Dual Channel Synchronous-Rectified Buck MOSFET Driver RT9602 dual

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Dual Channel Synchronous-Rectified Buck MOSFET Driver RT9602 dual

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RT9602
Dual Channel Synchronous-Rectified Buck MOSFET Driver
RT9602 dual power channel MOSFET driver specifically designed drive four power N-Channel MOSFETs synchronous-rectified buck converter topology. These drivers combined with RT9237/A RT9241A/B series Multi-Phase Buck controllers provide complete core voltage regulator solution advanced microprocessors. RT9602 provide flexible gate driving both high side side drivers. This gives more flexibility MOSFET selection. output drivers RT9602 have capability drive 3000pF load with 40nS propagation delay 80nS transition time. This device implements bootstrapping upper gates with only single external capacitor required each power channel. This reduces implementation complexity allows higher performance, cost effective, N-Channel MOSFETs. Adaptive shoot-through protect-ion integrated prevent both MOSFETs from conducting simultaneously. RT9602 detect high side MOSFET drain-to-source electrical short power pull power side cause power supply into over current shutdown prevent damage CPU.
Features
Drives Four N-Channel MOSFETs Adaptive Shoot-Through Protection Internal Bootstrap Devices Small 14-Lead SOIC Package Gate-Drive Voltages Optimal Efficiency Tri-State Input Bridge Shutdown Supply Under-Voltage Protection Power Over-Voltage Protection
Applications
Core Voltage Supplies Intel Pentium® AMD® AthlonMicroprocessors High Frequency Profile DC-DC Converters High Current Voltage DC-DC Converters
Configurations
(TOP VIEW)
PWM1 PWM2 LGATE1 PVCC PGND LGATE2 PHASE1 UGATE1 BOOT1 BOOT2 UGATE2 PHASE2
SOP-14
Ordering Information
RT9602 Package Type SOP-14 Operating Temperature Range Commercial Standard Free with Commercial Standard
DS9602-03 March 2004
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RT9602
Optional 1.2uH 1000uF UGATE1
PHB83N03LT
BOOT1 PVCC
Typical Application Circuit
PGOOD x1500uF
PHB95N03LT
VID4
VID3
VID4 VID3 PGOOD RT9602 LGATE1
PHASE1 PWM1
VID2 1000uF ISP2 ISN2 x1500uF
PHB95N03LT PHB83N03LT
2.4K
VID1
VID0
PWM2 UGATE2 PHASE2 LGATE2 PGND
66pF
VID2 PWM1 ISP1 VID1 VID0 ISN1 COMP VSEN
2.4K
BOOT2 Optional
0.1uF
PWM2 RT9241A/B
VCORE
DS9602-03 March 2004
RT9602
Functional Description
Name PWM1 PWM2 LGATE1 PVCC PGND LGATE2 PHASE2 UGATE2 BOOT2 BOOT1 UGATE1 PHASE1 Channel Input Channel Input Ground Lower Gate Drive Channel Upper Lower Gate Driver Power Rail Lower Gate Driver Ground Lower Gate Drive Channel Connect this phase point channel Phase point connection point high side MOSFET source side MOSFET drain Upper Gate Drive Channel Floating Bootstrap Supply Channel Floating Bootstrap Supply Channel Upper Gate Drive Channel Connect this phase point channel Phase point connection point high side MOSFET source side MOSFET drain Control Logic Power Supply Function
DS9602-03 March 2004
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RT9602
Function Block Diagram
PVCC
Internal
BOOT1 Shoot-Through Protection UGATE1 PHASE1 Power-On
PWM1 Shoot-Through Protection PGND PVCC Shoot-Through Protection PWM2 Power-On PVCC Shoot-Through Protection
PVCC LGATE1
Internal
Control Logic
PGND BOOT2 UGATE2 PHASE2
LGATE2
PGND
Absolute Maximum Ratings
Supply Voltage (VCC) Supply Voltage (PVCC) 0.3V BOOT Voltage (VBOOT -VPHASE) Input Voltage (VPWM) 0.3V UGATE 0.3V VBOOT 0.3V PHASE LGATE 0.3V 0.3V PVCC Package Thermal Resistance SOP-14, 127.67° Ambient Temperature Junction Temperature 125° Storage Temperature Range -40° 150° Lead Temperature (Soldering, sec.) 260°C Level (Note) 200V
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DS9602-03 March 2004
RT9602
Electrical Characteristics
Parameter Supply Current Bias Supply Current Power Supply Current Power-On Reset Rising Threshold Hysteresis Input Maximum Input Current Floating Voltage Rising Threshold Falling Threshold UGATE Rise Time LGATE Rise Time UGATE Fall Time LGATE Fall Time UGATE Turn-Off Propagation Delay LGATE Turn-Off Propagation Delay Shutdown Window Output Upper Drive Source Upper Drive Sink Lower Drive Source Lower Drive Sink RUGATE VVCC 12V, VPVCC RUGATE VVCC 12V, VPVCC RLGATE VVCC 12V, VPVCC RLGATE VVCC VPVCC -1.75 VPVCC VVCC 12V, load VPVCC VVCC 12V, load VPVCC VVCC 12V, load VPVCC VVCC 12V, load VVCC VPVCC 12V, load VVCC VPVCC 12V, load VPWM -1.26 1.26 -150 -3.7 1.35 10.7 IVCC IPVCC fPWM 250kHz, PVCC 12V, CBOOT 0.1µF, RPHASE fPWM 250kHz, VPVCC 12V, CBOOT 0.1µF, RPHASE -5.5 Symbol Test Conditions Units
Note: Devices sensitive, especially PHASE LGATE pins. Handling precaution recommended. human body model 100pF capacitor discharged through 1.5kW resistor into each pin.
DS9602-03 March 2004
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RT9602
Application Information
RT9602 power protection function which held UGATE LGATE before cross rising threshold voltage. After initialization, signal takes control. rising signal first forces LGATE signal turns then UGATE signal allowed high just after non-overlapping time avoid shootthrough current. falling signal first forces UGATE low. When UGATE PHASE signal reach predetermined level, LGATE signal allowed turn high. non-overlapping function also presented between UGATE LGATE signal transient. signal recognized high above rising threshold below falling threshold. signal level this window considered tri-state, which causes turn-off both high side low-side MOSFET. When input floating (not connected), internal divider will pull 1.9V give controller recognizable level. maximum sink/source capability internal reference 60µA. PVCC provides flexibility both high side side MOSFET gate drive voltages. example, applied PVCC, then high side MOSFET gate drive 1.5V (approximately, internal diode plus series resistance voltage drop). side gate drive voltage exactly RT9602 implements power over-voltage protection function. PHASE voltage exceeds 1.5V power LGATE would turn pull PHASE until PHASE voltage goes below 1.5V. Such function protect from damage some short condition happened before power which sometimes encountered manufacturing line. Driving power MOSFETs input impedance power MOSFET extremely high. When 5V), gate draws current only nanoamperes. Thus once gate been driven "ON"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
Igd1 Igs1 Igd2
Cgs1
Cgd2
Igs2
Cgs2
+12V
+12V
Figure1. gate driver must supply Figure current required move gate 12V.The operation consists charging Cgs. Cgs1 Cgs2 capacitances from gate source high side side power MOSFETs, respectively. general data sheets, referred "Ciss" 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
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DS9602-03 March 2004
RT9602
lgs1 dVg1 dVg2
from equation.
lgs2
0.326
(A)(7)
lgs2
According design RT9602, 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
0.4(A)(8)
total current required from gate driving source
Igs1 Igd1 (1.428 0.326) 1.745(A) (0.88 1.28(A)
(10)
lgd1=
Cgd1
similar calculation, also sink current required from turned MOSFET. Layout Consider Figure shows schematic circuit two-phase synchronous-buck converter implement RT9602. converter operates input rang from 12V.
1.2uH 1000uF
PHB83N03LT
Before side MOSFET turned Cgd2 have been charged Thus, Cgd2 reverses polarity charged 12V, required current
lgd2
PVCC
BOOT1 UGATE1 PHASE1
helpful calculate these currents typical case. Assume synchronous rectified BUCK converter, input voltage 12V, 12V. high side MOSFET PHB83N03LT whose Ciss 1660pF, Crss 380pF,and 14nS. side MOSFET PHB95N03LT whose Ciss 2200pF, Crss 500pF, 30nS, from equation obtain
1500uF
PHB95N03LT
PWM1
PWM1
RT9602 LGATE1 PWM2 1000uF
PHB83N03LT
PWM2
UGATE2 PHASE2 LGATE2 PGND
1500uF
BOOT2
PHB95N03LT
lgs1
1.428
CORE
Figure Two- Phase Synchronous-Buck Converter Circuit
lgs2
0.88
DS9602-03 March 2004
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RT9602
When layout board, should very careful. power-circuit section most critical one. configured properly, will generate large amount EMI. junction should very close. connection from drain positive sides connection from source negative sides should short possible. Next, trace from Ugate1, Ugate2, Lgate1, Lgate2 should also short decrease noise driver output signals. Phase1 phase2 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 (Cb1, Cb2) should always placed close pins possible. Select Bootstrap Capacitor Figure shows part bootstrap circuit RT9602. (the voltage difference between BOOT1 PHASE1 RT9602) provides voltage gate high side power MOSFET. This supply needs ensured that MOSFET driven. this, capacitance selected properly. determined following constraints.
PVCC BOOT1
PWM2 PWM1 RT9602 0.01uF
practice, value capacitor will lead overcharging that could damage Therefore minimize risk overcharging reducing ripple VCB, bootstrap capacitor should smaller than 0.1µF, larger better. general design, using provide better performance. least low-ESR capacitor should used provide good local de-coupling. 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. UGATE LGATE load capacitors, respectively. bootstrap capacitor value 0.01µF.
+12V +12V 0.01uF
UGATE1 +12V PHASE1 LGATE1
2N7000
2N7000
UGATE1 PHASE1 PVCC LGATE1 PGND
UGATE2
2N7000
PGND PHASE2 LGATE2
2N7000
Figure RT9602 Power Dissipation Test Circuit Figure Part Bootstrap Circuit RT9602 Figure shows power dissipation RT9602 function frequency load capacitance. value same frequency varied from 100kHz 600kHz. PVCC connected together. Figure 6.shows same characterization PVCC tied instead 12V.
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DS9602-03 March 2004
RT9602
Power Dissipation Frequency
CU=CL
=5nF
CU=CL=4nF CU=CL=3nF CU=CL=2nF CU=CL=1nF
method improve thermal transfer increase board copper area around RT9602, first. Then, adding ground under transfer heat peripheral board. Power Over-Voltage Protection Function RT9602 provides protect function which avoid some short condition happened before power following discussion about power over-voltage protection function RT9602 based experiments high side MOSFET directly shorted 12V. test circuit shown typical application circuit (with RT9241A/B dual-channel synchronous-rectified buck controller) phase signals measured phase RT9602. LGATE signal measured gate terminal MOSEFET.
Power (mW)
PVcc=Vcc=12V
Frequency (kHz)
Figure Power Dissipation Frequency (RT9602)
Power Dissipation Frequency
CU=CL =5nF CU=CL=1nF CU=CL=4nF CU=CL=2nF
VVcc PPEASE
Power(mW)
lLGATE
CU=CL=3nF
hrountCurrent
Through Time (50ms)
RT9809-20CV
Frequency(kHz)
Figure High Side Direct Short
Figure Power Dissipatin Frequency, PVCC operating junction temperature calculated from power dissipation curves (Figure Figure Assume RT9602' PVCC VCC=12V, operating frequency 200kHz, CU=CL=1.5nF which emulate input capacitances high side side power MOSFETs. From Figure power dissipation 500mW. RT9602, package thermal resistance 127.67C/ operating junction temperature calculated 127.67° 500mW+ 25°C 88.84°C where ambient temperature. (11)
Time (50ms)
VVcc
PPEAS
lLGATE
CORE>
Figure High Side Direct Short
DS9602-03 March 2004
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RT9602
VVcc
PPEASE
lLGATE
lPWM1
Time (25ms)
Figure High Side Direct Short Referring Figure when exceeds 1.5V, RT9602 turns LGATE clamp Phase through side MOSFET. During turn-on side MOSFET, current limited although maximum current listed case 15A. After shuts down, falls slowly. Please note that trigger point RT9602 1.5V VCC, clamped value phase about 2.4V. Next, reference Figure obvious that since Phase voltage increases during power-on, VCORE increases correspondingly, gradually decreased LGATE decrease. Figure during turn-on side MOSFET, much less than 12V, thus RT9241A/B keeps signal high impedance state.
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DS9602-03 March 2004
RT9602
Outline Dimension
Symbol
Dimensions Millimeters 8.534 3.810 1.346 0.330 1.194 0.178 0.102 5.791 0.406 8.738 3.988 1.753 0.508 1.346 0.254 0.254 6.198 1.270
Dimensions Inches 0.336 0.150 0.053 0.013 0.047 0.007 0.004 0.228 0.016 0.344 0.157 0.069 0.020 0.053 0.010 0.010 0.244 0.050
14-Lead Plastic Package
RICHTEK TECHNOLOGY CORP.
Headquarter Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611
RICHTEK TECHNOLOGY CORP.
Taipei Office (Marketing) 8F-1, 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465 Email: marketing@richtek.com
DS9602-03 March 2004
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Dual Channel Synchronous-Rectified Buck MOSFET Driver RT9602 dual

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