SC1186 DESCRIPTION SC1186 combines synchronous voltage mode
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PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER, DUAL DROPOUT REGULATOR CONTROLLER
SC1186
DESCRIPTION
SC1186 combines synchronous voltage mode controller with low-dropout linear regulators providing most circuitry necessary implement three DC/DC converters powering advanced microprocessors such Pentium III. SC1186 switching section features integrated converter, latched drive output enhanced noise immunity, pulse pulse current limiting logic compatible shutdown. SC1186 switching section operates fixed frequency 140kHz, 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. SC1186 linear sections dropout regulators with short circuit protection, supplying 1.5V 2.5V non-GTL I/O. Reference voltage made available external linear regulators.
FEATURES
Synchronous design, enables heatsink solution efficiency (switching section) output programmability Designed Intel Pentium requirements 1.5V, 2.5V short circuit protected linear controllers 1.265V 1.5% Reference available
APPLICATIONS
Pentium microprocessor supplies Flexible motherboards 1.3V 3.5V microprocessor supplies Programmable triple power supplies
ORDERING INFORMATION
Part Number
Package
Linear Voltage
Temp. Range
SC1186CSW
SO-24
1.5V/2.5V 125°C
Note: suffix `TR' tape reel.
CONFIGURATION
BLOCK DIAGRAM
CURRENT LIMIT
View
BSTH
70mV
AGND GATE1 LDOS1 LDOS2 LDOEN CSCS+ PGNDH PGNDL
GATE2 LDOV VID0 VID1 VID2 VID3 VID4 VOSENSE BSTH BSTL
VID4 VID3 VID2 VID1 VID0 VOSENSE
LEVEL SHIFT HIGH SIDE DRIVE
ERROR
PGNDH
OSCILLATOR
SHOOT-THRU CONTROL
AGND
LDOEN LDOS1
2.5V CONTROLLER 1.5V CONTROLLER SYNCHRONOUS MOSFET DRIVE
BSTL
SOIC)
GATE1
1.265V
PGNDL LDOV GATE2 LDOS2
Pentium registered trademark Intel Corporation
1999 SEMTECH CORP.
MITCHELL ROAD NEWBURY PARK 91320
PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER, DUAL DROPOUT REGULATOR CONTROLLER
SC1186
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 Symbol Maximum -0.3 -0.3 +125 +150 Units °C/W °C/W
TSTG
ELECTRICAL CHARACTERISTICS
Unless specified: 4.75V 5.25V; PGND VOSENSE (CS+-CS-) 60mV; LDOV 11.4V 12.6V; 70°C
PARAMETER Switching Section Output Voltage Supply Voltage Supply Current Load Regulation Line Regulation Current Limit Voltage Oscillator Frequency Oscillator Duty Cycle Peak Sink/Source Current Peak Sink/Source Current Gain (AOL) Source Current Leakage Power Good Threshold Voltage Dead Time Linear Sections Quiescent Current Output Voltage LDO1 Output Voltage LDO2 Reference Voltage Gain (AOL) Load Regulation Line Regulation Output Impedance
CONDITIONS Application Circuit 5.0V 0.8A
UNITS
BSTH-DH 4.5V, DH-PGNDH 3.3V DH-PGNDH 1.5V BSTL-DL 4.5V, DL-PGNDL 3.3V DL-PGNDL 1.5V VOSENSE VIDx 2.4V VIDx
Output Voltage Table ±0.15
LDOV
Iref 100µA LDOS (1,2) GATE (1,2) VGATE 6.5V
2.493 2.525 2.556 1.496 1.515 1.534 1.246 1.265 1.284
1999 SEMTECH CORP. MITCHELL ROAD NEWBURY PARK 91320
PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER, DUAL DROPOUT REGULATOR CONTROLLER
SC1186
ELECTRICAL CHARACTERISTICS (Cont.)
Unless specified: 4.75V 5.25V; PGND VOSENSE (CS+-CS-) 60mV; LDOV 11.4V 12.6V; 70°C
PARAMETER LDOV Undervoltage Lockout LDOEN Threshold LDOEN Sink Current Overcurrent Trip Voltage Power-up Output Short Circuit Immunity Output Short Circuit Glitch Immunity Gate Pulldown Impedance VOSENSE Impedance
CONDITIONS
0.01 -200
UNITS -300
LDOEN 3.3V LDOEN point
GATE(1,2)-AGND;VCC=BST=0V
DESCRIPTION
Name AGND GATE1 LDOS1 LDOS2 LDOEN CSCS+ PGNDH PGNDL BSTL BSTH VOSENSE VID4 VID3 VID2 VID1 VID0 LDOV GATE2 Function Small Signal Analog Digital Ground Gate Drive Output LDO1 Sense Input LDO1 Sense Input LDO2 Input Voltage Buffered Reference Voltage output Supply Monitor. 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 LDO2
View
AGND GATE1 LDOS1 LDOS2 LDOEN CSCS+ PGNDH PGNDL
GATE2 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, DUAL DROPOUT REGULATOR CONTROLLER
SC1186
OUTPUT VOLTAGE
Unless specified: 4.75V 5.25V; PGND VOSENSE (CS+-CS-) 60mV; 85°C
PARAMETER Output Voltage
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
1.277 1.326 1.375 1.424 1.478 1.527 1.576 1.625 1.675 1.724 1.782 1.832 1.881 1.931 1.980 2.030 1.970 2.069 2.167 2.266 2.364 2.463 2.561 2.660 2.758 2.842 2.940 3.038 3.136 3.234 3.332 3.430
Standard 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
1.323 1.374 1.425 1.476 1.523 1.573 1.624 1.675 1.726 1.776 1.818 1.869 1.919 1.970 2.020 2.071 2.030 2.132 2.233 2.335 2.436 2.538 2.639 2.741 2.842 2.958 3.060 3.162 3.264 3.366 3.468 3.570
UNITS
1999 SEMTECH CORP. MITCHELL ROAD NEWBURY PARK 91320
1999 SEMTECH CORP.
0.1uF
VID0 VID1 VID2 VID4 LDOEN VOSENSE CSCS+
1.00k 2.32k
APPLICATION CIRCUIT
0.1uF
1500uF 1500uF 1500uF IRL34025 5mOhm 1500uF IRL34025
VID3 AGND PGNDL GATE2 GATE1 LDOS2 LDOS1 LDOV BSTL PGNDH BSTH
1500uF
VCC_CORE
0.1uF VID0 VID1 VID2 VID3 VID4 SC1186CSW
0.1uF 1500uF
2.5V IRLML2803 330uF
3.3V
1.5V
330uF
PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER, DUAL DROPOUT REGULATOR CONTROLLER
IRFZ14S
1000uF
SC1186
MITCHELL ROAD NEWBURY PARK 91320
PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER, DUAL DROPOUT REGULATOR CONTROLLER
SC1186
MATERIALS LIST
Qty. Reference Part/Description Vendor Various SANYO MV-GX equiv. Notes
C1,C5,C13,C18 0.1µF Ceramic C2,C3,C14-C17 1500µF/6.3V C11,C21 Q1,Q2 1000µF 330µF/6.3V notes IRLML2803 IRFZ14S 2.32k, 1/8W 1/8W 1/8W SC1186CSW
Various Turns 16AWG MICROMETALS T50-52D core notes Various Various Various SEMTECH selection requires trade-off between efficiency cost. Absolute maximum RDS(ON) Q1,Q2 SOT23 equivalent) equivalent OAR-1 Series
1999 SEMTECH CORP. MITCHELL ROAD NEWBURY PARK 91320
PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER, DUAL DROPOUT REGULATOR CONTROLLER
SC1186
Efficiency
Vo=2.8V Vo=2.0V Vo=2.5V
(Amps) 10.0 12.0 14.0 16.0
Typical Efficiency (Switching section) Typical Ripple, Vo=2.0V, Io=10A
Output Voltage
Output Current 5A/div
Transient Response Vo=2.4V, Io=300mA
2.5V Linear Short circuit output response
1999 SEMTECH CORP. MITCHELL ROAD NEWBURY PARK 91320
PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER, DUAL DROPOUT REGULATOR CONTROLLER
SC1186
LAYOUT GUIDELINES
Careful attention layout requirements necessary successful implementation SC1186 controller. High currents switching 140kHz 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 GATE1 LDOS1 LDOS2 LDOEN CSCS+ PGNDH PGNDL GATE2 LDOV VID0 VID1 VID2 VID3 VID4 VOSENSE BSTH BSTL
Cout 1.00k 5mOhm Vout 2.32k
SC1186
Heavy lines indicate
3.3V Cout Lin1 Lin1
high current paths.
Lin2 Cout Lin2
Layout diagram SC1186
1999 SEMTECH CORP. MITCHELL ROAD NEWBURY PARK 91320
PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER, DUAL DROPOUT REGULATOR CONTROLLER
PRELIMINARY September 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. SC1186 best placed over quiet 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. SC1186 should supplied from
SC1186
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 SC1186 should parallel close each other. 0.1µF capacitor should mounted close pins possible. Ideally, grounds sections should returned ground side (one output capacitor(s).
Vout
Currents various parts power section
1999 SEMTECH CORP. MITCHELL ROAD NEWBURY PARK 91320
PROGRAMMABLE SYNCHRONOUS DC/DC CONVERTER, DUAL DROPOUT REGULATOR CONTROLLER
SC1186
fast enough reduce voltage dropped across faster rate than capacitor sags, hence enSWITCHING SECTION suring good recovery from transient with additional OUTPUT CAPACITORS Selection begins with excursions. most critical component. Because fast transient load must also concerned with ripple current current requirements modern microprocessor core output inductor general rule thumb been supplies, output capacitors must supply transient allow maximum output current ripple current. load current requirements until current output Note that most output voltage ripple produced inductor ramps level. Output capacitor inductor ripple current flowing output caESR therefore most important criteria. pacitor ESR. Ripple current calculated from: maximum simply calculated from:
COMPONENT SELECTION
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 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
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, DUAL DROPOUT REGULATOR CONTROLLER
PRELIMINARY September 1999 Using 1.5X Room temp RDS(ON) allow temperature rise. type IRL34025 IRL2203 Si4410 RDS(on) 10.5 1.69 1.19 2.26 Package SO-8
SC1186
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(on)
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.
SHORT CIRCUIT PROTECTION LINEARS
Short circuit feature linear controllers implemented using Rds(on) FETs. output current increases, regulation loop maintains output voltage turning more more. Eventually, Rds(on) limit reached, will unably turn more fully, output voltage will start fall. When output voltage falls approximately nominal, controller latched off, setting output voltage Power must cycled reset latch. prevent false latching capacitor inrush currents supply rails, current limit latch initially disabled. enabled preset time (nominally 2mS) after both LDOV LDOEN rails rise above their lockout points. most effective, linear Rds(on) should selected artificially low, should chosen that, maximum required current, almost fully turned example, linear supply 1.5V required from 3.3V rail, allowable Rds(on) would Rds(on)max (0.95*3.3-1.5)/4 400m allow temperature effects 200m would suitable room temperature maximum, allowing peak short circuit current approximately short time before shutdown.
example above: type IRL34025 IRL2203 Si4410 RDS(on) 10.5 1.33 0.93 1.77 Package SO-8
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 IRL34025 IRL2203 Si4410 67.6 47.6 180.8 Bottom 53.2 37.2 141.6
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, DUAL DROPOUT REGULATOR CONTROLLER
SC1186
OUTLINE DRAWING
JEDEC MS-013AD B17104B
ECN99-600
9-22-99
1999 SEMTECH CORP. MITCHELL ROAD NEWBURY PARK 91320
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