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, NChannel MOSFETs. Adaptive shoot-through protection integrated prevent both MOSFETs from conducting simultaneously. RT9602 detect high side MOSFET drain-tosource 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 AthlonMicroprocessors High Frequency Profile DC-DC Converters High Current Voltage DC-DC Converters
Configurations
Part Number RT9602CS (Plastic SOP-14)
PWM1 PWM2 LGATE1 PVCC PGND LGATE2
Configurations
VIEW
PHASE1 UGATE1 BOOT1 BOOT2 UGATE2 PHASE2
Ordering Information
RT9602 Package Type SOP-14 Operating Temperature Range Commercial Standard
DS9602-02 November 2002
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RT9602
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
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DS9602-02 November 2002
RT9602
Function Block Diagram
Internal PWM1 Shoot-through Protection er-on PVCC
BOOT1 UGATE1 PHASE1 PVCC LGATE1 PGND PVCC Shoot-through Protection er-on PGND BOOT2 UGATE2 PHASE2 PVCC LGATE2
Shoot-through Protection
Control Logic
Internal PWM2 Shoot-through Protection
PGND
DS9602-02 November 2002
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RT9602
Absolute Maximum Ratings
Supply Voltage (VCC) Supply Voltage (PVCC) BOOT Voltage (VBOOT-VPHASE) Input Voltage (VPWM) UGATE LGATE Package Thermal Resistance SOP-14, Ambient Temperature Junction Temperature Storage Temperature Range Lead Temperature (Soldering, sec.) Level (Note) 0.3V 0.3V VPHASE 0.3V VBOOT 0.3V 0.3V VPVCC 0.3V 127.67°C 70°C 125°C -40°C 150°C 260°C 200V
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 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, VPVCC 12V, CBOOT 0.1µF, RPHASE fPWM 250kHz, VPVCC 12V, CBOOT 0.1µF, RPHASE -5.5 Symbol Test Conditions Units
continued
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DS9602-02 November 2002
RT9602
Parameter 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 Symbol Test Conditions Units
Note: Devices sensitive, especially PHASE LGATE pins. Handling precaution recommended. human
body model 100pF capacitor discharged through 1.5K resistor into each pin.
Operation Descriptions
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 nonoverlapping time avoid shoot-through 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
DS9602-02 November 2002 www.richtek.com
PHASE until PHASE voltage goes below 1.5V. Such function protect from damage some short condition happened before power which sometimes encountered manufacturing line.
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RT9602
optional
1.2µH 1000µF PHB83N03LT PHB95N03LT PHASE1 UGATE1 PVCC PGOOD VID4 PGOOD PWM1 ISP1 ISN1 VSEN PHB83N03LT 1000µF VID3 VID2 VID1 VID0 COMP BOOT1
VID4
Typical Application Circuit
VID3
VID2
VID1
PWM1
2.4K
VID0
RT9602
LGATE PWM2 UGATE2
66pF
2.4K PWM2 ISN2 ISP2 PHASE2
PGND LGATE BOOT2
0.1µF
RT9241A/B
optional
PHB95N03LT
DS9602-02 November 2002
VCORE
RT9602
Application Information
Driving power MOSFETs input impedance power MOSFET extremely high. When 5V), gate draws current only nanoamperes. 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.
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
Igs1 Cgs1
Cgd1 Igd1 Igs1
Cgs1
Igs2
Cgd2
dVg2
Igd2 Igs2
Cgs2
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
Before side MOSFET turned Cgd2 have been charged Thus, Cgd2 reverses polarity charged 12V, required current
Igd2
Figure gate driver must supply
DS9602-02 November 2002
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RT9602
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
1660 1.428(A)
2200 0.88(A)
1000uF
BOOT1
PVCC
PHB83N03LT
1500uF
UGATE1 PHASE1
PWM1
PWM1
PHB95N03LT
RT9602
LGATE1 PWM2 UGATE2
PWM2
Igs1
1000uF
PHASE2 PGND
1500uF
PHB83N03LT
LGATE2 BOOT2
from equation.
PHB95N03LT
Igd1
0.326(A)
0.4(A)
VCORE
Figure Two- Phase Synchronous-Buck Converter Circuit
total current required from gate driving source
Igs1 (1.428 0.326 1.745(A)
Igd2 (0.88 0.4) 1.28(A)
(10)
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.
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.
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DS9602-02 November 2002
RT9602
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
+12V
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.
UGATE1
+12V
0.01
+12V UGATE1 PHASE1
2N7000
PHASE1
PVCC
LGATE1 PWM1 2N7000
LGATE1
0.01 PWM2 RT9602 UGATE2 PGND PHASE2 LGATE2 2N7000 2N7000
PGND
Figure Part Bootstrap Circuit RT9602
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.
Figure RT9602 Power Dissipation Test Circuit
Figure shows power dissipation RT9602 function frequency load capacitance. value same frequency varied from 100kHz 600kHz. PVCC connected together. Figure shows same characterization PVCC tied instead 12V.
DS9602-02 November 2002
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RT9602
Power Dissipation Frequency
CU=CL =5nF
POWER (mW)
CL=4nF CL=3nF CL=2nF PVCC
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 overvoltage 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.
FREQUENCY (kHz)
Figure Power Dissipation Frequency (RT9602)
Power Dissipation Frequency
CU=CL =5nF
CL=4nF CL=2nF
POWER(mW)
CL=3nF
PHASE
PVCC
LGATE Current Through 10A/Div
FREQUENCY(kHz)
Figure Power Dissipation Frequency, PVCC
operating junction temperature calculated from power dissipation curves (Figure Figure Assume RT9602's 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 127.67°C/W, operating junction temperature calculated 127.67°C/W 500mW+ 25°C 88.84°C (11)
Time (50mS) Figure High Side Direct Short
PHASE
LGATE VCORE
where 25°C ambient temperature.
Time (50mS) Figure High Side Direct Short
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DS9602-02 November 2002
RT9602
PHASE
LGATE PWM1
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.
DS9602-02 November 2002
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RT9602
Package Information
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
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DS9602-02 November 2002
RT9602
DS9602-02 November 2002
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RT9602
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
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DS9602-02 November 2002

Dual Channel Synchronous-Rectified Buck MOSFET Driver RT9602 dual

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