Current-Mode Controllers with Integrated Startup Circuit MAX5019/
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Current-Mode Controllers with Integrated Startup Circuit
MAX5019/MAX5020 integrate building blocks necessary implementing DC-DC fixed-frequency power supplies. Either primary- secondaryside regulation used implement isolated nonisolated power supplies. These devices currentmode controllers with integrated high-voltage startup circuit suitable telecom/industrial voltage range power supplies. Current-mode control with leadingedge blanking simplifies control-loop design internal ramp compensation circuitry stabilizes current loop when operating duty cycles above (MAX5019). MAX5019 allows operating duty cycle used implement flyback converters whereas MAX5020 limits operating duty cycle less than used single-ended forward converters. high-voltage startup circuit allows these devices draw power directly from 110V input supply during startup. switching frequency internally trimmed 275kHz ±10%, thus reducing magnetics filter component costs. MAX5019/MAX5020 available 8-pin packages. Warning: MAX5019/MAX5020 operate with high voltages. Exercise caution.
Features
Wide Input Range: (18V 110V) (13V 36V) Isolated (without optocoupler) Nonisolated Power Supply Current-Mode Control Leading-Edge Blanking Internally Trimmed 275kHz ±10% Oscillator External Component Count Soft-Start High-Voltage Startup Circuit Pulse-by-Pulse Current Limiting Thermal Shutdown SO-8 Package
MAX5019/MAX5020
Ordering Information
PART MAX5019CSA* MAX5019ESA* MAX5020CSA* MAX5020ESA* TEMP. RANGE +70°C -40°C +85°C +70°C -40°C +85°C PIN-PACKAGE 8-SO 8-SO 8-SO 8-SO
Applications
Telecom Power Supplies Industrial Power Supplies Networking Power Supplies Isolated Power Supplies
*See Selector Guide data sheet.
Typical Operating Circuit Configuration
VOUT
VIEW
MAX5020
NDRV
NDRV
MAX5019/ MAX5020
SS_SHDN
SS_SHDN
8-SO
Maxim Integrated Products
pricing, delivery, ordering information, please contact Maxim/Dallas Direct! 1-888-629-4642, visit Maxim's website www.maxim-ic.com.
Current-Mode Controllers with Integrated Startup Circuit MAX5019/MAX5020
ABSOLUTE MAXIMUM RATINGS
.-0.3V +120V GND.-0.3V +40V GND.-0.3V +12.5V NDRV, SS_SHDN, .-0.3V 0.3V Current .20mA NDRV Current Continuous.25mA NDRV Current Less than 1µs.±1A Continuous Power Dissipation +70°C) 8-Pin (derate 5.88mW/°C above +70°C) .471mW Operating Temperature Range.-40°C +85°C Storage Temperature Range.-65°C +150°C Lead Temperature (soldering, 10s) .+300°C
Stresses beyond those listed under "Absolute Maximum Ratings" cause permanent damage device. These stress ratings only, functional operation device these other conditions beyond those indicated operational sections specifications implied. Exposure absolute maximum rating conditions extended periods affect device reliability.
ELECTRICAL CHARACTERISTICS
(VDD 13V, 10µF capacitor connects GND, 48V, 0.1µF capacitor connected from SS_SHDN GND, NDRV open circuit, -40°C +85°C, unless otherwise noted. Typical values +25°C.)
PARAMETER SUPPLY CURRENT IV+(NS) Supply Current Supply Current After Startup Supply Current Shutdown Current Shutdown Current PREREGULATOR/STARTUP Input Voltage Supply Voltage INTERNAL REGULATORS (VCC) Output Voltage Undervoltage Lockout OUTPUT DRIVER Peak Source Current Peak Sink Current NRDV High-Side Driver Resistance NDRV Low-Side Driver Resistance ERROR AMPLIFIER Input Resistance Input Bias Current Error Amplifier Gain (Inverting) Closed-Loop Bandwidth Input Voltage Range AVCL VSS_SHDN (externally forced) (externally forced) 11V, externally forced, NDRV sourcing 50mA 11V, externally forced, NDRV sinking 50mA 1000 VCC_UVLO Powered from 7.5mA, Powered from VDD, 7.5mA falling 10.0 12.0 11.0 IVDD(NS) IVDD(S) IV+(S) 110V, driver switching 110V, GND, driver switching 110V, 13V, 36V, driver switching 36V, driver switching, VSS_SHDN 110V VSS_SHDN SYMBOL CONDITIONS UNITS
Current-Mode Controllers with Integrated Startup Circuit
ELECTRICAL CHARACTERISTICS (continued)
(VDD 13V, 10µF capacitor connects GND, 48V, 0.1µF capacitor connected from SS_SHDN GND, NDRV open circuit, -40°C +85°C, unless otherwise noted. Typical values +25°C.)
PARAMETER SLOPE COMPENSATION Slope Compensation (MAX5019 only) THERMAL SHUTDOWN Thermal Shutdown Temperature Thermal Hysteresis CURRENT LIMIT Threshold Voltage Input Bias Current Current Limit Comparator Propagation Delay Blanking Time OSCILLATOR Clock Frequency Range Duty Cycle SOFT-START Source Current Sink Current Steady State Reference Voltage SS_SHDN Shutdown Threshold VSS_SHDN external load VSS_SHDN falling VSS_SHDN rising ISSO VSS_SHDN 2.331 0.25 0.53 2.420 0.37 0.59 2.500 0.41 0.65 MAX5019, MAX5020, VILIM 50mV overdrive GND, only comparator blanked VSCOMP mV/µs SYMBOL CONDITIONS UNITS
MAX5019/MAX5020
Typical Operating Characteristics
48V, 13V, GND, NRDV open circuit, +25°C, unless otherwise noted.)
VSS_SHDN TEMPERATURE SOFT-START)
MAX5019 toc01
NDRV FREQUENCY TEMPERATURE
MAX5019 toc02
MAX5019 MAXIMUM DUTY CYCLE TEMPERATURE
MAX5019 toc03
1.003 VSS_SHDN (NORMALIZED VREF 2.4V) 1.002
81.0 80.9 80.8 80.7 80.6 80.5 80.4
1.001
1.000
0.999 TEMPERATURE (°C)
TEMPERATURE (°C)
MAXIMUM DUTY CYCLE
NDRV FREQUENCY (kHz)
TEMPERATURE (°C)
Current-Mode Controllers with Integrated Startup Circuit MAX5019/MAX5020
Typical Operating Characteristics (continued)
48V, 13V, GND, NRDV open circuit, +25°C, unless otherwise noted.)
MAX5020 MAXIMUM DUTY CYCLE TEMPERATURE
MAX5019 toc04
SUPPLY CURRENT TEMPERATURE
MAX5019 toc05
SOFT-START SOURCE CURRENT TEMPERATURE
SOFT-START SOURCE CURRENT (µA) 4.49 4.48 4.47 4.46 4.45 4.44 4.43 4.42 4.41 4.40
MAX5019 toc06
48.0 47.8 47.6 47.4 47.2 47.0 46.8 TEMPERATURE (°C)
1.64 1.63 SUPPLY CURRENT (mA) 1.62 1.61 1.60 1.59 1.58 1.57 1.56 1.55 TEMPERATURE (°C)
4.50 SS_SHDN 110V
MAXIMUM DUTY CYCLE
TEMPERATURE (°C)
INPUT CURRENT TEMPERATURE (AFTER STARTUP)
MAX5019 toc07
SHUTDOWN CURRENT TEMPERATURE
MAX5019 toc08
THRESHOLD VOLTAGE TEMPERATURE
MAX5019 toc09
13.80 13.75 INPUT CURRENT (µA) 13.70 13.65 13.60 13.55 13.50 TEMPERATURE (°C) 110V, 13V,
182.5 SHUTDOWN CURRENT (µA) 182.0 110V, SS_SHDN 181.5 181.0 180.5 180.0 179.5 179.0 TEMPERATURE (°C)
0.488
THRESHOLD VOLTAGE
0.487 0.486
0.485
0.484
0.483 TEMPERATURE (°C)
NDRV RESISTANCE TEMPERATURE
MAX5019 toc10
CURRENT-LIMIT DELAY TEMPERATURE
CURRENT-LIMIT DELAY (ns) 2.400 2.402 GND, 100mV OVERDRIVE VSS_SHDN
MAX5019 toc11
VSS_SHDN
MAX5019 toc12
NDRV RESISTANCE HIGH-SIDE DRIVER TEMPERATURE (°C) LOW-SIDE DRIVER
2.410
2.408
2.406
2.404
TEMPERATURE (°C)
Current-Mode Controllers with Integrated Startup Circuit
Typical Operating Characteristics (continued)
48V, 13V, GND, NRDV open circuit, +25°C, unless otherwise noted.)
MAX5020 MAXIMUM DUTY CYCLE
MAX5019 toc13 MAX5019 toc14
MAX5019/MAX5020
NDRV FREQUENCY
271.0 270.5 NDRV FREQUENCY (kHz) 270.0 269.5 269.0 268.5 268.0 267.5 267.0
47.9 MAXIMUM DUTY CYCLE 47.8 47.7
10.1 10.0
DEVICE POWERED FROM
47.6 47.5 47.4 47.3 47.2 47.1 47.0 DEVICE POWERED FROM DEVICE POWERED FROM
DEVICE POWERED FROM
SUPPLY CURRENT VOLTAGE
1.59 SUPPLY CURRENT (mA) 1.58 1.57 1.56 1.55 1.54 1.53 1.52 1.51 VOLTAGE
MAX5019 toc16
SUPPLY CURRENT VOLTAGE (AFTER STARTUP)
LEAKAGE CURRENT (µA) VOLTAGE 13V,
MAX5019 toc17
1.60
VOLTAGE CURRENT
MAX5019 toc18
VOLTAGE CURRENT
VOLTAGE GND, 110V
MAX5019 toc19
10.4 110V, 10.2 VOLTAGE 10.0 10.0 15.0 CURRENT (mA)
10.0
20.0 10.0 CURRENT (mA) 15.0 20.0
MAX5019 toc15
48.0
10.2
Current-Mode Controllers with Integrated Startup Circuit MAX5019/MAX5020
Description
NAME FUNCTION High-Voltage Startup Input. Connect directly input voltage between 110V. Connects internally high-voltage linear regulator that generates during startup. Input Linear Regulator that Generates VCC. supply voltages less than 36V, both connected supply. supply voltages greater than 36V, receives power from tertiary winding transformer accepts voltages from 36V. Bypass with 4.7µF capacitor. Input Fixed-Gain Inverting Amplifier. Connect voltage-divider from regulated output this pin. noninverting input amplifier referenced 2.4V. Soft-Start Timing Capacitor Connection. Ramp time full current limit approximately 0.45ms/nF. This also reference voltage output. Bypass with minimum 10nF capacitor GND. device goes into shutdown when SS_SHDN pulled below 0.25V. Current Sense Input. Turns power switch rises above 465mV cycle-by-cycle current limiting. also feedback current-mode controller. connected comparator through leading-edge blanking circuit. Ground Gate Drive. Drives high-voltage external N-channel power MOSFET. Regulated Supply. Provides power entire regulated from during normal operation from during startup. Bypass with 10µF tantalum capacitor parallel with 0.1µF ceramic capacitor GND.
SS_SHDN
NDRV
Detailed Description
MAX5019/MAX5020 current-mode controllers design flyback- forward-mode power supplies. Current-mode operation simplifies control-loop design while enhancing loop stability. internal highvoltage startup regulator allows device connect directly input supply without external startup resistor. Current from internal regulator starts controller. Once tertiary winding voltage established internal regulator switched bias current running derived from tertiary winding. internal oscillator 275kHz trimmed ±10%. This permits small magnetic components minimize board space. Both MAX5019 MAX5020 used power supplies providing multiple output voltages. functional diagram shown Figure Typical applications circuits forward flyback topologies shown Figure Figure respectively. isolated flyback power supplies circuit Figure
sensed current signal applied input comparator. current limit comparator monitors times provides cycle-by-cycle current limit without being blanked. leading-edge blanking signal prevents comparator from prematurely terminating cycle. signal contains leading-edge spike that result MOSFET gate charge current, capacitive diode reverse recovery current power circuit. Since this leading-edge spike normally lower than current limit comparator threshold, current limiting blanked cycle-by-cycle current limiting provided under conditions. MAX5019 discontinuous flyback applications where wide line voltage load current variation expected. MAX5020 single transistor forward converters where maximum duty cycle must limited less than 50%. Under certain conditions advantageous forward converter with greater than duty cycle. those cases MAX5019. large duty cycle results much lower operating primary currents through MOSFET switch most cases smaller output filter inductor. major disad-
Current-Mode Control
MAX5019/MAX5020 offer current-mode control operation with added features such leading-edge blanking with dual internal path that only blanks
Current-Mode Controllers with Integrated Startup Circuit MAX5019/MAX5020
VDD-OK HIGHVOLTAGE REGULATOR BIAS WINDING REGULATOR 0.7V
MAX5019 ONLY SLOPE COMPENSATION 26mV/µs 26mV/µs 6.6V
UVLO 275kHz OSCILLATOR NDRV 80%/50% DUTY CYCLE CLAMP ILIM 125mV
ERROR
SS_SHDN 70ns BLANKING
2.4V
0.25V
Figure Functional Diagram
Current-Mode Controllers with Integrated Startup Circuit MAX5019/MAX5020
1N4148 (36V 72V) 4.7µF 10µF SS_SHDN 0.1µF CMHD2003 0.47µF IRF640N SBL204OCT 4.7µH VOUT 5V/10A COUT 560µF 0.1µF
MAX5020
NDRV
RSENSE 100m
(OPTIONAL)
Figure Forward Converter
vantage this that MOSFET voltage rating must higher that slope compensation must provided stabilize inner current loop. MAX5019 provides internal slope compensation.
Internal Regulators
internal regulators MAX5019/MAX5020 enable initial startup without lossy startup resistor regulate voltage output tertiary (bias) winding provide power startup regulated down provide bias device. regulator then regulates from output tertiary winding VCC. This architecture allows tertiary winding only have small filter capacitor output thus eliminating additional cost filter inductor. When designing tertiary winding calculate number turns minimum reflected voltage always higher than 12.7V. maximum reflected voltage must less than 36V. reduce power dissipation high-voltage regulator disabled when voltage reaches 12.7V. This greatly reduces power dissipation improves efficiency. falls below undervoltage lockout threshold (VCC 6.6V), low-voltage regulator dis-
abled, soft-start reinitiated. undervoltage lockout MOSFET driver output (NDRV) held low. input voltage range between 36V, connected line voltage provided that maximum power dissipation exceeded. This eliminates need tertiary winding.
Undervoltage Lockout (UVLO), Soft-Start, Shutdown
soft-start feature MAX5019/MAX5020 allows load voltage ramp controlled manner, thus eliminating output voltage overshoot. While part UVLO, capacitor connected SS_SHDN discharged. Upon coming UVLO internal current source starts charging capacitor initiate soft-start cycle. following equation calculate total soft-start time: tstartup 0.45
where soft-start capacitor shown Figure Operation begins when VSS_SHDN ramps above 0.6V. When soft-start completed, VSS_SHDN regulated
Current-Mode Controllers with Integrated Startup Circuit MAX5019/MAX5020
COUT VOUT
MAX5019 MAX5020
NDRV
SS_SHDN
RSENSE
Figure Nonisolated Flyback Converter
COUT
VOUT
MAX5019 MAX5020
NDRV
RSENSE SS_SHDN
Figure Isolated Flyback Converter
2.4V, internal voltage reference. Pull VSS_SHDN below 0.25V disable controller. Undervoltage lockout shuts down controller when less than 6.6V. regulators reference remain during shutdown.
Current-Sense Comparator
current-sense (CS) comparator associated logic limit peak current through MOSFET. Current sensed voltage across sense resistor between source MOSFET GND. reduce switching noise, connect external MOSFET source through resistor low9
Current-Mode Controllers with Integrated Startup Circuit MAX5019/MAX5020
pass filter (Figures Select current-sense resistor, RSENSE according following equation: RSENSE 0.465V ILimPrimary where ILimPrimary maximum peak primary-side current. When 465mV, power MOSFET switches off. propagation delay from time switch current reaches trip level driver turn-off time 180ns. switch N-channel MOSFET off. normal operation N-channel MOSFET turns when: IPRIMARY RSENSE VREF VSCOMP where IPRIMARY current through N-channel MOSFET, VREF 2.4V internal reference, output voltage internal amplifier, VSCOMP ramp function starting slewing 26mV/µs (MAX5019 only). When using MAX5019 forward-converter configuration following condition must avoid control-loop subharmonic oscillations: RSENSE VOUT 26mV where 0.75 number turns secondary primary side transformer, respectively. output filter inductor. This makes output inductor current downslope referenced across RSENSE equal slope compensation. controller responds transients within cycle when this condition met.
Internal Error Amplifier
MAX5019/MAX5020 include internal error amplifier that used regulate output voltage case nonisolated power supply (see Figure Calculate output voltage using following equation: VOUT VREF where VREF 2.4V. Choose R1//R2 RIN, where RIN, input resistance gain error amplifier internally configured (see Figure error amplifier also used regulate output tertiary winding implementing primaryside regulated isolated power supply (see Figure Calculate output voltage using following equation: VOUT VREF
N-Channel MOSFET Gate Driver
NDRV drives N-channel MOSFET. NDRV sources sinks large transient currents charge discharge MOSFET gate. support such switching transients, bypass with ceramic capacitor. average current result switching MOSFET product total gate charge operating frequency. this current plus quiescent current that determines total operating current.
Applications Information
Design Example
following general procedure designing forward converter using MAX5020. Determine requirements. output voltage. Calculate transformer primary secondary winding turns ratio. Calculate reset primary winding turns ratio. Calculate tertiary primary winding turns ratio. Calculate current-sense resistor value. Calculate output inductor value. Select output capacitor. circuit Figure designed follows:
where number secondary turns number tertiary winding turns.
Comparator Slope Compensation
internal 275kHz oscillator determines switching frequency controller. beginning each cycle, NDRV switches N-channel MOSFET NDRV switches external MOSFET after maximum duty cycle been reached, regardless feedback. MAX5019 uses internal ramp generator slope compensation. internal ramp signal reset beginning each cycle slews 26mV/µs. comparator uses instantaneous current, error voltage, internal reference, slope compensation (MAX5019 only) determine when
Current-Mode Controllers with Integrated Startup Circuit
72V, VOUT IOUT 10A, VRIPPLE 50mV output voltage calculate values resistors according following equation: VOUT VREF VREF VSS_SHDN 2.4V where VREF reference voltage shunt regulator, resistors shown Figures turns ratio transformer calculated based minimum input voltage lower limit maximum duty cycle MAX5020 (44%). enable MOSFETs with drain-source breakdown voltages less than 200V MAX5020 with maximum duty cycle. Calculate turns ratio according following equation: VOUT (VD1 DMAX DMAX VIN_MIN where: NS/NP Turns ratio number secondary turns number primary turns). VOUT Output voltage (5V). Voltage drop across (typically 0.5V power Schottky diodes). DMAX Minimum value maximum operating duty cycle (44%). VIN_MIN Minimum Input voltage (36V). this example: (0.5V 0.44) 0.330 0.44 Choose based core losses resistance. turns ratio calculate rounding nearest integer. this example forward converter choose transformer with magnetizing inductance neighborhood 200µH. Energy stored magnetizing inductance forward converter delivered load must returned back input; this accomplished with reset winding. transformer primary secondary leakage inductance should less than 1µH. Note that leakage energy will dissipated across MOSFET. Snubber circuits used direct some leakage energy dissipated across resistor. calculate minimum duty cycle (DMIN) following equation: VOUT DMIN VIN_MAX where VIN_MAX maximum input voltage (72V). reset winding turns ratio (NR/NP) needs enough guarantee that entire energy transformer returned within cycle maximum duty cycle. following equation determine reset winding turns ratio: where: NR/NP Reset winding turns ratio. DMAX' Maximum value Maximum Duty Cycle. 1-DMAX DMAX
MAX5019/MAX5020
Round nearest smallest integer. turns ratio reset winding will determine peak voltage across N-channel MOSFET. following equation determine maximum drain-source voltage across N-channel MOSFET: VDSMAX VIN_MAX VDSMAX Maximum MOSFET drain-source voltage. VIN_MAX Maximum input voltage.
Current-Mode Controllers with Integrated Startup Circuit MAX5019/MAX5020
VDSMAX 144V Choose MOSFETs with appropriate avalanche power ratings. Choose tertiary winding turns ratio (NT/NP) that minimum input voltage provides minimum operating voltage (13V). following equation calculate tertiary winding turns ratio: VDDMIN VIN_MIN VDDMAX VIN_MAX where: VDDMIN minimum supply voltage (13V). VDDMAX maximum supply voltage (36V). VIN_MIN minimum input supply voltage (36V). VIN_MAX maximum input supply voltage (72V this design example). number turns primary winding. number turns tertiary winding. 13.7 36.7 5.33 7.14 Choose Choose RSENSE according following equation: RSENSE VILIM IOUTMAX Choose inductor value that peak ripple current (LIR) inductor between maximum output current.
275kHz IOUTMAX
(VOUT DMIN
where output Schottky diode forward voltage drop (0.5V).
275kHz
(5.5) 0.198)
4.01µH
size output filter capacitor determine output ripple. Choose capacitor with yield required ripple voltage. following equations calculate peak-topeak output ripple:
VRIPPLE VRIPPLE,ESR VRIPPLE,C
where: VRIPPLE combined output ripple RIPPLE,ESR ripple, RIPPLE,C capacitive ripple. Calculate ripple capacitive ripple follows: VRIPPLE,ESR IRIPPLE VRIPPLE,C IRIPPLE/(2 275kHz COUT)
Layout Recommendations
connections carrying pulsed currents must very short, wide possible, have ground plane return path. inductance these connections must kept minimum high di/dt currents high-frequency switching power converters. Current loops must analyzed layout proposed, internal area kept minimum reduce radiated EMI. Ground planes must kept intact possible.
where: VILim current-sense comparator trip threshold voltage (0.465V). NS/NP secondary side turns ratio (5/14 this example). IOUTMAX maximum output current (10A this example). RSENSE 0.465V 109m
Chip Information
TRANSISTOR COUNT: PROCESS: BiCMOS
Current-Mode Controllers with Integrated Startup Circuit
Table Component Manufacturers
International Rectifier Power FETS Fairchild Vishay-Siliconix Current-Sense Resistors Dale-Vishay Semi Diodes General Semiconductor Central Semiconductor Sanyo Capacitors Taiyo Yuden Coiltronics Magnetics Coilcraft Pulse Engineering www.irf.com www.fairchildsemi.com www.irctt.com/pages/index.cfm www.onsemi.com www.gensemi.com www.centralsemi.com www.sanyo.com www.t-yuden.com www.avxcorp.com www.cooperet.com www.coilcraft.com www.pulseeng.com
MAX5019/MAX5020
Selector Guide
PART MAX5019CSA MAX5019ESA MAX5020CSA MAX5020ESA MAXIMUM DUTY CYCLE SLOPE COMPENSATION
Current-Mode Controllers with Integrated Startup Circuit MAX5019/MAX5020
Package Information
Maxim cannot assume responsibility circuitry other than circuitry entirely embodied Maxim product. circuit patent licenses implied. Maxim reserves right change circuitry specifications without notice time.
_Maxim Integrated Products, Gabriel Drive, Sunnyvale, 94086 408-737-7600 2001 Maxim Integrated Products Printed registered trademark Maxim Integrated Products.
SOICN.EPS
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