Synchronous-Rectified Buck MOSFET Drivers RT9603 high frequency,
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RT9603
Synchronous-Rectified Buck MOSFET Drivers
RT9603 high frequency, dual MOSFET drivers specifically designed drive power N-MOSFETs synchronous-rectified buck converter topology. device combined with RT924x series multi-phase controllers MOSFETs form complete core voltage regulator solution advanced microprocessors. output drivers RT9603 efficiently switch power MOSFETs frequencies 500kHz. shall taken into account thermal consideration when switching frequency above 500kHz. Each driver capable driving load 30/40ns rise/fall time with fast propagation delay from input transition gate power MOSFET. device implements boot-strapping upper gate with only external capacitor diode required. This reduces implementation complexity allows higher performance, cost effective NMOSFETs. Both drivers incorporate adaptive shoot-through protection prevent upper lower MOSFETs from conducting simultaneously shorting input supply. unique feature RT9603 driver addition over-voltage protection event upper MOSFET direct shorted before power-on. RT9603 detects fault condition during initial start-up, internal poweron sense circuitry will rapidly drive output lower MOSFET before multi-phase controller takes control. result, input supply will latch into shutdown state, thereby prevent processor from damaged.
Features
Drives N-MOSFETs Adaptive Shoot-Through Protection Supports High Switching Frequency Fast Output Rise Time Propagation Delay 40ns Tri-State Input Bridge Shutdown Supply Over-Voltage Protection above Maximum Voltage Rating Supply Under-Voltage Protection Upper MOSFET Direct Shorted Protection Small SOP-8 Package RoHS Compliant 100% Lead (Pb)-Free
Applications
Core Voltage Supplies Intel Pentium® AMD® AthlonMicroprocessors High Frequency Profile DC-DC Converters High Current Voltage DC-DC Converters Equipments
Ordering Information
RT9603 Package Type SOP-8 Operating Temperature Range Free with Commercial Standard Green (Halogen Free with Commercial Standard)
Note RichTek Pb-free Green products RoHS compliant compatible with current requirements IPC/JEDEC J-STD-020. Suitable SnPb Pb-free soldering processes. 100%matte (Sn) plating.
Configurations
(TOP VIEW)
DRVH PGND DRVL
SOP-8
DS9603-08 March 2007
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RT9603
Typical Application Circuit
+12V +12V
1N4148
1000uF/16V
RT9603
DRVH DRVL
PHB95N03LT
PHB83N03LT 2.4K ISNx 2.4K x1500uF VCORE x1500uF
INPUT
PGND
ISPx
Note: traces that from controller ISPx ISNx pins, should together next each other Kelvin connected Place both close Controller possible.
Functional Description
Name Function Floating bootstrap supply upper gate drive. Connect bootstrap capacitor between this pin. bootstrap capacitor provides charge turn upper MOSFET. Accepts logic control signal. Connect this output controller. DRVL PGND DRVH signal enters remains within shutdown window, output drivers disabled both MOSFET gates pulled held low. Internal Connection. Supply Input. Connect +12V supply. Place bypass capacitor from this PGND. Lower gate drive output. Should connected lower MOSFET gate. Common Ground. Upper driver return. Should connected common node upper lower MOSFETs. voltage monitored adaptive shoot-through protection. Upper gate drive output. Should connected upper MOSFET gate.
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DS9603-08 March 2007
RT9603
Function Block Diagram
Internal Control Logic
Shoot-Through Protection DRVH Power-On Shoot-Through Protection DRVL PGND
Timing Diagram
TPDDRVH TRDRVH TFDRVH
DRVH
DRVL
TFDRVL TRDRVL TPDDRVL
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RT9603
Absolute Maximum Ratings
(Note -10V -0.3V VCC+15V -0.3V 0.3V 0.3V VBST 0.3V 0.3V VVCC 0.3V 0.625W 160°C/W 260°C -40°C 150°C 200V Supply Voltage, -BST 200ns -BST 200ns -PWM Input Voltage -DRVH -DRVL -Power Dissipation, 25°C SOP-8 -Package Thermal Resistance (Note SOP-8, -Lead Temperature (Soldering, sec.) -Storage Temperature Range -ESD Susceptibility (Note (Human Body Mode) (Machine Mode)
Recommended Operating Conditions
(Note Supply Voltage, ±10% Ambient Temperature Range 70°C Junction Temperature Range 125°C
Electrical Characteristics
(Recommended Operating Conditions, 25°C unless otherwise specified)
Parameter Supply Current Power Supply Current Power-On Reset Threshold Hysteresis Input Input Current Floating Voltage PWM_IN Threshold DRVH Rise Time DRVH Fall Time
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Symbol
Test Conditions
Units
IVCC
VBST 12V, VPWM_IN
VVCCRTH VVCCHYS IPWM_IN VPWMFL
Rising
1.35
10.7
VPWM_IN
1.26
VPWMRTH PWM_IN Rising VPWMFTH PWM_IN Falling TRDRVH TFDRVH VVCC 12V, load VVCC 12V, load
continued
DS9603-08 March 2007
RT9603
Parameter DRVL Rise Time DRVL Fall Time DRVH Turn-Off Propagation Delay DRVL Turn-Off Propagation Delay Shutdown Window Output Upper Drive Source Upper Drive Sink Lower Drive Source Lower Drive Sink RDRVH RDRVH RDRVL RDRVL VVCC VVCC VVCC VVCC Symbol TRDRVL TFDRVL TPDDRVH TPDDRVL Test Conditions VVCC= 12V, load VVCC 12V, load VVCC 12V, load VVCC 12V, load -1.0 -Typ -4.3 Units
Note Stresses beyond those listed under Absolute Maximum Ratings" cause permanent damage device. These stress ratings only, functional operation device these other conditions beyond those indicated operational sections specifications implied. Exposure absolute maximum rating conditions extended periods affect device reliability. Note Devices sensitive. Handling precaution recommended. human body model 100pF capacitor discharged through 1.5k resistor into each pin. Note device guaranteed function outside operating conditions. Note measured natural convection 25°C effective thermal conductivity test board JEDEC 51-3 thermal measurement standard.
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RT9603
Application Information
RT9603 designed drive both high side side N-MOSFET through externally input control signal. power-on protection function which held DRVH DRVL before across rising threshold voltage. After initialization, signal takes control. rising signal first forces DRVL signal turns then DRVH signal allowed high just after non-overlapping time avoid shoot-through current. falling signal first forces DRVH low. When DRVH signal reach predetermined level, DRVL signal allowed turn high. non-overlapping function also presented between DRVH DRVL signal transient. signal acted "High" above rising threshold acted "Low" below falling threshold. signal level enters remains within shutdown window considered "tri-state", output drivers disabled both MOSFET gates pulled held low. left signal (IN) floating, will kept 2.1V internal divider provide controller with recognizable level. RT9603 typically operates frequency 200kHz 250kHz. shall noted that place 1N4148 schottky diode between shown typical application circuit. Driving Power MOSFETs input impedance power MOSFET extremely high. When 5V), gate draws current only nano-amperes. Thus once gate been driven "ON" level, current could negligible. However, capacitance gate source terminal should considered. requires relatively large currents drive gate down rapidly. also required switch drain current with required speed. required gate drive currents calculated follows.
Cgd1 Igs1 Igd2 Igs2 Cgs2
+12V
Cgs1 Cgd2 Igd1
VOUT
Figure Equivalent Circuit Associated Waveforms Figure current required move gate 12V. operation consists charging Cgs. Cgs1 Cgs2 capacitances from gate source high side side power MOSFETs, respectively. general data sheets, referred "Crss" which input capacitance. Cgd1 Cgd2 capacitances from gate drain high side side power MOSFETs, respectively referred data sheets "Crss" reverse transfer capacitance. example, rising time high side side power MOSFETs respectively, required current Igs1 Igs2 showed below:
dVg1 dVg2
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DS9603-08 March 2007
RT9603
Before driving gate high side MOSFET 5V), side MOSFET off; high side MOSFET turned before side turned From Figure body diode "D2" been turned before high side MOSFETs turned Layout Consideration Figure shows schematic circuit two-phase synchronous buck converter implement RT9603. converter operates from VIN.
PHB83N03LT
lgd1
1.2uH 1000uF
Before side MOSFET turned Cgd2 have been charged VIN. Thus, Cgd2 reverses polarity charged 12V, required current
DRVH
VCORE 1500uF
RT9603
PHB95N03LT
DRVL
PGND
Figure Two-Phase Synch. Buck Converter Circuit When layout PCB, should very careful. powercircuit section most critical one. configured properly, will generate large amount EMI. junction should very close. Next, trace from DRVH, DRVL should also short decrease noise driver output signals. signals from junction power MOSFET, carrying large gate drive current pulses, should heavy gate drive trace. bypass capacitor should connected PGND directly. Furthermore, bootstrap capacitors (CB) should always placed close pins possible. Select Bootstrap Capacitor Figure shows part bootstrap circuit RT9603. (the voltage difference between RT9603) provides voltage gate high side power MOSFET. This supply needs ensured that MOSFET driven. this, capacitance selected properly. determined following constraints.
helpful calculate these currents typical case. Assume synchronous rectified buck converter, input voltage 12V, 12V. high side MOSFET PHB83N03LT whose Ciss 1660pF, Crss 380pF, 14ns. side MOSFET PHB95N03LT whose Ciss 2200pF, Crss 500pF 30ns, from equation obtain
1660
2200
1.428
0.88
from equation.
lgs1
0.326
0.4(A)
total current required from gate driving source
(1.428 0.326) 1.745(A)
(0.88 0.4) 1.28(A)
(10)
similar calculation, also sink current required from turned MOSFET.
DS9603-08 March 2007
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RT9603
1N4148
DRVH
Figure shows power dissipation RT9603 function frequency load capacitance. value same frequency varied from 100kHz 1MHz.
Power Dissipation Frequency
1000
CU=CL=3nF
Power Dissipation (mW)
DRVL PGND
1000
CU=CL=2nF
Figure Part Bootstrap Circuit RT9603 practice, value capacitor will lead overcharging that could damage Therefore minimize risk overcharging reducing ripple VCB, bootstrap capacitor should smaller than 0.1F, larger better. general design, using provide better performance. least low-ESR capacitor should used provide good local decoupling. Here, adopt either ceramic tantalum capacitor suitable. Power Dissipation exceeding maximum allowable power dissipation drive beyond maximum recommended operating junction temperature 125°C, necessary calculate power dissipation appropriately. This dissipation function switching frequency total gate charge selected MOSFET. Figure shows power dissipation test circuit. DRVH DRVL load capacitors, respectively. bootstrap capacitor value 0.01F.
+12V
1N4148
CU=CL=1nF
Frequency (kHz)
Figure Power Dissipation Frequency operating junction temperature calculated from power dissipation curves (Figure Assume VCC=12V, operating frequency 200kHz CU=CL=1nF which emulate input capacitances high side side power MOSFETs. From Figure power dissipation 100mW. RT9603, package thermal resistance 160°C/W, operating junction temperature calculated (160°C/W 100mW) 25°C 41°C where ambient temperature 25°C. method improve thermal transfer increase copper area around RT9603 first. Then, adding ground under transfer heat peripheral board. (11)
CBST
+12V
DRVH
2N7002
RT9603
2N7002 DRVL PGND
Figure Test Circuit
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DS9603-08 March 2007
RT9603
Over-Voltage Protection Function Power-On unique feature RT9603 driver addition over-voltage protection event upper MOSFET direct shorted before power-on. RT9603 detects fault condition during initial start-up, internal poweron sense circuitry will rapidly drive output lower MOSFET before multi-phase controller takes control. Figure shows measured waveforms with high side MOSFET directly shorted 12V.
DRVL VCORE
Figure Waveforms High Side MOSFET Shorted Please note that trigger point RT9603 clamped level about 2.4V. Obviously since voltage increases during initial start-up, VCORE increases correspondingly, would quickly drop-off followed DRVL decreased.
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RT9603
Outline Dimension
Dimensions Millimeters Symbol 4.801 3.810 1.346 0.330 1.194 0.170 0.050 5.791 0.400 5.004 3.988 1.753 0.508 1.346 0.254 0.254 6.200 1.270
Dimensions Inches 0.189 0.150 0.053 0.013 0.047 0.007 0.002 0.228 0.016 0.197 0.157 0.069 0.020 0.053 0.010 0.010 0.244 0.050
8-Lead Plastic Package
Richtek Technology Corporation
Headquarter Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611
Richtek Technology Corporation
Taipei Office (Marketing) 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465 Email: marketing@richtek.com
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DS9603-08 March 2007
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