SC1172/3 DESCRIPTION SC1172/3 combines synchronous voltage m
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PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER WITH DROPOUT REGULATOR CONTROLLER
SC1172/3
DESCRIPTION
SC1172/3 combines synchronous voltage mode controller with low-dropout linear regulator providing most circuitry necessary implement DC/DC converters powering advanced microprocessors such Pentium (Klamath) Deschutes. SC1172/3 switching section features integrated converter, pulse pulse current limiting, integrated power good signaling, logic compatible shutdown. SC1172/3 switching section operates fixed frequency 200kHz, providing optimum compromise between size, efficiency cost intended application areas. integrated converter provides programmability output voltage from 2.0V 3.5V 100mV increments 1.30V 2.05V 50mV increments with external components. SC1172/3 linear section high performance positive voltage regulator design either supply 1.5V (SC1172) adjustable output (SC1173). output linear regulator provide more with appropriate external MOSFET.
FEATURES Synchronous design, enables heatsink solution efficiency (switching section) output programmability chip power good function Designed Intel Pentium® VRM8.1
ments 1.5V Adj. linear section
APPLICATIONS Pentium® Deschutes microprocessor supplies Flexible motherboards 1.3V 3.5V microprocessor supplies Programmable dual power supplies ORDERING INFORMATION
Part Number
Package
Linear Voltage
Temp. Range (TJ)
SC1172CSW SC1173CSW
SO-24 SO-24
1.5V Adj.
125°C 125°C
Note: suffix `TR' tape reel.
CONFIGURATION
BLOCK DIAGRAM
BSTH 1.25 70mV VID4 VID3 VID2 VID1 VID0 SHUTDOWN LOGIC CURRENT LIMIT LEVEL SHIFT HIGH SIDE MOSFET DRIVE OSCILLATOR PGNDH
View
AGND LDOS PWRGOOD CSCS+ PGNDH PGNDL GATE LDOV VID0 VID1 VID2 VID3 VID4 VOSENSE BSTH BSTL
VOSENSE OPEN COLLECTORS PWRGOOD
SHOOTTHRU CONTROL ERROR SYNCHRONOUS MOSFET DRIVER BSTL
SOIC)
PGNDL AGND 1.25V CONTROLLER
LDOV
GATE
LDOS
Pentium registered trademark Intel Corporation
1999 SEMTECH CORP.
MITCHELL ROAD NEWBURY PARK 91320
PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER WITH DROPOUT REGULATOR CONTROLLER
SC1172/3
ABSOLUTE MAXIMUM RATINGS
Parameter PGND Operating Temperature Range Junction Temperature Range Storage Temperature Range Lead Temperature (Soldering) seconds Thermal Impedance Junction Ambient Thermal Impedance Junction Case TSTG Symbol Maximum -0.3 -0.3 +125 +150 Units °C/W °C/W
ELECTRICAL CHARACTERISTICS
Unless specified: 4.75V 5.25V; PGND VOSENSE (CSp-CSm) 60mV; LDOV 11.4V 12.6V; 25oC
PARAMETER Switching Section Output Voltage Supply Voltage Supply Current Load Regulation Line Regulation Minimum operating voltage Current Limit Voltage Oscillator Frequency Oscillator Duty Cycle Sink/Source Current Sink/Source Current Output Voltage Tempco Gain (AOL) threshold voltage source current Power good threshold voltage Dead time Linear Section Quiescent current Output Voltage (SC1172) Reference Voltage (SC1173) Feedback Bias Current (SC1173) Gain (AOL) Load Regulation Line Regulation Output Impedance Notes: Output Voltage table application circuit 1999 SEMTECH CORP.
CONDITIONS 0.8A
UNITS
Note ppm/
BSTH-DH 4.5V, DH-PGNDH BSTL-DL 4.5V, DL-PGNDL
VOSENSE VOVP 3.0V
LDOV
LDOS GATE
1.485 1.500 1.515 1.252 1.265 1.278
MITCHELL ROAD NEWBURY PARK 91320
PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER WITH DROPOUT REGULATOR CONTROLLER
SC1172/3
DESCRIPTION
Name AGND LDOS PWRGOOD CSCS+ PGNDH PGNDL BSTL BSTH VOSENSE VID4 VID3 VID2 VID1 VID0 LDOV GATE Function Small Signal Analog Digital Ground connection Connection Sense Input Input Voltage High Signal VO>setpoint +20% Open collector logic output, high within setpoint Current Sense Input (negative) Current Sense Input (positive) Power Ground High Side Switch High Side Driver Output Power Ground Side Switch Side Driver Output Supply Side Driver Supply High Side Driver Logic shuts down converter; High open normal operation. internal feedback chain Programming Input (MSB) Programming Input Programming Input Programming Input Programming Input (LSB) +12V section Gate Drive Output
View
AGND LDOS PWRGOOD CSCS+ PGNDH PGNDL GATE LDOV VID0 VID1 VID2 VID3 VID4 VOSENSE BSTH BSTL
SOIC)
Note: logic level inputs outputs open collector compatible.
1999 SEMTECH CORP. MITCHELL ROAD NEWBURY PARK 91320
PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER WITH DROPOUT REGULATOR CONTROLLER
SC1172/3
OUTPUT VOLTAGE
Unless specified: 4.75V 5.25V; PGND VOSENSE (CSp-CSm) 60mV; 25oC
PARAMETER Output Voltage
CONDITIONS Application Circuit
43210 01111 01110 01101 01100 01011 01010 01001 01000 00111 00110 00101 00100 00011 00010 00001 00000 11111 11110 11101 11100 11011 11010 11001 11000 10111 10110 10101 10100 10011 10010 10001 10000
1.287 1.336 1.386 1.435 1.485 1.534 1.584 1.633 1.683 1.732 1.782 1.831 1.881 1.930 1.980 2.029 1.980 2.079 2.178 2.277 2.376 2.475 2.574 2.673 2.772 2.871 2.970 3.069 3.168 3.267 3.366 3.465
1.300 1.350 1.400 1.450 1.500 1.550 1.600 1.650 1.700 1.750 1.800 1.850 1.900 1.950 2.000 2.050 2.000 2.100 2.200 2.300 2.400 2.500 2.600 2.700 2.800 2.900 3.000 3.100 3.200 3.300 3.400 3.500
1.313 1.364 1.414 1.465 1.515 1.566 1.616 1.667 1.717 1.768 1.818 1.869 1.919 1.970 2.020 2.071 2.020 2.121 2.222 2.323 2.424 2.525 2.626 2.727 2.828 2.929 3.030 3.131 3.232 3.333 3.434 3.535
UNITS
1999 SEMTECH CORP. MITCHELL ROAD NEWBURY PARK 91320
0.1uF VID0 SENSE PWRGOOD VID4 1500uF 1500uF BUK556 BSTH PGNDH BSTL LDOV LDOS BUK556 5mOhm 1500uF VID1 VID2 VID3 AGND PGNDL GATE SC1172/3CS 1500uF BUK556 1.00k 2.32k
1999 SEMTECH CORP.
0.1uF
APPLICATION CIRCUIT
1500uF
1500uF
VCC_CORE
0.1uF
VID0
0.1uF
VID1
VID2
VID3
VID4
VLIN
PWRGD
330uF 330uF
330uF
PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER WITH DROPOUT REGULATOR CONTROLLER
VINLIN (NORMALLY 3.3V)
100k
NOTE:
SC1172, REQUIRED. CONNECT LDOS (PIN4) DIRECTLY VLIN GENERATE 1.5V OUTPUT. "SETTING OUTPUT VOLTAGE" TABLE. REQUIRED VINLIN PRESENT WITHOUT BEING PRESENT.
SC1172/3
MITCHELL ROAD NEWBURY PARK 91320
PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER WITH DROPOUT REGULATOR CONTROLLER
SC1172/3
MATERIALS LIST
Qty. Reference Part/Description Vendor Various SANYO Various Turns 16AWG MICROMETALS T50-52D core notes Various Various Various Various Various Various SEMTECH Table (Not required SC1172) Table (Not required SC1172) selection requires trade-off between efficiency cost. Absolute maximum RDS(ON) Q1,Q2 OAR-1 Series MV-GX equiv. Notes
C1,C5,C13,C 0.1µF Ceramic C2,C3,C14C17 C11,C12, Q1,Q2,Q3 1500µF/6.3V 330µF/6.3V notes 2.32k, 1/8W 1/8W 1/8W 1/8W 1/8W 100K, 1/8W SC1172/3CSW
SETTING OUTPUT VOLTAGE
3.45V 3.30V 3.10V 2.90V 2.80V 2.50V 1.50V 97.6 18.7
VOUT
1.265 (IFB
Where Feedback bias current feedback resistor Bottom feedback resistor layout diagram clarification must enough that (IFB term does cause significant error
1999 SEMTECH CORP. MITCHELL ROAD NEWBURY PARK 91320
PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER WITH DROPOUT REGULATOR CONTROLLER
SC1172/3
Efficiency
Efficiency
3.5V 3.5V Sync 3.5V Sync
2.8V 2.8V Sync 2.8V Sync
(Amps)
(Amps)
Typical Efficiency Vo=3.5V
Typical Efficiency Vo=2.8V
Efficiency
Efficiency
2.5V 2.5V Sync 2.5V Sync
2.0V 2.0V Sync 2.0V Sync
(Amps)
(Amps)
Typical Efficiency Vo=2.5V
Typical Efficiency Vo=2.0V
Typical Ripple, Vo=2.8V, Io=10A
Transient Response Vo=2.8V, Io=300mA
1999 SEMTECH CORP. MITCHELL ROAD NEWBURY PARK 91320
PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER WITH DROPOUT REGULATOR CONTROLLER
SC1172/3
LAYOUT GUIDELINES
Careful attention layout requirements necessary successful implementation SC1172/3 controller. High currents switching 200kHz present application their effect ground plane voltage differentials must understood minimized. high power parts circuit should laid first. ground plane should used, number position ground plane interruptions should such unnecessarily compromise ground plane integrity. Isolated semi-isolated areas ground plane deliberately introduced constrain ground currents particular areas, example input capacitor bottom ground. loop formed Input Capacitor(s) (Cin), (Q1) Bottom (Q2) must kept
small possible. This loop contains high current, fast transition switching. Connections should wide short possible minimize loop inductance. Minimizing this loop area will reduce EMI, lower ground injection currents, resulting electrically "cleaner" grounds rest system minimize source ringing, resulting more reliable gate switching signals. connection between junction output inductor should wide trace copper region. should short practical. Since this connection fast voltage transitions, keeping this connection short will minimize EMI. connection between output inductor sense resistor should wide trace copper area, there fast voltage current transitions this connection length important, however adding unnecessary impedance will reduce efficiency.
0.1uF 0.1uF
AGND LDOS PWRGOOD CSCS+ PGNDH PGNDL GATE LDOV VID0 VID1 VID2 VID3 VID4 SENSE BSTH BSTL
Cout 1.00k 5mOhm Vout 2.32k
SC1172/3
Heavy lines indicate
Cout
high current paths.
SC1172, required. LDOS connects
Layout diagram SC1172/3
1999 SEMTECH CORP. MITCHELL ROAD NEWBURY PARK 91320
PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER WITH DROPOUT REGULATOR CONTROLLER
October 1999 Output Capacitor(s) (Cout) should located close load possible, fast transient load currents supplied Cout only, connections between Cout load must short, wide copper areas minimize inductance resistance. SC1172/3 best placed over quite ground plane area, avoid pulse currents Cin, loop flowing this area. PGNDH PGNDL should returned ground plane close package. AGND should connected ground side (one output capacitor(s). this possible, AGND connected ground path between Output Capacitor(s) Cin, loop. Under circumstances should AGND returned ground inside Cin, loop. SC1172/3 should supplied from
SC1172/3
supply through resistor, should decoupled directly AGND 0.1µF ceramic capacitor, trace lengths should short possible. Current Sense resistor divider across should form small loop possible, traces running back SC1172/3 should parallel close each other. 0.1µF capacitor should mounted close pins possible. Ideally, ground section should returned ground side (one switching section output capacitor(s).
Vout
Currents various parts power section
1999 SEMTECH CORP. MITCHELL ROAD NEWBURY PARK 91320
PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER WITH DROPOUT REGULATOR CONTROLLER
SC1172/3
COMPONENT SELECTION
SWITCHING SECTION OUTPUT CAPACITORS Selection begins with most critical component. Because fast transient load current requirements modern microprocessor core supplies, output capacitors must supply transient load current requirements until current output inductor ramps level. Output capacitor therefore most important criteria. maximum simply calculated from:
fast enough reduce voltage dropped across faster rate than capacitor sags, hence ensuring good recovery from transient with additional excursions. must also concerned with ripple current output inductor general rule thumb been allow maximum output current ripple current. Note that most output voltage ripple produced inductor ripple current flowing output capacitor ESR. Ripple current calculated from:
ILRIPPLE=
fOSC
Where Maximum transient voltage excursion Transient current step
example, meet 100mV transient limit with load step, output capacitor must less than 10m. meet this kind level, there three available capacitor technologies:
Each Capacitor Technology Tantalum OS-CON Aluminum (µF) 1500 Qty. Rqd. Total (µF) 2000 7500
Ripple current allowance will define minimum permitted inductor value. POWER FETS FETs chosen based several criteria with probably most important being power dissipation power handling capability. power dissipation combination conduction losses, switching losses bottom body diode recovery losses. Conduction losses simply calculated
PCOND RDS(on)
where duty cycle
Switching losses estimated assuming switching time, assume 100ns then:
choice which simply cost /performance issue, with Aluminum being cheapest, taking most space. INDUCTOR Having decided suitable type value output capacitor, maximum allowable value inductor calculated. large inductor will produce slow current ramp rate will cause output capacitor supply more transient load current longer leading output voltage below excursion calculated above. maximum inductor value calculated from:
more generally,
fOSC
(VIN
Body diode recovery losses more difficult estimate, first approximation, reasonable assume that stored charge bottom body diode will moved through starts turn resulting power dissipation will
fOSC
first order approximation, convenient only consider conduction losses determine suitability. 2.8V 14.2A requirement, typical losses would
calculated maximum inductor value assumes 100% duty cycle, some allowance must made. Choosing inductor value calculated maximum will guarantee that inductor current will ramp
1999 SEMTECH CORP. MITCHELL ROAD NEWBURY PARK 91320
PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER WITH DROPOUT REGULATOR CONTROLLER
October 1999 type RDS(on) 2.48 0.79 1.53 Package TO220 SO-8
SC1172/3
BUK556H IRL2203 Si4410 13.5
BOTTOM Bottom losses almost entirely conduction. body diode forced into conduction beginning bottom switch conduction period, when turns off, there very little voltage across resulting switching losses. Conduction losses determined
PCOND RDS(
INPUT CAPACITORS since ripple current input capacitors high output current, suitable capacitors must chosen accordingly. Also, during fast load transients, there restrictions input di/dt. These restrictions require useable energy storage within converter circuitry, either extra output capacitance more usually, additional input capacitors. Choosing input capacitors will help maximize ripple rating given size.
example above: type RDS(on) 1.95 0.62 1.20 13.5 Package TO220 SO-8
BUK556H IRL2203 Si4410
Each package types characteristic thermal impedance, TO-220 package, thermal impedance mostly determined heatsink used. surface mount packages double sided FR4, printed circuit board material, thermal impedances SO-8 readily achievable. corresponding temperature rise detailed below: Temperature rise type
Bottom 39.0 24.8
BUK556H 49.6 IRL2203 Si4410
31.6 122.4
With Heatsink apparent that single SO-8 Si4410 adequate this application, using parallel pairs each position, power dissipation will approximately halved temperature rise reduced factor
1999 SEMTECH CORP. MITCHELL ROAD NEWBURY PARK 91320
PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER WITH DROPOUT REGULATOR CONTROLLER
SC1172/3
OUTLINE DRAWING
JEDEC MS-013AD B17104B
ECN99-667
1999 SEMTECH CORP. MITCHELL ROAD NEWBURY PARK 91320
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