Multi-Phase Controller Core Power Supply RT9246A multi-phase buck

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Multi-Phase Controller Core Power Supply RT9246A multi-phase buck

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RT9246A
Multi-Phase Controller Core Power Supply
RT9246A multi-phase buck DC/DC controller integrated with control functions VRM. RT9246A controls buck switching stages operating interleaved phase automatically. multiphase architecture provides high output current while maintaining power dissipation power devices stress input output capacitors. high equivalent operating frequency also reduces component dimension output voltage ripple load transient. RT9246A controls both voltage current loops achieve good regulation, response power stage thermal balance. Precise current loop using Inductor sense component builds precise load line strict transient specification also ensures thermal balance different power stages. settings current sense, droop tuning, VCORE initial offset over current protection independent compensation circuit voltage loop. feature greatly facilitates flexibility power supply design tuning. output RT9246A supports 5-bit input, precise initial value smooth VCORE transient jump. monitors VCORE voltage PGOOD over-voltage protection. Soft-start, over-current protection programmable under-voltage lockout also provided assure safety microprocessor power system.
Features
Multi-Phase Power Conversion with Automatic Phase Selection Output with Active Droop Compensation Fast Load Transient Smooth VCORE Transition Jump Power Stage Thermal Balance Inductor Current Sense Hiccup Mode Over-Current Protection Programmable Switching Frequency (50kHz 400kHz Phase), Under-Voltage Lockout Soft-Start High Ripple Frequency Times Channel Number RoHS Compliant 100% Lead (Pb)-Free
Applications
AMD® Athlon64 OpteronProcessors Voltage Regulator Output Voltage, High Current DC-DC Converters Voltage Regulator Modules
Configurations
(TOP VIEW)
VID4 VID3 VID2 VID1 VID0 FBRTN COMP PGOOD VOSS PWM1 PWM2 PWM3 ISP1 ISP2 ISP3 IOUT ICOMMON IMAX
Ordering Information
RT9246A Package Type TSSOP-28 Operating Temperature Range Free with Commercial Standard Green (Halogen Free with Commercial Standard)
TSSOP-28
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. DS9246A-04 March 2007 www.richtek.com
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ATX_12V 10uF 10uF 1000uF 10uF 1000uF 10uF ATX_12V ATX_5V BOOT UGATE PHASE PGND LGATE 3.3nF 1N4148
RT9246A
RT9619
0.3uH
Typical Application Circuit
VID4 PWM1 PWM2 PWM3 BOOT UGATE PHASE LGATE PGND ISP1 ISP2 ISP3 ATX_12V 1N4148 IOUT ICOMMON IMAX VCORE LGATE PGND VCOREFB_H 1N4148 ATX_12V
VID4
VID3
VID3
VCORE 3.3nF 10uF 10uF 1000uF 0.3uH
VID2
VID2
VID1
VID1
VID0
VID0
RT9619
560uF
33pF
FBRTN
22uF
10nF
RT9246A
COMP
ATX_5V
PGOOD
ATX_12V
9.1k
0.1uF
RT9619
BOOT UGATE PHASE
10uF
10uF
1000uF 0.3uH 3.3nF
VOSS
DS9246A-04 March 2007
RT9246A
Functional Description
VID4 (Pin VID3 (Pin VID2 (Pin VID1 (Pin VID0 (Pin voltage identification inputs These pins internally pulled 2.2V left open. (Pin Input Connection FBRTN (Pin VCORE differential sense return. (Pin Inverting input internal error amplifier. COMP (Pin Output error amplifier input comparator. PGOOD (Pin Power good open-drain output. (Pin Programmable power UVLO detection converter enable input. (Pin Connect this with capacitor soft-start time interval smooth VCORE transient Jump. (Pin Switching frequency setting. Connect this with resistor frequency. VOSS (Pin VCORE initial value offset. Connect this with resistor offset value. IMAX (Pin Over-Current protection set. ICOMMON (Pin Common negative input current sense amplifiers three channels. IOUT (Pin Output current indication pin. current through IOUT proportional output current. (Pin
Oscillator Ferquency
Current sense output active droop adjust. Connect resistor from this load droop. (Pin ground. ISP1 (Pin 23), ISP2 (Pin 22), ISP3 (Pin Current sense positive input pins individual converter channel current sensing. PWM1 (Pin 27), PWM2 (Pin 26), PWM3 (Pin outputs each driven channel. Connect these pins input MOSFET driver. systems which channels, connect PWM3 high. (Pin power supply. Connect this supply.
Oscillator Ferquency (kHz)
DS9246A-04 March 2007
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Function Block Diagram
VID0 VID1 VID2 VID3 VID4 Setting Power Reset
PWMCP
Oscillator Sawtooth
FBRTN Trip Point
Droop
Trip Point
Offset Currrent Source/Sink
VOSS
Current Correction
Control
COMP
IOUT
ERROR
SUM/M
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IMAX PGOOD
RT9246A
Logic Driver
PWM1
Logic Driver
PWM2
PWMCP
Logic Driver PWMCP
PWM3
ICOMMON ISP1 ISP2 ISP3
DS9246A-04 March 2007
RT9246A
Table Output Voltage Program
VID4 VID3 VID2 VID1 VID0 Nominal Output Voltage DACOUT 1.550 1.525 1.500 1.475 1.450 1.425 1.400 1.375 1.350 1.325 1.200 1.275 1.250 1.225 1.200 1.175 1.150 1.125 1.100 1.075 1.050 1.025 1.000 0.975 0.950 0.925 0.900 0.875 0.850 0.825 0.800 Shutdown
Note: Connected Open
DS9246A-04 March 2007
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RT9246A
Absolute Maximum Ratings
(Note GND-0.3V VCC+0.3V 100°C/W 150°C 260°C -65°C 150°C 200V Supply Voltage, -Input, Output Voltage -Power Dissipation, 25°C TSSOP-28 -Package Thermal Resistance (Note TSSOP-28, -Junction Temperature -Lead Temperature (Soldering, sec.) -Storage Temperature Range -ESD Susceptibility (Note (Human Body Mode) (Machine Mode)
Recommended Operating Conditions
(Note
Supply Voltage, Ambient Temperature Range 70°C Junction Temperature Range 125°C
Electrical Characteristics
(VCC 25°C, unless otherwise specified)
Parameter Supply Current Nominal Supply Current Power-On Reset Threshold Hysteresis VDVD Threshold Oscillator Free Running Frequency Frequency Adjustable Range Ramp Amplitude Ramp Valley Maximum On-Time Each Channel Voltage Reference DACOUT Voltage Accuracy (VID0-VID4) Input (VID0-VID4) Input High
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Symbol
Test Conditions
Units
VCCRTH VCCHYS
1,2,3 Open
-1.9
-4.5 -1.1 -230
Rising Enable
-170
Input High Input
VDVDTH VDVDHYS fOSC fOSC_ADJ VOSC
VDAC VDAC
VDAC VILDAC VIHDAC
-1.2
continued
DS9246A-04 March 2007
RT9246A
Parameter (VID0-VID4) Pull-up Voltage (VID0-VID4) Pull-up Resistance VOSS Voltage Error Amplifier Gain Gain-Bandwidth Product Slew Rate Current Sense Amplifier ICOMMON Full Scale Source Current ICOMMON Current Protection IMAX Voltage Over-Voltage Trip (VFB- VDAC) Power Good Output Voltage VPGOODL IPGOOD -0.2 VIMAX RIMAX RADJ 0.84 0.94 1.05 CCOMP 10pF VVOSS RVOSS 100k Symbol Test Conditions Units
Note Stresses listed above "Absolute Maximum Ratings" cause permanent damage device. These stress ratings. Functional operation device these other conditions beyond those indicated operational sections specifications implied. Exposure absolute maximum rating conditions extended periods remain possibility affect device reliability. Note Devices sensitive. Handling precaution recommended. Note device guaranteed function outside operating conditions. Note measured natural convection 25°C effective thermal conductivity test board JEDEC 51-3 thermal measurement standard.
DS9246A-04 March 2007
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RT9246A
Typical Operating Characteristics
Duty Ratio VCOMP
Power
IOUT
Duty Ratio
(5V/Div) (2V/Div)
(1V/Div)
VOUT
PGOOD
(5V/Div)
Time (25ms/Div)
VCOMP
Power
IOUT
Start
(5V/Div) (2V/Div)
(5V/Div)
(2V/Div) (1V/Div)
VOUT
(1V/Div) (1V/Div)
COMP
PGOOD
(5V/Div)
CORE
Time (25ms/Div)
Time (10ms/Div)
Jump
Unit Gain
(2V/Div)
(100mV/Div)
CORE
(2V/Div)
(500mV/Div)
(2V/Div)
Time (5ms/Div)
Time (5ms/Div)
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DS9246A-04 March 2007
RT9246A
Applications Information
RT9246A multi-phase DC/DC controller specifically designed deliver high quality power next generation CPU. Phase currents sensed innovative timesharing current sensing technique channel current balance, droop tuning, over current protection. Using common amplifier current sensing eliminates offset errors linearity variation between GMs. submilli-ohm-grade inductors widely used modern mother boards, slight mismatch amplifiers offset linearity results considerable current shift between phases. time-sharing current sensing technique extremely important guarantee phase current balance mass production. Converter Initialization, Phase Selection, Power Good Function RT9246A initiates only after pins ready: power reset (POR) higher than make sure RT9246A powered voltage normal work. rising threshold voltage 4.2V typically. POR, RT9246A checks PWM3 status determine phase number operation. Pull high PWM3 two-phase operation. unused current sense should connected left floating. make sure that ATX12V ready companion MOSFET drivers(RT960X series) work normally. Connect voltage divider from ATX12V shown Typical Application Circuit. Make sure that voltage below threshold voltage before drivers ready above threshold voltage minimum ATX12V during normal operation. either ready, RT9246A keeps outputs high impedance companion drivers turn both upper lower MOSFETs. After ready, RT9246A initiates soft start cycle shown Figure time-variant internal current source charges capacitor connected pin. voltage ramps piecewise linearly locks VID_DAC output with specified voltage drop. Consequently, VCORE built according VID_DAC output. PGOOD output tripped high impedance when VCORE reaches VID_DAC output with 1~2ms delay. capacitor about 47nF recommend typical application.
ready VCORE PGOOD
Jump 1~2ms 1~2ms 1~2ms
Figure Timming Diagram During Soft Start Interval Voltage Control VCORE voltage Kelvin sensed FBRTN pins precisely regulated VID_DAC output internal high gain Error Amplifier (EA). sensed signal also used power good over voltage function. typical trip point 400mV above VID_DAC output. RT9246A pulls outputs latches upon trip prevent from damaging. only restart resetting either pin. pins internally pulled high internal 2.2V with resistors easily interfaced with outputs. change VID_DAC output Jump also smoothed capacitor connected pin. Consequently, VCORE shifts position smoothly. Current Sensing RT9246A adopts innovative time-sharing current sensing technique sense phase currents phase current balance (phase thermal balance) load line regulation shown Figure Current sensing amplifier samples holds voltages across current sensing capacitor turns switching cycle. According Basic Circuit Theory, then Consequently, sensing current proportional inductor current expressed RCOMM
DS9246A-04 March 2007
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RT9246A
VCORE
RCOMM
Figure
sensed current used current balance droop tuning described followed. Since phases share common offset linearity variation effect eliminated practical applications. sub-milli-ohmgrade inductors widely used modern mother boards, slight mismatch amplifiers offset linearity results considerable current shift between phases. timesharing current sensing technical extremely important guarantee phase current balance mass production. Phase Current Balance sampled held phase current summed averaged averaged current Each phase current then compared with averaged current. difference between injected corresponding comparator. phase current smaller than averaged current RT9246A increases duty cycle corresponding phase increase phase current accordingly, vice versa.
Over Current Protection RT9246A uses external resistor RIMAX connected IMAX generate reference current IIMAX over current protection: IIMAX= VIMAX RIMAX
where VIMAX 1.0V typical. comparator compares each sensed phase current with this reference current shown Figure Equivalently, maximum phase current calculated ILX(MAX)= VIMAX RCOMM RIMAX
Comparator
IIMAX
Figure Over Current Comparator RT9246A uses hiccup mode eliminate nuisance detection reduce output current when output shorted ground shown Figure
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DS9246A-04 March 2007
RT9246A
Over Current Protection
(5V/Div)
where phase number operation. averaged current also injected into resistor RIOUT connected IOUT monitoring load current. Voltage IOUT VIOUT proportional load current calculated VIOUT RIOUT ICORE RADJ RCOMM
Error Amp. VADJ
(10A/Div)
CORE
(2V/Div)
VCORE
(500mV/Div)
VCORE
RFB1
IVOSS
Time (5ms/Div)
Figure Over Current Protection soft start interval
RADJ
Over Current Protection
Figure Load Line Offset Function Output Voltage Offset Function
(5A/Div)
RT9246A provides programmable initial offset function. External resistor RVOSS voltage source VOSS generate offset current IVOSS
CORE
(1V/Div)
where VVOSS typical. quarter IVOSS flows through RFB1 shown Figure Error amplifier would hold inverting equal VDAC VADJ. constant offset voltage consequently added VDAC VADJ
Time (2.5ms/Div)
VOSS VOSS
VCORE VDAC VADJ
RFB1 RVOSS
Figure Over Current Protection steady state Current Ratio Setting Droop Load Line Setting RT9246A injects averaged phase current into resistor RADJ connected generate loadcurrent-dependent voltage VADJ droop setting:
VADJ RADJ
VADJ then subtracted form VID_DAC output real reference voltage non-inverting input error amplifier shown Figure Consequently, load line slope calculated Load Line VCORE RADJ ICORE RCOMM
Current ratio adjustment possible described below. important achieving thermal balance practical application where thermal conditions between phases identical. Figure shows application circuit current ratio requirement. According Basic Circuit Theory,
(RSX RPX) then RSX+RPX
DS9246A-04 March 2007
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RT9246A
With other phase kept unchanged, this phase would share (RPX+RSX)/RPX times current than other phases. Figure show different current ratio setting power stage when Phase programmed times current than other phases. Figure compare above current ratio setting results.
Phase Current Balance
Phase Current
VCORE
CORE
Figure
Current Ratio Function
Figure
Figure Phase Setting current ratio function
Figure Dead Zone Elimination RT9246A samples holds inductor valley current time-sharing sourcing current RCOMM. light load condition when averaged inductor current smaller than half peak-to-peak inductor ripple current, voltage across sensing capacitor negative valley. needs negative sense voltage. However, RT9246A CANNOT provide negative consequently cannot sense negative valley inductor current. This results dead zone load line performance shown Figure Therefore technique shown Figure required eliminate dead zone load line light load condition.
Figure Phase Setting current ratio function
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DS9246A-04 March 2007
RT9246A
Load Line without dead zone light loads
1.31 1.29
RCOMM 330, RADJ 160, VOUT 1.300V
1.3V RCSN
Dead Zone Compensation RCSN open
CORE
1.28 1.27 1.26 1.25 1.24 1.23
RCSN 85.8k Choose RCSN Figure shows that dead zone load line light load eliminated applying this technique. Error Amplifier Characteristic fast response converter meet stringent output current transient response, RT9246A provides large slew rate capability high gain-bandwidth performance.
RCSN Dead Zone Compensation
Figure
Falling Slew Rate
VOUT
500mV/Div) (2V/Div)
RCOMM RCSN
VCOMP
Figure13. Application circuit Referring Figure expressed VOUT ILX_V ILX_V RCSN RCSN RCOMM
Time (250ns/Div)
Figure Rising Transient with 10pF Loading; Slew Rate=8V/us
Rising Slew Rate
where ILX_V valley inductor current. make sure RT9246A could sense valley current, right hand side Equation should always positive: VOUT ILX_V ILX_V RCSN RCSN RCOMM
(500mV/Div)
Since RCSN RCOMM practical application, Equation could simplified
VOUT ILX_V RCSN RCOMM
VCOMP
(2V/Div)
example, assuming negative inductor valley current load, then
Time (250ns/Div)
Figure Falling Transient with 10pF Loading; Slew Rate=8V/us
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DS9246A-04 March 2007
RT9246A
4.7k 4.7k
VREF
Figure Gain-Bandwidth Measurement signal divided signal Design Procedure Suggestion a.Output filter pole zero (Inductor, output capacitor value ESR). b.Error amplifier compensation sawtooth wave amplitude (compensation network). Current Loop Setting a.GM amplifier current (current sense component DCR, ISPX ICOMMON external resistor value). b.Over-current protection trip point (RIMAX resistor). Load Line Setting a.Droop amplitude (ADJ resistor). b.No load offset (RCSN) c.DAC offset voltage setting (VOSS compensation network resistor RB1) Power Sequence external resistor capacitor. Layout a.Sense current sense amplifier input. b.Refer layout guide other items. Voltage Loop Setting Design Example Given: Apply four phase converter VCORE 1.5V ILOAD(MAX) 100A VDROOP 100mV full load Load Line) trip point each channel (S/H) Figure Type compensation network
4.7k 68pF
inductor 25°C 1.5H COUT 8000F with equivalent ESR. Compensation Setting Modulator Gain, Pole Zero: From following formula: Modulator Gain =VIN/VRAMP =12/1.9 (i.e 16dB) where VRAMP ramp amplitude saw-tooth wave Filter Pole 1.45kHz Zero =3.98kHz Compensation Network: Select 4.7k, 15k, 12nF, 68pF Type compensation scheme shown Figure calculation, 0.88kHz, 322kHz Middle Band Gain 3.19 (i.e 10.07dB).
12nF
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DS9246A-04 March 2007
RT9246A
Layout Guide
Place high-power switching components first, separate them from sensitive nodes. Most critical path: current sense circuit most sensitive part converter. current sense resistors tied ISP1,2,3 ICOMMON should located more than inch from away from noise switching nodes. trace sense nodes should parallel short possible. filter choke should place close connect directly each output choke, differencial pair, other phase pair. Less possible. Switching ripple current path: Input capacitor high side MOSFET. side MOSFET output capacitor. return path input output capacitor. Separate power signal GND. switching nodes (the connection node high/low side MOSFET inductor) most noisy points.Keep them away from sensitive small-signal node. Reduce parasitic minimum length, enough copper thickness avoiding via. MOSFET driver should closed MOSFET.
VOUT
COUT
Figure Power Stage Ripple Current Path
DS9246A-04 March 2007 www.richtek.com
RT9246A
Outline Dimension
Symbol
Dimensions Millimeters 0.850 0.050 0.800 0.178 9.601 0.650 6.300 4.293 0.450 6.500 4.496 0.762 1.200 0.152 1.050 0.305 9.804
Dimensions Inches 0.033 0.002 0.031 0.007 0.378 0.026 0.248 0.169 0.018 0.256 0.177 0.030 0.047 0.006 0.041 0.012 0.386
28-Lead TSSOP 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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DS9246A-04 March 2007

Multi-Phase Controller Core Power Supply RT9246A multi-phase buck

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