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FDMF8704 High Current / High Frequency FET plus Driver Multi-chip Module
November 2007
FDMF8704
Benefits
Fully optimized system efficiency. Higher efficiency levels are achievable compared with conventional discrete components. Space savings of up to 50% PCB versus discrete solutions. Higher frequency of operation. Simpler system design and board layout. Reduced time in component selection and optimization.
tm
High Current / High Frequency FET plus Driver Multi-chip Module
General Description
The FDMF8704 is a fully optimized integrated Driver plus MOSFET power stage solution for high current synchronous buck DC-DC applications. The device integrates a driver IC and two Power MOSFETs into a space saving, MLP 8x8, 56-pin package. Fairchild Semiconductor's integrated approach optimizes the complete switching power stage with regards to driver to FET dynamic performance, system inductance and overall solution ON resistance. Package parasitics and problematical layouts associated with conventional discrete solutions are greatly reduced. This integrated approach results in significant board space saving, therefore maximizing footprint power density. This solution is based on the IntelTM DrMOS specification.
Features
7V to 20V Input Voltage Range Output current to 32A 1MHz switching frequency capable Internal adaptive gate drive Low Side FET with Integrated Schottky Diode Peak Efficiency >90% Output disable for lost phase shutdown Low profile SMD package RoHS Compliant
Applications
Desktop and server VR11.x V-core and non V-core buck converters. CPU/GPU power train in game consoles and high end desktop systems. High-current DC-DC Point of Load (POL) converters. Networking and telecom microprocessor voltage regulators. Small form factor voltage regulator modules.
Powertrain Application Circuit
5V 7 - 20V CVIN VIN DISB PWM Input DISB VCIN BOOT HSEN PWM CGND VSWH PGND COUT CBOOT OUTPUT CVCIN
Figure 1. Powertrain Application Circuit
Ordering Information
Current Rating Max [A] 32 Input Voltage Typical [V] 12-19 Frequency Max [KHz] 1000 Device Marking FDMF8704
Part FDMF8704
(c)2007 Fairchild Semiconductor Corporation
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FDMF8704 Rev. F2
FDMF8704 High Current / High Frequency FET plus Driver Multi-chip Module
Pin Configuration
CGND HSEN NC VCIN BOOT CGND NC VIN VIN TEST PAD 1 VIN VIN VIN VIN 1 PWM 56 DISB NC NC NC CGND VSWH VSWH VSWH VSWH VSWH VSWH VSWH VSWH 43 14 15 VIN VIN VIN VIN VIN VIN VSWH PGND PGND PGND PGND PGND PGND 28 PGND 29 A (CGND) B (VIN) C (VSWH) 42 Figure 2. MLP 8x8 56L Bottom View
Pin Description
Pin
1, 6, 51, A 2 3, 7, 52-54 4 5 21, 40-50, C 8, 9, 11-20, B 10 22-38 39 55 56
Name
CGND HSEN NC VCIN BOOT VSWH VIN TEST PAD 1 PGND TEST PAD 2 DISB PWM IC Ground. Ground return for driver IC.
High Side FET Enable. Must be connected to BOOT pin. No connect IC Supply. +5V chip bias power. Bypass with a 1F ceramic capacitor. Bootstrap Supply Input. Provides voltage supply to high-side MOSFET driver. Connect bootstrap capacitor. Switch Node Input. SW Provides return for high-side bootstrapped driver and acts as a sense point for the adaptive shoot-thru protection. Power Input. Output stage supply voltage. For manufacturing test only. HDRV pin. This pin must be floated. Must not be connected to any pin. Power ground. Output stage ground. Source pin of low side MOSFET(s). For manufacturing test only. LDRV pin. This pin must be floated. Must not be connected to any pin. Output Disable. When low, this pin disable FET switching (HDRV and LDRV are held low). PWM Signal Input. This pin accepts a logic-level PWM signal from the controller.
VSWH VSWH VSWH TEST PAD 2 PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND
Function
FDMF8704 Rev. F2
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FDMF8704 High Current / High Frequency FET plus Driver Multi-chip Module
Absolute Maximum Rating
Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum ratings are stress ratings only.
Parameter
VCIN, PWM, DISB to PGND VIN to PGND BOOT to VSWH VSWH to PGND BOOT to PGND IO(AV) IO(PK) RJPCB PD VIN = 12V, VO = 1.3V, fsw = 1MHz, TPCB = 100C VIN = 12V, tPULSE = 10s Junction to PCB Thermal Resistance (note 1) TPCB = 100C (note 1)
Min.
-0.3 -0.3 -0.3 -1.0 -0.3
Max.
6 24 6 24 30 32 65 5 10
Units
V V V V V A A C/W W C
Operating and Storage Junction Temperature Range
-55
150
Note 1: Package power dissipation based on 4 layers, 2 square inch, 2 oz. copper pad. RJPCB is the steady state junction to PCB thermal resistance with PCB temperature referenced at VSWH pin.
Recommended Operating Range
The Recommended Operating Conditions table defines the conditions for actual device operation. Recommended operating conditions are specified to ensure optimal performance to the datasheet specifications. Fairchild does not recommend exceeding them or designing to Absolute Maximum Ratings.
Parameter
VCIN VIN VOUT Control Circuit Supply Voltage Output Stage Supply Voltage Output Voltage
Min.
4.5 7 0.8
Typ.
5 12 1.3
Max.
5.5 20 3.2
Units
V V V
Electrical Characteristics
VIN = 12V, VCIN = 5V, TA = 25C unless otherwise noted.
Parameter
Operating Voltage Range Control Circuit Supply Current PWM Input High Voltage PWM Input Low Voltage PWM Input Current DISB Input High Voltage DISB Input Low Voltage DISB Input Current
Symbol
VCIN ICC VIH(PWM) VIL(PWM) IIL(PWM) VIHDISB) VIL(DISB) IIL(DISB) tPDL(DISB-LDRV)(2) tPDH(DISB-LDRV)(2) tPDL(LDRV)(2) tPDL(HDRV)(2) tPDH(LDRV)(2) tPDH(HDRV)(2)
Conditions
fSW = 0Hz, VDISB = 0V fSW = 1MHz, VDISB = 5V
Min.
4.5
Typ.
5 1 50
Max.
5.5 3
Units
V mA V
2.4 0.8 -2 2.4 0.8 -2 8 6 VIN = 12V, VOUT = 1.3V, fsw = 1MHz, IO = 30A 9 22 12 20 2 2
V A V V A ns ns ns ns ns ns
Propagation Delay
Note 2: tPDL(LDRV/HRDV) refers to HIGH-to-LOW transition, tPDH(LDRV/HDRV) refers to LOW-to-HIGH transition.
FDMF8704 Rev. F2
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FDMF8704 High Current / High Frequency FET plus Driver Multi-chip Module
Functional Block Diagram
HSEN VCIN Q1 DISB PWM BOOT HDRV VIN
VSWH Q2 VCIN
CGND Figure 3. Functional Block Diagram
LDRV
PGND
Functional Description
The FDMF8704 is a driver plus FET module optimized for synchronous buck converter topology. A single PWM input signal is all that is required to properly drive the high-side and the low-side MOSFETs. Each part is capable of driving speeds up to 1MHz.
Adaptive Gate Drive Circuit
The driver IC embodies an advanced design that ensures minimum MOSFET dead-time while eliminating potential shootthrough (cross-conduction) currents. It senses the state of the MOSFETs and adjusts the gate drive, adaptively, to ensure they do not conduct simultaneously. Refer to Figure 4 and 5 for the relevant timing waveforms. To prevent overlap during the lowto-high switching transition (Q2 OFF to Q1 ON), the adaptive circuitry monitors the voltage at the LDRV pin. When the PWM signal goes HIGH, Q2 will begin to turn OFF after some propagation delay (tPDL(LDRV)). Once the LDRV pin is discharged below ~1.2V, Q1 begins to turn ON after adaptive delay tPDH(HDRV). To preclude overlap during the high-to-low transition (Q1 OFF to Q2 ON), the adaptive circuitry monitors the voltage at the SW pin. When the PWM signal goes LOW, Q1 will begin to turn OFF after some propagation delay (tPDL(HDRV)). Once the VSWH pin falls below ~2.2V, Q2 begins to turn ON after adaptive delay tPDH(LDRV). Additionally, VGS of Q1 is monitored. When VGS(Q1) is discharged below ~1.2V, a secondary adaptive delay is initiated, which results in Q2 being driven ON after tPDH(LDRV), regardless of SW state. This function is implemented to ensure CBOOT is recharged each switching cycle, particularly for cases where the power converter is sinking current and SW voltage does not fall below the 2.2V adaptive threshold. Secondary delay tPDH(HDRV) is longer than tPDH(LDRV).
Low-Side Driver
The low-side driver (LDRV) is designed to drive a ground referenced low RDS(ON) N-channel MOSFET. The bias for LDRV is internally connected between VCIN and CGND. When the driver is enabled, the driver's output is 180 out of phase with the PWM input. When the driver is disabled (DISB = 0V), LDRV is held low.
High-Side Driver
The high-side driver (HDRV) is designed to drive a floating N-channel MOSFET. The bias voltage for the high-side driver is developed by a bootstrap supply circuit, consisting of the external diode and external bootstrap capacitor (CBOOT). During start-up, VSWH is held at PGND, allowing CBOOT to charge to VCIN through the internal diode. When the PWM input goes high, HDRV will begin to charge the high-side MOSFET's gate (Q1). During this transition, charge is removed from CBOOT and delivered to Q1's gate. As Q1 turns on, VSWH rises to VIN, forcing the BOOT pin to VIN +VC(BOOT), which provides sufficient VGS enhancement for Q1. To complete the switching cycle, Q1 is turned off by pulling HDRV to VSWH. CBOOT is then recharged to VCIN when VSWH falls to PGND. HDRV output is in phase with the PWM input. When the driver is disabled, the high-side gate is held low.
FDMF8704 Rev. F2
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FDMF8704 High Current / High Frequency FET plus Driver Multi-chip Module
Timing Diagram
DISB VIH(DISB) VIL(DISB) tPDL(DISB) LDRV / HDRV Figure 4. Output Disable Timing VIH(PWM) PWM tPDL(LDRV) LDRV 1.2V tPDH(HDRV) tPDH(DISB)
VIL(PWM)
HDRV-SW
tPDL(HDRV) tPDH(LDRV)
SW 2.2V Figure 5. Adaptive Gate Drive Timing
FDMF8704 Rev. F2
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FDMF8704 High Current / High Frequency FET plus Driver Multi-chip Module
Typical Characteristics
VIN = 12V, VCIN = 5V, TA = 25C unless otherwise noted.
35 30
10 VIN = 12V VOUT = 1.3V L = 0.33uH fSW = 1MHz
8
25
15 10 5 0 0 25 50 75 100 o PCB Temperature, C 125 150
PLOSS, W VIN = 12V VOUT = 1.3V fSW = 1MHz L = 0.33uH
ILOAD, A
20
6
4
2
fSW = 500KHz
0 0 5 10 15 ILOAD, A 20 25 30
Figure 6. Safe Operating Area
Figure 7. Module Power Loss vs. Output Current
1.10 VIN = 12V VOUT = 1.3V IOUT = 30A L = 0.33uH
1.15
PLOSS (NORMALIZED)
PLOSS (NORMALIZED)
1.00
1.10
0.90
1.05
0.80
1.00
VOUT = 1.3V IOUT = 30A L = 0.33uH fSW = 1MHz 6 8 10 12 Input Voltage, V 14 16
0.70 300 400 500 600 700 800 fSW, KHz 900 1000 1100 1200
0.95
Figure 8. Power Loss vs. Switching Frequency
Figure 9. Power Loss vs. Input Voltage
1.15
1.6
PLOSS (NORMALIZED)
1.05
PLOSS (NORMALIZED)
1.10
1.4
VIN = 12V IOUT = 30A L = 0.33uH fSW = 1MHz
1.2
1.00
VIN = 12V VOUT = 1.3V IOUT = 30A L = 0.33uH fSW = 1MHz 4.5 5.0 5.5 Driver Supply Voltage, V 6.0
1.0
0.95
0.8 0.8 1.2 1.6 2.0 2.4 Output Voltage, V 2.8 3.2
Figure 10. Power Loss vs. Driver Supply Voltage
Figure 11. Power Loss vs. Output Voltage
FDMF8704 Rev. F2
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FDMF8704 High Current / High Frequency FET plus Driver Multi-chip Module
Typical Characteristics
VIN = 12V, VCIN = 5V, TA = 25C unless otherwise noted.
1.06 1.0 0.9 Driver Suppy Current , mA PLOSS (NORMALIZED) 1.04 0.8 PWM = 5V 0.7 0.6 PWM = 0V 0.5 0.4 0.0 0.2 0.4 0.6 Output Inductance, uH 0.8 1.0 -50 -25 0 25 50 Temperature, oC 75 100 125 VCIN = 5V DISB = 5V
1.02
1.00
VIN = 12V VOUT = 1.3V IOUT = 30A fSW = 1MHz
0.98
Figure 12. Power Loss vs. Output Inductance
Figure 13. Driver Supply Current vs. Temperature
50 VCIN = 5V 40
1.83 VCIN = 5V
PWM Threshold Voltage, V
Driver Suppy Current , mA
1.81
VIH
30
1.79
20
VIL
10
1.77
0 0 200 400 fSW, KHz 600 800 1000
1.75 -50 -25 0 25 50 Temperature, oC 75 100 125
Figure 14. Driver Supply Current vs. Frequency
Figure 15. PWM Threshold Voltage vs. Temperature
1.90 VCIN = 5V 1.85 VIH 1.80
DISB Threshold Voltage, V
1.75
VIL
1.70
1.65 -50 -25 0 25 50 Temperature, oC 75 100 125
Figure 16. DISB Threshold Voltage vs. Temperature
FDMF8704 Rev. F2
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FDMF8704 High Current / High Frequency FET plus Driver Multi-chip Module
Application Information
Supply Capacitor Selection
For the supply input (VCIN) of the FDMF8704, a local ceramic bypass capacitor is recommended to reduce the noise and to supply the peak current. Use at least a 1F, X7R or X5R capacitor. Keep this capacitor close to the FDMF8704 VCIN and CGND pins.
bootstrap capacitance of 100nF, X7R or X5R capacitor is adequate. The peak surge current rating of the boot diode should be checked in-circuit, since this is dependent on the equivalent impedance of the entire bootstrap circuit, including the PCB traces. Boot diode must be sized big enough to carry the forward charge current. Refer to Figure 14 for boot diode average forward current. The bootstrap diode must have low VF and low reverse current leakage. Breakdown voltage of the bootstrap diode must be greater than the BOOT to VSWH voltage.
Bootstrap Circuit
The bootstrap circuit uses a charge storage capacitor (CBOOT) and the external schottky diode, as shown in Figure 18. A
Typical Application
VIN 12V VCIN 5V VIN PWM DISB CGND VCIN BOOT HSEN VSWH PGND FDMF8704
VIN PWM DISB VCC EN PWM1 CGND
VCIN BOOT HSEN VSWH PGND FDMF8704 VOUT
PWM2 PWM Controller PWM3 PWM4 GND VIN PWM DISB Signal GND Power GND CGND VCIN BOOT HSEN VSWH PGND FDMF8704
VIN PWM DISB CGND
VCIN BOOT HSEN VSWH PGND FDMF8704
Figure 17. Typical Application
FDMF8704 Rev. F2
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FDMF8704 High Current / High Frequency FET plus Driver Multi-chip Module
Module Power Loss Measurement and Calculation
Refer to Figure 18 for module power loss testing method. Power loss calculation are as follows: (a) PIN (b) POUT (c) PLOSS = (VIN x IIN) + (VCIN x ICIN) (W) = VO x IOUT (W) = PIN - POUT (W)
2. It is critical that the VSWH copper has minimum area for lower switching noise emission. VSWH copper trace should also be wide enough for high current flow. Other signal routing path, such as PWM IN and BOOT signal, should be considered with care to avoid noise pickup from VSWH copper area. 3. Output inductor location should be as close as possible to the FDMF8704 for lower power loss due to copper trace. 4. Snubber for suppressing ringing and spiking of VSWH voltage should be placed near the FDMF8704. The resistor and capacitor need to be of proper size for power dissipation. 5. Place boot diode, ceramic bypass capacitor and boot capacitor as close to VCIN and BOOT pin of FDMF8704 in order to supply stable power. Routing width and length should also be considered 6. Use multiple Vias on each copper area to interconnect each top, inner and bottom layer to help smooth current flow and heat conduction. Vias should be relatively large and of reasonable inductance.
PCB Layout Guideline
Figure 19. shows a proper layout example of FDMF8704 and critical parts. All of high current flow path, such as VIN, VSWH, VOUT and GND copper, should be short and wide for better and stable current flow, heat radiation and system performance. Following is a guideline which the PCB designer should consider: 1. Input bypass capacitors should be close to VIN and GND pin of FDMF8704 to help reduce input current ripple component induced by switching operation. IIN VIN A CVIN VIN DISB PWM Input DISB VCIN BOOT HSEN PWM CGND VSWH PGND
ICIN A CVCIN VCIN
CBOOT
L
IOUT A VOUT COUT
V VO
Figure 18. Power Loss Measurement Block Diagram
Figure 19. Typical PCB Layout Example (Top View)
FDMF8704 Rev. F2
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FDMF8704 High Current / High Frequency FET plus Driver Multi-chip Module
Dimensional Outline and Pad layout
(DATUM A)
Bayan Lepas FIZ 11900, Penang, Malaysia
FDMF8704 Rev. F2
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FDMF8704 High Current / High Frequency FET plus Driver Multi-chip Module
TRADEMARKS
The following are registered and unregistered trademarks and service marks Fairchild Semiconductor owns or is authorized to use and is not intended to be an exhaustive list of all such trademarks. ACEx(R) Build it NowTM CorePLUSTM CROSSVOLTTM CTLTM Current Transfer LogicTM EcoSPARK(R) Fairchild(R) Fairchild Semiconductor(R) FACT Quiet SeriesTM FACT(R) FAST(R) FastvCoreTM FPSTM FRFET(R) Global Power ResourceSM Green FPSTM Green FPSTM e-SeriesTM GTOTM i-LoTM IntelliMAXTM ISOPLANARTM MegaBuckTM MICROCOUPLERTM MicroFETTM MicroPakTM MillerDriveTM Motion-SPMTM OPTOLOGIC(R) OPTOPLANAR(R)
(R)
PDP-SPMTM Power220(R)
Power247(R) POWEREDGE(R) Power-SPMTM PowerTrench(R) Programmable Active DroopTM QFET(R) QSTM QT OptoelectronicsTM Quiet SeriesTM RapidConfigureTM SMART STARTTM SPM(R) STEALTHTM SuperFETTM SuperSOTTM-3 SuperSOTTM-6
SuperSOTTM-8 SyncFETTM The Power Franchise(R)
TinyBoostTM TinyBuckTM TinyLogic(R) TINYOPTOTM TinyPowerTM TinyPWMTM TinyWireTM SerDesTM UHC(R) UniFETTM VCXTM
DISCLAIMER FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION, OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS. THESE SPECIFICATIONS DO NOT EXPAND THE TERMS OF FAIRCHILD'S WORLDWIDE TERMS AND CONDITIONS, SPECIFICALLY THE WARRANTY THEREIN, WHICH COVERS THESE PRODUCTS. LIFE SUPPORT POLICY FAIRCHILD'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.
PRODUCT STATUS DEFINITIONS Definition of Terms Datasheet Identification Advance Information Product Status Formative or In Design Definition This datasheet contains the design specifications for product development. Specifications may change in any manner without notice. This datasheet contains preliminary data; supplementary data will be published at a later date. Fairchild Semiconductor reserves the right to make changes at any time without notice to improve design. This datasheet contains final specifications. Fairchild Semiconductor reserves the right to make changes at any time without notice to improve design. This datasheet contains specifications on a product that has been discontinued by Fairchild semiconductor. The datasheet is printed for reference information only.
Rev. I31
Preliminary
First Production
No Identification Needed
Full Production
Obsolete
Not In Production
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