PACKAGE DIMENSIONS QFN36 6x4, 0.4P CASE 485DZ RECOMMENDED SOLDER STENCIL Intel is a registered trademark of Intel Corporation in the U.S. and/or other countries. ON Semiconductor and the are registered trademarks of Semiconductor Components Industries, LLC (SCILLC) or its subsidiaries in the United States and/or other countries. SCILLC owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of SCILLC’s product/patent coverage may be accessed at www.onsemi.com/site/pdf/Patent−Marking.pdf. SCILLC reserves the right to make changes without further notice to any products herein. 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