Buck Synchronous-Rectifier Pulse-Width Modulator (PWM) Controller

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Buck Synchronous-Rectifier Pulse-Width Modulator (PWM) Controller

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HIP6012
Buck Synchronous-Rectifier Pulse-Width Modulator (PWM) Controller
HIP6012 provides complete control protection DC-DC converter optimized high-performance microprocessor applications. designed drive N-Channel MOSFETs synchronous-rectified buck topology. HIP6012 integrates control, output adjustment, monitoring protection functions into single package. output voltage converter precisely regulated 1.27V, with maximum tolerance ±1.5% over temperature line voltage variations. HIP60012 provides simple, single feedback loop, voltage-mode control with fast transient response. includes 200kHz free-running triangle-wave oscillator that adjustable from below 50kHz over 1MHz. error amplifier features 15MHz gain-bandwidth product 6V/µs slew rate which enables high converter bandwidth fast transient performance. resulting duty ratio ranges from 100%. HIP6012 protects against over-current conditions inhibiting operation. HIP6012 monitors current using rDS(ON) upper MOSFET which eliminates need current sensing resistor.
June 1997
Features
Drives N-Channel MOSFETs Operates From +12V Input Simple Single-Loop Control Design Voltage-Mode Control Fast Transient Response High-Bandwidth Error Amplifier Full 100% Duty Ratio Excellent Output Voltage Regulation 1.27V Internal Reference ±1.5% Over Line Voltage Temperature Over-Current Fault Monitor Does Require Extra Current Sensing Element Uses MOSFET's rDS(ON) Small Converter Size Constant Frequency Operation 200kHz Free-Running Oscillator Programmable from 50kHz Over 1MHz Pin, SOIC Package
Applications
Power Supply PentiumTM, PentiumPro, PowerPCand AlphaMicroprocessors High-Power 3.xV DC-DC Regulators Low-Voltage Distributed Power Supplies
Pinout
HIP6012 (SOIC) VIEW
PVCC LGATE PGND BOOT UGATE PHASE
Ordering Information
PART NUMBER HIP6012CB TEMP. RANGE (oC) PACKAGE SOIC PKG. M14.15
OCSET COMP
PowerPCis trademark IBM. Alphais trademark Digital Equipment Corporation. Pentiumis trademark Intel Corporation. CAUTION: These devices sensitive electrostatic discharge. Users should follow proper Handling Procedures. Copyright
Harris Corporation 1997
File Number
4324
HIP6012 Typical Application
+12V OCSET MONITOR PROTECTION BOOT +12V
UGATE PHASE PVCC +12V
HIP6012
LGATE PGND
COMP
Block Diagram
POWER-ON RESET (POR) 10µA OCSET
OVERCURRENT
SOFTSTART
BOOT UGATE PHASE
200µA
1.27 VREF REFERENCE
COMPARATOR
INHIBIT
COMP
ERROR
GATE CONTROL LOGIC
PVCC LGATE PGND
OSCILLATOR
HIP6012
Absolute Maximum Ratings
Supply Voltage, VCC. +15.0V Boot Voltage, VBOOT VPHASE +15.0V Input, Output Voltage -0.3V +0.3V Classification Class
Thermal Information
Thermal Resistance (Typical, Note (oC/W) SOIC Package Maximum Junction Temperature 150oC Maximum Storage Temperature Range .-65oC 150oC Maximum Lead Temperature (Soldering 10s) 300oC (Lead tips only)
Recommended Operating Conditions
Supply Voltage, VCC. +12V ±10% Ambient Temperature Range .0oC 70oC Junction Temperature Range .0oC 125oC
CAUTION: Stresses above those listed "Absolute Maximum Ratings" cause permanent damage device. This stress only rating operation device these other conditions above those indicated operational sections this specification implied.
NOTE: measured with component mounted evaluation board free air.
Electrical Specifications
PARAMETER SUPPLY CURRENT Nominal Supply Shutdown Supply POWER-ON RESET Rising Threshold Falling Threshold Enable Input threshold Voltage Rising VOCSET Threshold OSCILLATOR Free Running Frequency Total Variation Ramp Amplitude REFERENCE Reference Voltage ERROR AMPLIFIER Gain Gain-Bandwidth Product Slew Rate GATE DRIVERS Upper Gate Source Upper Gate Sink Lower Gate Source Lower Gate Sink PROTECTION OCSET Current Source Soft Start Current
Recommended Operating Conditions, Unless Otherwise Noted SYMBOL TEST CONDITIONS UNITS
VCC; UGATE LGATE Open
VOCSET 4.5VDC VOCSET 4.5VDC VOCSET 4.5VDC
1.27
10.4
OPEN, 200k VOSC OPEN
VP-P
1.251
1.270
1.289
COMP 10pF
V/µs
IUGATE RUGATE ILGATE RLGATE
VBOOT VPHASE 12V, VUGATE ILGATE 0.3A 12V, VLGATE ILGATE 0.3A
IOCSET
VOCSET 4.5VDC
HIP6012 Typical Performance Curves
RESISTANCE 1000 PULLUP +12V IVCC (mA) CGATE 3300pF CGATE 10pF SWITCHING FREQUENCY (kHz) 1000 CGATE 1000pF
PULLDOWN
SWITCHING FREQUENCY (kHz)
1000
FIGURE RESISTANCE FREQUENCY
FIGURE BIAS SUPPLY CURRENT FREQUENCY
Functional OCSET COMP PVCC LGATE PGND BOOT UGATE PHASE
COMP (Pin (Pin COMP available external pins error amplifier. inverting input error amplifier COMP error amplifier output. These pins used compensate voltage-control feedback loop converter. (Pin This open-collector enable pin. Pull this below disable converter. shutdown, soft start discharged UGATE LGATE pins held low. (Pin Signal ground voltage levels measured with respect this pin. PHASE (Pin Connect PHASE upper MOSFET source. This used monitor voltage drop across MOSFET over-current protection. This also provides return path upper gate drive. UGATE (Pin Connect UGATE upper MOSFET gate. This provides gate drive upper MOSFET. BOOT (Pin This provides bias voltage upper MOSFET driver. bootstrap circuit used create BOOT voltage suitable drive standard N-Channel MOSFET. PGND (Pin This power ground connection. lower MOSFET source this pin. LGATE (Pin Connect LGATE lower MOSFET gate. This provides gate drive lower MOSFET. PVCC (Pin Provide bias supply lower gate drive this pin. (Pin Provide bias supply chip this pin.
(Pin This provides oscillator switching frequency adjustment. placing resistor (RT) from this GND, nominal 200kHz switching frequency increased according following equation:
200kHz
GND)
Conversely, connecting pull-up resistor (RT) from this reduces switching frequency according following equation.:
200kHz
12V)
OCSET (Pin Connect resistor (ROCSET) from this drain upper MOSFET. ROCSET, internal 200µA current source (IOCS), upper MOSFET on-resistance (rDS(ON)) converter over-current (OC) trip point according following equation:
ROCSET PEAK
over-current trip cycles soft-start function. (Pin Connect capacitor from this ground. This capacitor, along with internal 10µA current source, sets softstart interval converter.
HIP6012 Functional HIP6012 automatically initializes upon receipt power. Special sequencing input supplies necessary. Power-On Reset (POR) function continually monitors input supply voltages enable (EN) pin. monitors bias voltage input voltage (VIN) OCSET pin. level OCSET equal Less fixed voltage drop (see over-current protection). With held VCC, function initiates soft start operation after both input supply voltages exceed their thresholds. operation with single +12V power source, equivalent +12V power source must exceed rising threshold before initiates operation. Power-On Reset (POR) function inhibits operation with chip disabled low). With both input supplies above their thresholds, transitioning high initiates soft start interval. Soft Start function initiates soft start sequence. internal 10µA current source charges external capacitor (CSS) Soft start clamps error amplifier output (COMP pin) reference input terminal error amp) voltage. Figure shows soft start interval with 0.1µF. Initially clamp error amplifier (COMP pin) controls converter's output voltage. Figure voltage reaches valley oscillator's triangle wave. oscillator's triangular waveform compared ramping error amplifier voltage. This generates PHASE pulses increasing width that charge output capacitor(s). This interval increasing pulse width continues With sufficient output voltage, clamp reference input controls output voltage. This interval between Figure voltage exceeds reference voltage output voltage regulation. This method provides rapid controlled output voltage rise.
SOFT-START OUTPUT INDUCTOR
Initialization
TIME (20ms/DIV)
FIGURE OVER-CURRENT OPERATION
Over-Current Protection
over-current function protects converter from shorted output using upper MOSFET's on-resistance, rDS(ON) monitor current. This method enhances converter's efficiency reduces cost eliminating current sensing resistor. over-current function cycles soft-start function hiccup mode provide fault protection. resistor (ROCSET) programs over-current trip level. internal 200µA (typical) current sink develops voltage across ROCSET that reference VIN. When voltage across upper MOSFET (also referenced VIN) exceeds voltage across ROCSET, over-current function initiates soft-start sequence. soft-start function discharges with 10µA current sink inhibits operation. soft-start function recharges CSS, operation resumes with error amplifier clamped voltage. Should overload occur while recharging CSS, soft start function inhibits operation while fully charging complete cycle. Figure shows this operation with overload condition. Note that inductor current increases over during charging interval causes over-current trip. converter dissipates very little power with this method. measured input power conditions Figure 2.5W. over-current function will trip peak inductor current (IPEAK) determined
SOFT-START (1V/DIV)
OUTPUT VOLTAGE (1V/DIV)
OCSET ROCSET PEAK
TIME (5ms/DIV)
where IOCSET internal OCSET current source (200µA typical). trip point varies mainly MOSFET's rDS(ON) variations. avoid over-current tripping normal operating load range, find ROCSET resistor from equation above with:
FIGURE SOFT-START INTERVAL
HIP6012
maximum rDS(ON) highest junction temperature. minimum IOCSET from specification table. Determine PEAK PEAK where output inductor ripple current. equation ripple current section under component guidelines titled `Output Inductor Selection'. small ceramic capacitor should placed parallel with ROCSET smooth voltage across ROCSET presence switching noise input voltage. HIP6012
+12V CVCC
only 10µA. Provide local decoupling between pins. Locate capacitor, CBOOT close practical BOOT PHASE pins.
BOOT CBOOT PHASE LOAD VOUT (PARASITIC) VE/A +VIN VOUT
Application Guidelines
Layout Considerations high frequency switching converter, layout very important. Switching current from power device another generate voltage transients across impedances interconnecting bond wires circuit traces. These interconnecting impedances should minimized using wide, short printed circuit traces. critical components should located close together possible using ground plane construction single point grounding.
FIGURE PRINTED CIRCUIT BOARD SMALL SIGNAL LAYOUT GUIDELINES
COMPARATOR VOSC DRIVER DRIVER PHASE
HIP6012
UGATE PHASE LGATE PGND
ERROR VOUT
REFERENCE
LOAD
DETAILED COMPENSATION COMPONENTS VOUT
RETURN COMP
FIGURE PRINTED CIRCUIT BOARD POWER GROUND PLANES ISLANDS
Figure shows critical power components converter. minimize voltage overshoot interconnecting wires indicated heavy lines should part ground power plane printed circuit board. components shown Figure should located close together possible. Please note that capacitors each represent numerous physical capacitors. Locate HIP6012 within inches MOSFETs, circuit traces MOSFETs' gate source connections from HIP6012 must sized handle peak current. Figure shows circuit traces that require additional layout consideration. single point ground plane construction circuits shown. Minimize leakage current paths locate capacitor, close because internal current source
HIP6012
FIGURE VOLTAGE MODE BUCK CONVERTER COMPENSATION DESIGN
Feedback Compensation Figure highlights voltage-mode control loop synchronous-rectified buck converter. output voltage (Vout) regulated Reference voltage level. error amplifier (Error Amp) output (VE/A) compared with oscillator (OSC) triangular wave provide pulse-width modulated (PWM) wave with amplitude PHASE node. wave smoothed output filter CO).
HIP6012
modulator transfer function small-signal transfer function Vout/VE/A. This function dominated Gain output filter CO), with double pole break frequency zero FESR. Gain modulator simply input voltage (VIN) divided peak-to-peak oscillator voltage VOSC. Modulator Break Frequency Equations
GAIN (dB) MODULATOR GAIN FESR 100K 20LOG (R2/R1) OPEN LOOP ERROR GAIN
20LOG (VIN/VOSC) COMPENSATION GAIN CLOSED LOOP GAIN
compensation network consists error amplifier (internal HIP6012) impedance networks ZFB. goal compensation network provide closed loop transfer function with highest crossing frequency (f0dB) adequate phase margin. Phase margin difference between closed loop phase f0dB 180o. equations below relate compensation network's poles, zeros gain components (R1, Figure these guidelines locating poles zeros compensation network: Compensation Break Frequency Equations
FREQUENCY (Hz)
FIGURE ASYMPTOTIC BODE PLOT CONVERTER GAIN
compensation gain uses external impedance networks provide stable, high bandwidth (BW) overall loop. stable control loop gain crossing with -20dB/decade slope phase margin greater than 45o. Include worst case component variations when determining phase margin.
Component Selection Guidelines
Output Capacitor Selection output capacitor required filter output supply load transient current. filtering requirements function switching frequency ripple current. load transient requirements function slew rate (di/dt) magnitude transient load current. These requirements generally with capacitors careful layout. Modern microprocessors produce transient load rates above 1A/ns. High frequency capacitors initially supply transient slow current load rate seen bulk capacitors. bulk filter capacitor values generally determined (effective series resistance) voltage rating requirements rather than actual capacitance requirements. High frequency decoupling capacitors should placed close power pins load physically possible. careful inductance circuit board wiring that could cancel usefulness these inductance components. Consult with manufacturer load specific decoupling requirements. example, Intel recommends that high frequency decoupling Pentium-Pro composed least forty (40) 1.0µF ceramic capacitors 1206 surface-mount package. only specialized low-ESR capacitors intended switching-regulator applications bulk capacitors. bulk capacitor's will determine output ripple voltage initial voltage drop after high slew-rate transient. aluminum electrolytic capacitor's value related case size with lower available larger case sizes. However, equivalent series inductance (ESL) these capacitors increases with case size
Pick Gain (R2/R1) desired converter bandwidth Place Zero Below Filter's Double Pole (~75% FLC) Place Zero Filter's Double Pole Place Pole Zero Place Pole Half Switching Frequency Check Gain against Error Amplifier's Open-Loop Gain Estimate Phase Margin Repeat Necessary Figure shows asymptotic plot DC-DC converter's gain frequency. actual Modulator Gain high gain peak high factor output filter shown Figure Using above guidelines should give Compensation Gain similar curve plotted. open loop error amplifier gain bounds compensation gain. Check compensation gain with capabilities error amplifier. Closed Loop Gain constructed log-log graph Figure adding Modulator Gain Compensation Gain dB). This equivalent multiplying modulator transfer function compensation transfer function plotting gain.
HIP6012
reduce usefulness capacitor high slew-rate transient loading. Unfortunately, specified parameter. Work with your capacitor supplier measure capacitor's impedance with frequency select suitable component. most cases, multiple electrolytic capacitors small case size perform better than single large case capacitor. Output Inductor Selection output inductor selected meet output voltage ripple requirements minimize converter's response time load transient. inductor value determines converter's ripple current ripple voltage function ripple current. ripple voltage current approximated following equations:
tion, select bulk capacitor with voltage current ratings above maximum input voltage largest current required circuit. capacitor voltage rating should least 1.25 times greater than maximum input voltage voltage rating times conservative guideline. current rating requirement input capacitor buck regulator approximately load current. through hole design, several electrolytic capacitors (Panasonic series Nichicon series Sanyo MVGX equivalent) needed. surface mount designs, solid tantalum capacitors used, caution must exercised with regard capacitor surge current rating. These capacitors must capable handling surge-current power-up. series available from AVX, 593D series from Sprague both surge current tested. MOSFET Selection/Considerations
VOUT
Increasing value inductance reduces ripple current voltage. However, large inductance values reduce converter's response time load transient. parameters limiting converter's response load transient time required change inductor current. Given sufficiently fast control loop design, HIP6012 will provide either 100% duty cycle response load transient. response time time required slew inductor current from initial current value transient current level. During this interval difference between inductor current transient current level must supplied output capacitor. Minimizing response time minimize output capacitance required. response time transient different application load removal load. following equations give approximate response time interval application removal transient load:
TRAN RISE TRAN
HIP6012 requires N-Channel power MOSFETs. These should selected based upon rDS(ON), gate supply requirements, thermal management requirements. high-current applications, MOSFET power dissipation, package selection heatsink dominant design factors. power dissipation includes loss components; conduction loss switching loss. conduction losses largest component power dissipation both upper lower MOSFETs. These losses distributed between MOSFETs according duty factor (see equations below). Only upper MOSFET switching losses, since Schottky rectifier clamps switching node before synchronous rectifier turns
PUPPER rDS(ON) PLOWER rDS(ON)
Where: duty cycle VIN, switching interval, switching frequency. These equations assume linear voltage-current transitions adequately model power loss reverserecovery lower MOSFET's body diode. gate-charge losses dissipated HIP6012 don't heat MOSFETs. However, large gate-charge increases switching interval, which increases upper MOSFET switching losses. Ensure that both MOSFETs within their maximum junction temperature high ambient temperature calculating temperature rise according package thermal-resistance specifications. separate heatsink necessary depending upon MOSFET power, package type, ambient temperature flow. Standard-gate MOSFETs normally recommended with HIP6012. However, logic-level gate MOSFETs used under special circumstances. input voltage, upper gate drive level, MOSFET's absolute gate-tosource voltage rating determine whether logic-level MOSFETs appropriate.
where: ITRAN transient load current step, tRISE response time application load, tFALL response time removal load. With input source, worst case response time either application removal load dependent upon output voltage setting. sure check both these equations minimum maximum output levels worst case response time. Input Capacitor Selection input bypass capacitors control voltage overshoot across MOSFETs. small ceramic capacitors high frequency decoupling bulk capacitors supply current needed each time turns Place small ceramic capacitors physically close MOSFETs between drain source important parameters bulk input capacitor voltage rating current rating. reliable opera-
HIP6012
Figure shows upper gate drive (BOOT pin) supplied bootstrap circuit from boot capacitor, CBOOT develops floating supply voltage referenced PHASE pin. This supply refreshed each cycle voltage less boot diode drop (VD) when lower MOSFET, turns logic-level MOSFET only used MOSFET's absolute gate-to-source voltage rating exceeds maximum voltage applied logic-level MOSFET used absolute gate-tosource voltage rating exceeds maximum voltage applied PVCC.
+12V DBOOT BOOT +12V +12V LESS
HIP6012
BOOT UGATE PHASE +12V NOTE: VG-S PVCC NOTE: VG-S
PVCC
LGATE PGND
HIP6012
UGATE PHASE
CBOOT
FIGURE UPPER GATE DRIVE DIRECT DRIVE OPTION
NOTE: VG-S
Schottky Selection Rectifier clamp that catches negative inductor swing during dead time between turning lower MOSFET turning upper MOSFET. diode must Schottky type prevent lossy parasitic MOSFET body diode from conducting. acceptable omit diode body diode lower MOSFET clamp negative inductor swing, efficiency will drop percent result. diode's rated reverse breakdown voltage must greater than maximum input voltage.
PVCC +12V LGATE PGND NOTE: VG-S PVCC
FIGURE UPPER GATE DRIVE BOOTSTRAP OPTION
Figure shows upper gate drive supplied direct connection This option should only used converter systems where main input voltage less. peak upper gate-to-source voltage approximately less input supply. main power bias, gate-to-source voltage logic-level MOSFET good choice logiclevel MOSFET used absolute gate-tosource voltage rating exceeds maximum voltage applied PVCC.
HIP6012 HIP6012 DC-DC Converter Application Circuit
figure below shows DC-DC converter circuit microprocessor application, originally designed employ HIP6006 controller. Given similarities between HIP6006 HIP6012 controllers, circuit implemented using HIP6012 controller without modifications. However, given expanded reference voltage tolerance range, HIP6012-based converter require additional output capacitance. Detailed information circuit, including complete Bill-of-Materials circuit board description, found application note AN9722. Harris' home page web: http://www.semi.harris.com Harris AnswerFAX (407-724-7800) document 99722.
12VCC C1-3 680µF C17-18 1206
ENABLE
1206
MONITOR PROTECTION OCSET BOOT UGATE PHASE PVCC 0.1µF VOUT C6-9 1000µF 1000pF 3.01k 4148
PHASE
0.1µF
SPARE
HIP6012
COMP
LGATE PGND
-C14
33pF 0.01µF SPARE SPARE
COMP
Component Selection Notes: C1-C3 each 680µF 25WVDC, Sanyo MV-GX equivalent C6-C9 each 1000µF 6.3WVDC, Sanyo MV-GX equivalent Core: Micrometals T50-52B; Winding: Turns 17AWG 1N4148 equivalent Schottky, Motorola MBR340 equivalent Harris MOSFET; RFP25N05
FIGURE DC-DC CONVERTER APPLICATION CIRCUIT
HIP6012 Small Outline Plastic Packages (SOIC)
INDEX AREA SEATING PLANE 0.25(0.010)
M14.15 (JEDEC MS-012-AB ISSUE
LEAD NARROW BODY SMALL OUTLINE PLASTIC PACKAGE INCHES SYMBOL
MILLIMETERS 1.35 0.10 0.33 0.19 8.55 3.80 1.75 0.25 0.51 0.25 8.75 4.00 NOTES Rev. 12/93
0.0532 0.0040 0.013 0.0075 0.3367 0.1497
0.0688 0.0098 0.020 0.0098 0.3444 0.1574
0.10(0.004)
0.050 0.2284 0.0099 0.016 0.2440 0.0196 0.050
1.27 5.80 0.25 0.40 6.20 0.50 1.27
0.25(0.010)
NOTES: Symbols defined Series Symbol List" Section Publication Number Dimensioning tolerancing ANSI Y14.5M-1982. Dimension does include mold flash, protrusions gate burrs. Mold flash, protrusion gate burrs shall exceed 0.15mm (0.006 inch) side. Dimension does include interlead flash protrusions. Interlead flash protrusions shall exceed 0.25mm (0.010 inch) side. chamfer body optional. present, visual index feature must located within crosshatched area. length terminal soldering substrate. number terminal positions. Terminal numbers shown reference only. lead width "B", measured 0.36mm (0.014 inch) greater above seating plane, shall exceed maximum value 0.61mm (0.024 inch). Controlling dimension: MILLIMETER. Converted inch dimensions necessarily exact.
Harris Semiconductor products manufactured, assembled tested under ISO9000 quality systems certification.
Harris Semiconductor products sold description only. Harris Semiconductor reserves right make changes circuit design and/or specifications time without notice. Accordingly, reader cautioned verify that data sheets current before placing orders. Information furnished Harris believed accurate reliable. However, responsibility assumed Harris subsidiaries use; infringements patents other rights third parties which result from use. license granted implication otherwise under patent patent rights Harris subsidiaries.
Sales Office Headquarters
general information regarding Harris Semiconductor products, call 1-800-4-HARRIS NORTH AMERICA Harris Semiconductor 883, Mail Stop 53-210 Melbourne, 32902 TEL: 1-800-442-7747 (407) 729-4984 FAX: (407) 729-5321 EUROPE Harris Semiconductor Mercure Center 100, Fusee 1130 Brussels, Belgium TEL: (32) 2.724.2111 FAX: (32) 2.724.22.05 ASIA Harris Semiconductor Ltd. Tannery Road Cencon #09-01 Singapore 1334 TEL: (65) 748-4200 FAX: (65) 748-0400

Buck Synchronous-Rectifier Pulse-Width Modulator (PWM) Controller

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