19-3176; Rev 1; 7/04 High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator The MAX5068 is a high-frequency, current-mode, pulse-width modulation (PWM) controller that integrates all the building blocks necessary for implementing ACDC or DC-DC fixed-frequency power supplies. Isolated or nonisolated power supplies are easily constructed using either primary- or secondary-side regulation. Current-mode control with leading-edge blanking simplifies control-loop design, and a programmable internal slope-compensation circuit stabilizes the current loop when operating at duty cycles above 50%. The MAX5068A/B limit the maximum duty cycle to 50% for use in single-ended forward converters. The MAX5068C/D/E/F allow duty cycles up to 75%. The MAX5068 features an accurate externally programmable oscillator that simplifies system design. An input undervoltage lockout (UVLO) programs the input-supply startup voltage and ensures proper operation during brownout conditions. A single external resistor programs the output switching frequency from 12.5kHz to 1.25MHz. The MAX5068A/ B/C/E provide a SYNC input for synchronization to an external clock. The maximum FET-driver duty cycle is 50% for the MAX5068A/B and 75% for the MAX5068C/ D/E/F. Programmable hiccup current limit provides additional protection under severe faults. The MAX5068 is specified over the -40°C to +125°C automotive temperature range and is available in a 16-pin thermally enhanced TSSOP-EP package. Refer to the MAX5069 data sheet for dual FET-driver applications. Warning: The MAX5068 is designed to work with high voltages. Exercise caution. Features ♦ Current-Mode Control with 47µA (typ) Startup Current ♦ Resistor-Programmable ±4.5% Accurate Switching Frequency: 25kHz to 1.25MHz (MAX5068A/B) 12.5kHz to 625kHz (MAX5068C/D/E/F) ♦ Rectified 85VAC to 265VAC or 36VDC to 72VDC Input (MAX5068A/C/D) ♦ Input Directly Driven from 10.8V to 24V (MAX5068B/E/F) ♦ Frequency Synchronization Input (MAX5068A/B/C/E) ♦ Programmable Dead Time and Slope Compensation ♦ Programmable Startup Voltage (UVLO) ♦ Programmable UVLO Hysteresis (MAX5068A/B/D/F) ♦ Integrating Fault Protection (Hiccup) ♦ -40°C to +125°C Automotive Temperature Range ♦ 16-Pin Thermally Enhanced TSSOP-EP Package Ordering Information TEMP RANGE PIN-PACKAGE MAX5068AAUE PART -40°C to +125°C 16 TSSOP-EP* MAX5068BAUE -40°C to +125°C 16 TSSOP-EP* MAX5068CAUE -40°C to +125°C 16 TSSOP-EP* MAX5068DAUE -40°C to +125°C 16 TSSOP-EP* MAX5068EAUE -40°C to +125°C 16 TSSOP-EP* -40°C to +125°C 16 TSSOP-EP* MAX5068FAUE *EP = Exposed pad. Pin Configurations Applications Universal-Input AC Power Supplies Isolated Telecom Power Supplies TOP VIEW RT 1 Networking System Power Supplies SYNC 2 Server Power Supplies HYST 3 Industrial Power Conversion Selector Guide appears at end of data sheet. DT 4 16 REG5 15 IN 14 VCC MAX5068A/B 13 NDRV UVLO/EN 5 12 AGND FB 6 11 PGND COMP 7 10 AGND FLTINT 8 9 CS TSSOP-EP Pin Configurations continued at end of data sheet. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX5068 General Description MAX5068 High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator ABSOLUTE MAXIMUM RATINGS IN to PGND ............................................................-0.3V to +30V IN to AGND.............................................................-0.3V to +30V VCC to PGND..........................................................-0.3V to +13V VCC to AGND..........................................................-0.3V to +13V FB, COMP, CS, HYST, SYNC, REG5 to AGND ........-0.3V to +6V UVLO/EN, RT, DT, SCOMP, FLTINT to AGND .........-0.3V to +6V NDRV to PGND...........................................-0.3V to (VCC + 0.3V) AGND to PGND .....................................................-0.3V to +0.3V Continuous Power Dissipation 16-Pin TSSOP-EP (derate 21.3mW/°C above +70°C) ...1702mW Operating Temperature Range..........................-40°C to +125°C Maximum Junction Temperature .....................................+150°C Storage Temperature Range .............................-60°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VIN = +12V for the MAX5068B/E/F; VIN = +23.6V for the MAX5068A/C/D at startup, then reduces to +12V; CIN = CREG5 = 0.1µF; CVCC = 1µF; RRT = 100kΩ; NDRV = floating; TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS UNDERVOLTAGE LOCKOUT/STARTUP Bootstrap UVLO Wake-Up Level VSUVR VIN rising, MAX5068A/C/D only 19.68 21.6 23.60 V Bootstrap UVLO Shutdown Level VSUVF VIN falling, MAX5068A/C/D only 9.05 9.74 10.43 V UVLO/EN Wake-Up Threshold VULR2 VUVLO/EN rising 1.205 1.230 1.255 UVLO/EN Shutdown Threshold VULF2 VUVLO/EN falling HYST FET On-Resistance RDS(ON)_H V MAX5068A/B/D/F only, sinking 50mA, VUVLO/EN = 0V 10 Ω nA HYST FET Leakage Current ILEAK_H VUVLO/EN = 2V, VHYST = 5V 3 IN Supply Current In Undervoltage Lockout ISTART VIN = +19V, VUVLO/EN < VULF2 47 IN Range V 1.18 VIN 10.8 90 µA 24.0 V 10.5 V 5.15 V INTERNAL SUPPLIES (VCC and REG5) VCC Regulator Set Point VCCSP VIN = +10.8V to +24V, VCC sourcing 1µA to 25mA 7.0 REG5 Output Voltage VREG5 IREG5 = 0 to 1mA 4.85 REG5 Short-Circuit Current Limit IN Supply Current After Startup Shutdown Supply Current IREG5_SC IIN 5.00 18 VIN = +24V fSW = 1.25MHz mA 5 fSW = 100kHz mA 2.5 IIN_SD 90 µA GATE DRIVER (NDRV) Driver Output Impedance Driver Peak Output Current ZOUT(LOW) NDRV sinking 100mA 2 4 ZOUT(HIGH) NDRV sourcing 25mA 3 6 Sinking 1000 Sourcing 650 INDRV Ω mA PWM COMPARATOR Comparator Offset Voltage VOS_PWM VCOMP - VCS Comparator Propagation Delay tPD_PWM VCS = 0.1V 1.30 1.60 40 2.00 ns V Minimum On-Time tON(MIN) Includes tCS_BLANK 110 ns CURRENT-LIMIT COMPARATOR Current-Limit Trip Threshold 2 VCS 298 314 _______________________________________________________________________________________ 330 mV High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator (VIN = +12V for the MAX5068B/E/F; VIN = +23.6V for the MAX5068A/C/D at startup, then reduces to +12V; CIN = CREG5 = 0.1µF; CVCC = 1µF; RRT = 100kΩ; NDRV = floating; TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER CS Input Bias Current CS Blanking Time SYMBOL IB_CS CONDITIONS VCS = 0V MIN 0 tCS_BLANK Propagation Delay from Comparator Input to NDRV TYP 50mV overdrive MAX UNITS +2 µA 70 ns 40 ns IN CLAMP VOLTAGE IN Clamp Voltage VIN_CLAMP VIN sinking 2mA (Note 2) 24.0 26.0 29.0 V Voltage Gain AV RCOMP = 100kΩ to AGND 80 dB Unity-Gain Bandwidth BW RCOMP = 100kΩ to AGND, CLOAD = 100pF to AGND 5 MHz Phase Margin PM RCOMP = 100kΩ to AGND, CLOAD = 100pF to AGND 65 degrees ERROR AMPLIFIER (FB, COMP) FB Input Offset Voltage VOS_FB COMP Clamp Voltage VCOMP Error-Amplifier Output Current ICOMP Reference Voltage VREF Input Bias Current COMP Short-Circuit Current 3 High 2.6 3.8 Low 0.4 1.1 Sinking or sourcing 0.5 mV V mA +25°C ≤ TA ≤ +125°C (Note 3) 1.215 1.230 1.245 -40°C ≤ TA ≤ +125°C 1.205 1.230 1.242 300 V IB_EA 100 ICOMP_SC 12 nA TSD +170 °C THYST +25 °C mA THERMAL SHUTDOWN Thermal-Shutdown Temperature Thermal Hysteresis OSCILLATOR SYNC INPUT (MAX5068A/B/C/E Only) SYNC High-Level Voltage VIH_SYNC SYNC Low-Level Voltage VIL_SYNC SYNC Input Bias Current IB_SYNC Maximum SYNC Frequency fSYNC 2.4 V 0.4 10 fOSC = 2.5MHz (Note 4) V nA 3.125 MHz SYNC High-Level Pulse Width tSYNC_HI 30 ns SYNC Low-Level Pulse Width tSYNC_LO 30 ns DIGITAL SOFT-START Soft-Start Duration tSS Reference-Voltage Step (Note 5) VSTEP Reference-Voltage Steps During Soft-Start 2047 cycles 9.7 mV 127 steps OSCILLATOR Internal Oscillator Frequency Range fOSC fOSC = (1011 / RRT) 50 2500 kHz _______________________________________________________________________________________ 3 MAX5068 ELECTRICAL CHARACTERISTICS (continued) MAX5068 High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator ELECTRICAL CHARACTERISTICS (continued) (VIN = +12V for the MAX5068B/E/F; VIN = +23.6V for the MAX5068A/C/D at startup, then reduces to +12V; CIN = CREG5 = 0.1µF; CVCC = 1µF; RRT = 100kΩ; NDRV = floating; TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 11 NDRV Switching Frequency RT Voltage fSW VRT (Note 6) Oscillator Accuracy TA = -40°C to +125°C DMAX 25 1250 kHz fSW = 1011/(4 x RRT), MAX5068C/D/E/F 12.5 625 kHz fOSC ≤ 500kHz -2.5 40kΩ < RRT < 500kΩ TA = +25°C Maximum Duty Cycle fSW = 10 /(2 x RRT), MAX5068A/B DT connected to REG5 2.0 V +2.5 fOSC > 500kHz -4 +4 fOSC ≤ 500kHz -4.5 +4.5 fOSC > 500kHz -6 +6 MAX5068A/B 50 MAX5068C/D/E/F 75 % % DEAD-TIME CONTROL (DT) Dead Time Dead-Time Disable Voltage Dead-Time Regulation Voltage tDT RDT = 24.9kΩ 60 ns VREG5 - 0.5V VDT_DISABLE VDT V 1.23 V 60 µA INTEGRATING FAULT PROTECTION (FLTINT) FLTINT Source Current FLTINT Shutdown Threshold IFLTINT VFLTINT = 0 VFLTINT_SD VFLTINT rising 2.8 V VFLTINT_RS VFLTINT falling SLOPE COMPENSATION (SCOMP) MAX5068C/D/E/F Only 1.6 V FLTINT Restart Threshold Slope Compensation VSLOPE CSLOPE = 100pF, RRT = 110kΩ 15 mV/µs Slope-Compensation Range VSLOPER 0 90 mV/µs Slope-Compensation Voltage Range VSCOMP 0 2.7 V Note 1: The MAX5068 is 100% tested at TA = +25°C. All limits over temperature are guaranteed by design. Note 2: The MAX5068A/B are intended for use in universal-input power supplies. The internal clamp circuit is used to prevent the bootstrap capacitor (C1 in Figure 1) from charging to a voltage beyond the absolute maximum rating of the device when UVLO/EN is low. The maximum current to VIN (hence to clamp) when UVLO is low (device is in shutdown) must be externally limited to 2mA. Clamp currents higher than 2mA may result in clamp voltages higher than 30V, thus exceeding the absolute maximum rating for VIN. For the MAX5068C/D, do not exceed the 24V maximum operating voltage of the device. Note 3: Reference voltage (VREF) is measured with FB connected to COMP (see the Functional Diagram). Note 4: The SYNC frequency must be at least 25% higher than the programmed oscillator frequency. Note 5: The internal oscillator clock cycle. Note 6: The MAX5068A/B driver switching frequency is one-half of the oscillator frequency. The MAX5068C/D/E/F driver switching frequency is one-quarter of the oscillator frequency. 4 _______________________________________________________________________________________ High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator MAX5068A/C/D 21.5 VIN FALLING MAX5068A/C/D 9.9 9.8 9.7 UVLO/EN RISING 1.240 UVLO/EN (V) VIN (V) VIN (V) 21.4 21.3 1.245 MAX5068 toc02 10.0 MAX5068 toc01 21.6 UVLO/EN WAKE-UP THRESHOLD vs. TEMPERATURE MAX5068 toc03 BOOTSTRAP UVLO SHUTDOWN LEVEL vs. TEMPERATURE BOOTSTRAP UVLO WAKE-UP LEVEL vs. TEMPERATURE 1.235 1.230 21.2 9.6 21.1 1.225 9.5 21.0 10 35 60 85 -15 10 35 60 85 110 -40 -15 10 35 60 85 110 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) UVLO/EN SHUTDOWN THRESHOLD vs. TEMPERATURE VIN SUPPLY CURRENT IN UNDERVOLTAGE LOCKOUT vs. TEMPERATURE VIN SUPPLY CURRENT AFTER STARTUP vs. TEMPERATURE 60 1.18 VIN = 19V WHEN IN BOOTSTRAP UVLO (MAX5068A/C/D) UVLO/EN (MAX5068B/E/F) IS LOW 56 6 MAX5068 toc06 UVLO/EN FALLING 1.19 1.220 -40 110 MAX5068 toc05 1.20 -15 MAX5068 toc04 -40 VIN = 24V fSW = 1.25MHz 5 1.16 1.15 1.14 52 IIN (mA) ISTART (µA) UVLO/EN (V) 1.17 4 48 3 44 2 fSW = 500kHz fSW = 250kHz 1.13 fSW = 100kHz 1.11 40 -15 10 35 60 85 110 10 35 60 85 VCC vs. TEMPERATURE REG5 OUTPUT VOLTAGE vs. OUTPUT CURRENT 9.7 VIN = 19V, IIN = 10mA VIN = 19V, IIN = 25mA 4.980 RRT = 100kΩ 4.975 9.1 110 -40 35 60 85 110 4.99 VIN = 10.8V 100µA LOAD 4.98 4.97 4.965 8.2 7.9 10 REG5 vs. TEMPERATURE 5.00 REG5 (V) 8.5 -15 TEMPERATURE (°C) 4.970 8.8 REG5 (V) VCC (V) -15 TEMPERATURE (°C) 10.0 9.4 -40 TEMPERATURE (°C) MAX5068 toc07 -40 fSW = 50kHz 1 MAX5068 toc08 1.10 MAX5068 toc09 1.12 4.96 1mA LOAD 4.95 4.94 4.960 4.93 VIN = 10.8V, IIN = 10mA 7.6 VIN = 10.8V, IIN = 25mA 7.3 7.0 4.92 4.955 4.91 4.950 -40 -15 10 35 60 TEMPERATURE (°C) 85 110 4.90 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 OUTPUT CURRENT (mA) -40 -15 10 35 60 85 110 TEMPERATURE (°C) _______________________________________________________________________________________ 5 MAX5068 Typical Operating Characteristics (VIN = +12V for the MAX5068B/E/F; VIN = +23.6V for MAX5068A/C/D at startup, then reduces to +12V; CIN = CREG5 = 0.1µF; CVCC = 1µF; RRT = 100kΩ; NDRV = floating; VFB = 0; VCOMP = floating; VCS = 0; TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VIN = +12V for the MAX5068B/E/F; VIN = +23.6V for MAX5068A/C/D at startup, then reduces to +12V; CIN = CREG5 = 0.1µF; CVCC = 1µF; RRT = 100kΩ; NDRV = floating; VFB = 0; VCOMP = floating; VCS = 0; TA = +25°C, unless otherwise noted.) 4.981 4.980 4.979 4.978 318 315 312 309 4.977 306 4.976 303 4.975 10 12 14 16 18 20 22 510 MEAN 505 500 -3σ 495 490 485 480 -15 10 35 60 85 470 -40 110 10 -15 35 60 85 TEMPERATURE (°C) PROPAGATION DELAY FROM CS COMPARATOR INPUT TO NDRV vs. TEMPERATURE INPUT CURRENT vs. INPUT CLAMP VOLTAGE INPUT CLAMP VOLTAGE vs. TEMPERATURE 42 40 38 36 10 8 6 4 34 MAX5068 toc15 26.6 26.4 26.2 26.0 25.8 25.6 25.2 0 -15 10 35 60 85 110 25.0 10.0 12.5 15.0 17.5 20.0 22.5 25.0 27.5 30.0 -40 10 35 60 85 110 INPUT CLAMP VOLTAGE (V) TEMPERATURE (°C) NDRV OUTPUT IMPEDANCE vs. TEMPERATURE NDRV OUTPUT IMPEDANCE vs. TEMPERATURE ERROR AMPLIFIER OPEN-LOOP GAIN AND PHASE vs. FREQUENCY 2.6 3.8 VIN = 24V SOURCING 25mA 3.6 100 80 3.4 RON (Ω) 2.2 2.0 3.2 3.0 1.8 2.8 1.6 2.6 1.4 2.4 1.2 2.2 1.0 GAIN (dB) 2.4 120 2.0 -15 10 35 60 TEMPERATURE (°C) 85 110 MAX5068 toc18 4.0 MAX5068 toc17 VIN = 24V SINKING 100mA -40 -15 TEMPERATURE (°C) MAX5068 toc16 -40 -15 10 35 60 TEMPERATURE (°C) 85 110 0 -30 GAIN -60 60 40 -90 PHASE 20 -120 0 -150 -20 -180 -40 -40 30 -210 0.1 10 1k 100k FREQUENCY (Hz) _______________________________________________________________________________________ 10M PHASE (DEGREES) 30 2.8 ISINK = 2mA 26.8 25.4 2 32 3.0 110 27.0 INPUT CLAMP VOLTAGE (V) 12 INPUT CURRENT (mA) 44 MAX5068 toc14 14 MAX5068 toc13 46 MAX5068 toc12 TOTAL NUMBER OF DEVICES = 200 +3σ TEMPERATURE (°C) 48 6 fSW = 500kHz 475 300 -40 24 515 VIN (V) 50 PROPAGATION DELAY (ns) 324 321 520 SWITCHING FREQUENCY (kHz) 4.982 REG5 (V) 327 CS TRIP THRESHOLD (mV) 4.983 MAX5068 toc11 IREG5 = 100µA 4.984 330 MAX5068 toc10 4.985 SWITCHING FREQUENCY vs. TEMPERATURE CS TRIP THRESHOLD vs. TEMPERATURE REG5 OUTPUT VOLTAGE vs. VIN RON (Ω) MAX5068 High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator 12.0 11.5 62.6 11.0 RON (Ω) 62.7 62.5 10.0 62.3 9.5 62.2 9.0 62.1 8.5 62.0 -15 10 35 60 85 110 0.01 -40 -15 10 35 60 85 110 0.03 0.1 2 1 TEMPERATURE (°C) TEMPERATURE (°C) RRT (MΩ) NDRV SWITCHING FREQUENCY vs. TEMPERATURE NDRV SWITCHING FREQUENCY vs. TEMPERATURE NDRV SWITCHING FREQUENCY vs. TEMPERATURE 50.8 50.4 50.0 49.6 49.2 48.8 fSW = 500kHz 503 502 501 500 499 498 497 1.40 1.35 MAX5068 toc24 504 NDRV SWITCHING FREQUENCY (kHz) 51.2 NDRV SWITCHING FREQUENCY (kHz) fSW = 50kHz MAX5068 toc23 505 MAX5068 toc22 52.0 MAX5068A/B fSW = 1.25MHz 1.30 1.25 1.20 1.15 496 48.4 495 48.0 -15 10 35 60 85 1.10 -50 110 TEMPERATURE (°C) -25 0 25 50 75 TEMPERATURE (°C) 125 100 DEAD TIME vs. TEMPERATURE 65 VIN = 24V RDT = 24.9kΩ RRT = 100kΩ -15 10 35 60 85 110 DEAD TIME vs. RDT 200 MAX5068 toc26 70 -40 TEMPERATURE (°C) MAX5068 toc25 180 160 140 60 TIME (ns) -40 TIME (ns) NDRV SWITCHING FREQUENCY (kHz) 0.1 MAX5068C/D/E/F 8.0 -40 51.6 MAX5068A/B 10.5 62.4 1 fSW (MHz) 62.8 VIN = 24V SINKING 50mA 12.5 2 MAX5068 toc20 62.9 FLTINT CURRENT (µA) 13.0 MAX5068 toc19 63.0 NDRV SWITCHING FREQUENCY (fSW) vs. RRT HYST RON vs. TEMPERATURE MAX5068 toc21 FLTINT CURRENT vs. TEMPERATURE 55 50 120 100 80 60 40 45 20 40 0 -40 -15 10 35 60 TEMPERATURE (°C) 85 110 1 10 100 RDT (kΩ) _______________________________________________________________________________________ 7 MAX5068 Typical Operating Characteristics (continued) (VIN = +12V for the MAX5068B/E/F; VIN = +23.6V for MAX5068A/C/D at startup, then reduces to +12V; CIN = CREG5 = 0.1µF; CVCC = 1µF; RRT = 100kΩ; NDRV = floating; VFB = 0; VCOMP = floating; VCS = 0; TA = +25°C, unless otherwise noted.) MAX5068 High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator Pin Description PIN MAX5068A MAX5068B MAX5068C MAX5068E MAX5068D MAX5068F NAME 1 1 1 RT 2 2 — SYNC External-Clock Sync Input. Connect SYNC to AGND when not using an external clock. 3 — 2 HYST Programmable Hysteresis Input — 3 3 SCOMP 4 4 4 DT 5 5 5 UVLO/EN 6 6 6 FB 7 7 7 COMP Error-Amplifier Compensation Output FLTINT Fault-Integration Input. A capacitor connected to FLTINT charges with an internal 60µA current source during repeated current-limit events. Switching terminates when VFLTINT reaches 2.9V. An external resistor connected in parallel discharges the capacitor. Switching resumes when VFLTINT drops to 1.6V. 8 8 8 8 FUNCTION Oscillator-Timing Resistor Connection. Connect a resistor from RT to AGND to set the internal oscillator frequency. Slope-Compensation Capacitor Input. Connect a capacitor to AGND to set the slope compensation. Dead-Time Adjustment. Connect a resistor from DT to AGND to adjust NDRV dead time. Connect to REG5 for maximum duty cycle. Externally Programmable Undervoltage Lockout. UVLO/EN programs the input start voltage. Drive UVLO/EN to AGND to disable the output. Error-Amplifier Inverting Input 9 9 9 CS 10, 12 10, 12 10, 12 AGND Current-Sense Resistor Connection Analog Ground. Connect to PGND through a ground plane. 11 11 11 PGND Power Ground. Connect to AGND through a ground plane. 13 13 13 NDRV Gate-Driver Output. Connect the NDRV output to the gate of the external N-channel FET. 14 14 14 VCC 15 15 15 IN 16 16 16 REG5 EP EP EP PAD 9V Linear-Regulator Output. Decouple VCC with a minimum 1µF ceramic capacitor to the AGND plane; also internally connected to the FET driver. Power-Supply Input. IN provides power for all internal circuitry. Decouple IN with a minimum 0.1µF ceramic capacitor to AGND (see the Typical Operating Circuit). 5V Linear-Regulator Output. Decouple to AGND with a 0.1µF ceramic capacitor. Exposed Pad. Connect to GND. _______________________________________________________________________________________ High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator The MAX5068 is a current-mode PWM controller for use in isolated and nonisolated power-supply applications. A bootstrap UVLO with a programmable hysteresis, very low startup, and low operating current result in high-efficiency universal-input power supplies. In addition to the internal bootstrap UVLO, the device also offers programmable input startup and turn-off voltages, programmed through the UVLO/EN input. When using the MAX5068 in the bootstrapped mode, if the power-supply output is shorted, the tertiary winding voltage drops below the 10V threshold, causing the bootstrap UVLO to turn off the gate drive to the external power MOSFET, reinitiating a startup sequence with soft-start. The MAX5068 includes a cycle-by-cycle current limit that turns off the gate drive to the external MOSFET during an overcurrent condition. The MAX5068 integrating fault protection reduces average power dissipation during persistent fault conditions (see the Integrating Fault Protection section). The MAX5068 features a very accurate, wide-range, programmable oscillator that simplifies and optimizes the design of the magnetics. The MAX5068A/C/D are well suited for universal-input (rectified 85V AC to 265VAC) or telecom (-36VDC to -72VDC) power supplies. The MAX5068B/E/F are well suited for low-input voltage (10.8VDC to 24VDC) power supplies. The MAX5068 high-frequency, universal input, offline/ telecom, current-mode PWM controller integrates all the building blocks necessary for implementing AC-DC and DC-DC fixed-frequency power supplies. Isolated or nonisolated power supplies are easily constructed using either primary- or secondary-side regulation. Currentmode control with leading-edge blanking simplifies control-loop design, and an external slope-compensation control stabilizes the current loop when operating at duty cycles above 50% (MAX5068C/D/E/F). The MAX5068A/B limit the maximum duty cycle to 50% for use in single-ended forward converters. The MAX5068C/D/E/F allow duty cycles up to 75% for use in flyback converters. An input undervoltage lockout (UVLO) programs the input-supply startup voltage and ensures proper operation during brownout conditions. An external voltagedivider programs the supply startup voltage. The MAX5068A/B/D/F feature a programmable UVLO hysteresis. The MAX5068A/C/D feature an additional internal bootstrap UVLO with large hysteresis that requires a minimum startup voltage of 23.6V. The MAX5068B/E/F start up from a minimum voltage of 10.8V. Internal digital softstart reduces output-voltage overshoot at startup. A single external resistor programs the switching frequency from 12.5kHz to 1.25MHz. The MAX5068A/B/C/E provide a SYNC input for synchronization to an external clock. The maximum FET driver duty cycle is 50% for the MAX5068A/B, and 75% for the MAX5068C/D/E/F. Integrating fault protection ignores transient overcurrent conditions for a set length of time. The length of time is programmed by an external capacitor. The internal thermal-shutdown circuit protects the device if the junction temperature should exceed +170°C. Power supplies designed with the MAX5068 use a high-value startup resistor, R1, which charges a reservoir capacitor, C1 (Figure 1). During this initial period, while the voltage is less than the internal bootstrap UVLO threshold, the device typically consumes only 47µA of quiescent current. This low startup current and the large bootstrap UVLO hysteresis help to minimize the power dissipation across R1, even at the high end of the universal AC input voltage (265VAC). The MAX5068 includes a cycle-by-cycle current limit that turns off the gate to the external MOSFET during an overcurrent condition. When using the MAX5068A/C/D in the bootstrap mode (if the power-supply output is shorted), the tertiary winding voltage drops below the 9.74V bootstrap UVLO to turn off the gate to the external power MOSFET. This reinitiates a startup sequence with soft-start. Current-Mode Control The MAX5068 offers a current-mode control operation feature, such as leading-edge blanking with a dual internal path that only blanks the sensed current signal applied to the input of the PWM controller. The currentlimit comparator monitors CS at all times and provides cycle-by-cycle current limit without being blanked. The leading-edge blanking of the CS signal prevents the PWM comparator from prematurely terminating the on cycle. The CS signal contains a leading-edge spike that results from the MOSFET gate charge current, and the capacitive and diode reverse-recovery current of the power circuit. Since this leading-edge spike is normally lower than the current-limit comparator threshold, current limiting is provided under all conditions. Use the MAX5068C/D/E/F in flyback applications where wide line voltage and load-current variations are expected. Use the MAX5068A/B for forward/flyback converters where the maximum duty must be limited to less than 50%. _______________________________________________________________________________________ 9 MAX5068 Detailed Description MAX5068 High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator D1 VOUT D2 C6 VIN C1 R1 R8 R2 IN NDRV Q1 C2 FLTINT CS VCC FB R9 C3 C4 MAX5068A RCS R5 C5 REG5 COMP R3 R6 RT UVLO/EN R4 RHYST DT SYNC AGND HYST PGND R7 Figure 1. Nonisolated Power Supply with Programmable Input Supply Voltage Use the MAX5068C/D/E/F in forward converter applications with greater than 50% duty cycle. The large duty cycle results in much lower operating primary RMS current through the MOSFET switch and, in most cases, requires a smaller output filter capacitor. The major disadvantage to this is that the MOSFET voltage rating must be higher. The MAX5068C/D/E/F capacitor adjustable-slope-compensation feature allows for easy stabilization of the inner current loop. Undervoltage Lockout The MAX5068 features an input voltage UVLO/EN function to enable the PWM controller before any operation can begin. The MAX5068C/E shut down if the voltage at UVLO/EN falls below its 1.18V threshold. The MAX5068A/B/D/F also incorporate an UVLO hysteresis input to set the desired turn-off voltage. MAX5068C/E UVLO Adjustment The MAX5068C/E have an input voltage UVLO/EN with a 1.231V threshold. Before any operation can commence, the UVLO/EN voltage must exceed the 1.231V threshold. The UVLO circuit keeps the PWM comparator, ILIM comparator, oscillator, and output driver shut down to reduce current consumption (see the Functional Diagram). Calculate R6 in Figure 2 by using the following formula: ⎛ V ⎞ R6 = ⎜ ON − 1⎟ × R7 ⎝ VULR2 ⎠ where VULR2 is the UVLO/EN’s 1.231V rising threshold and VON is the desired startup voltage. Choose an R7 value in the 20kΩ range. After a successful startup, the MAX5068C/E shut down if the voltage at UVLO/EN drops below its 1.18V threshold. 10 ______________________________________________________________________________________ High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator MAX5068 VIN MAX5068C/E R6 UVLO/EN R7 VHYST = VON - VOFF 1.23V 1.18V VOFF Figure 2. Setting the MAX5068C/E Undervoltage Lockout Threshold MAX5068A/B/D/F UVLO with Programmable Hysteresis In addition to programmable undervoltage lockout during startup, the MAX5068A/B/D/F incorporate a UVLO/EN hysteresis that allows the user to set a voltage (VOFF) to disable the controller (see Figure 3). At the beginning of the startup sequence, UVLO/EN is below the 1.23V threshold, Q1 turns on connecting RHYST to GND (Figure 4). Once the UVLO 1.23V threshold is crossed, Q1 turns off, resulting in the series combination of R6, RHYST, and R7, placing the MAX5068 in normal operating condition. Calculate the turn-on voltage (VON) by using the following formula: VON Figure 3. MAX5068 Hysteresis VIN MAX5068A/B/D/F R6 UVLO/EN RHYST 1.23V 1.18V HYST Q1 R7 ⎛ V ⎞ R6 = ⎜ ON − 1⎟ × RHYST ⎝ VULR2 ⎠ where VULR2 is the UVLO/EN’s 1.23V rising threshold. Choose an RHYST value in the 20kΩ range. The MAX5068 turns off when the MAX5068 UVLO/EN falls below the 1.18V falling threshold. The turn-off voltage (VOFF) is then defined as: ⎛ V ⎞ R7 = R6 / ⎜ OFF − 1⎟ − RHYST ⎝ VULF2 ⎠ where VULF2 is the 1.18V UVLO/EN falling threshold. Figure 4. Setting the MAX5068A/B/D/F Turn-On/Turn-Off Voltages Bootstrap Undervoltage Lockout (MAX5068A/C/D Only) In addition to the externally programmable UVLO function offered by the MAX5068, the MAX5068A/C/D feature an additional internal bootstrap UVLO for use in high-voltage power supplies (see the Functional Diagram). This allows the device to bootstrap itself during initial power-up. The MAX5068A/C/D start when VIN exceeds the bootstrap UVLO threshold of 23.6V. ______________________________________________________________________________________ 11 MAX5068 High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator During startup, the UVLO circuit keeps the PWM comparator, ILIM comparator, oscillator, and output driver shut down to reduce current consumption. Once VIN reaches 23.6V, the UVLO circuit turns on both the PWM and ILIM comparators, as well as the oscillator, and allows the output driver to switch. When V IN drops below 9.7V, the UVLO circuit shuts down the PWM comparator, ILIM comparator, oscillator, and output driver returning the MAX5068A/C/D to the startup mode. VCC 2V/div MAX5068 VIN PIN 5V/div MAX5068A/C/D Startup Operation Normally, VIN is derived from the tertiary winding of the transformer. However, at startup there is no energy delivered through the transformer, hence, a special bootstrap sequence is required. Figure 5 shows the voltages on VIN and VCC during startup. Initially, both VIN and VCC are zero. After the input voltage is applied, C1 charges through the startup resistor, R1, to an intermediate voltage (see Figure 1). At this point, the internal regulator begins charging C3 (see Figure 5). Only 47µA of the current supplied by R1 is used by the MAX5068A/C/D. The remaining input current charges C1 and C3. The charging of C3 stops when the VCC voltage reaches approximately 9.5V. The voltage across C1 continues rising until it reaches the wake-up level of 23.6V. Once VIN exceeds the bootstrap UVLO threshold, NDRV begins switching the MOSFET and energy is transferred to the secondary and tertiary outputs. If the voltage on the tertiary output builds to higher than 9.74V (the bootstrap UVLO lower threshold), startup ends and sustained operation commences. If VIN drops below 9.74V before startup is complete, the device goes back to low-current UVLO. If this occurs, increase the value of C1 to store enough energy to allow for the voltage at the tertiary winding to build up. Startup Time Considerations for Power Supplies Using the MAX5068A/C/D The VIN bypass capacitor, C1, supplies current immediately after wakeup (see Figure 1). The size of C1 and the connection configuration of the tertiary winding determine the number of cycles available for startup. Large values of C1 increase the startup time and also supply extra gate charge for more cycles during initial startup. If the value of C1 is too small, VIN drops below 9.74V because NDRV does not have enough time to switch and build up sufficient voltage across the tertiary output that powers the device. The device goes back into UVLO and does not start. Use low-leakage capacitors for C1 and C3. Generally, offline power supplies keep typical startup times to less than 500ms, even in low-line conditions (85VAC input for universal offline applications or 36VDC 12 0V 100ms/div Figure 5. V IN and V CC During Startup When Using the MAX5068 in Bootstrapped Mode (Also see Figure 1) for telecom applications). Size the startup resistor, R1, to supply both the maximum startup bias of the device (90µA) and the charging current for C1 and C3. The bypass capacitor, C3, must charge to 9.5V, and C1 must charge to 24V, within the desired time period of 500ms. Because of the internal soft-start time of the MAX5068, C1 must store enough charge to deliver current to the device for at least 2047 oscillator clock cycles. To calculate the approximate amount of capacitance required, use the following formula: Ig = Qgtot x fSW (IIN + Ig ) x t SS C1 = VHYST where IIN is the MAX5068’s internal supply current after startup (2.5mA typ), Qgtot is the total gate charge for Q1, fSW is the MAX5068’s programmed switching frequency, VHYST is the bootstrap UVLO hysteresis (12V), and tss is the internal soft-start time (2047 x 1 / fOSC). Example: Ig = (8nC) (250kHz) ≅ 2.0mA fOSC = 2 x 250kHz Soft-start duration = 2047 x (1 / fOSC) = 4.1ms C1 = (2.5mA + 2mA) (4.1ms) = 1.54µF 12V Use a 2.2µF ceramic capacitor for C1. ______________________________________________________________________________________ High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator D2 MAX5068 D1 VOUT C7 VIN C1 R1 R2 IN NDRV Q1 C2 FLTINT R11 CS C3 VCC MAX5068A RCS FB C4 R5 REG5 R3 COMP C6 VCC C5 R6 RT C10 R4 UVLO/EN RHYST SYNC AGND R12 PS2913 DT R9 MAX8515 HYST PGND R7 R8 R10 R13 Figure 6. Secondary-Side, Regulated, Isolated Power Supply Assuming C1 > C3, calculate the value of R1 as follows: VSUVR × C1 500ms VIN(MIN) − 0.5 x VSUVR IC1 = R1 ≅ IC1 + ISTART where V SUVR is the bootstrap UVLO wakeup level (23.6V max), VIN(MIN) is the minimum input supply voltage for the application (36V for telecom), and ISTART is the VIN supply current at startup (90µA, max). Oscillator/Switching Frequency For example: 24V x 2.2µF = 106µA 500ms 36V − 12V R1 ≅ = 122.4kΩ 106µA + 90µA IC1 = To minimize power loss on this resistor, choose a higher value for R1 than the one calculated above (if a longer startup time can be tolerated). The above startup method is applicable to a circuit similar to the one shown in Figure 1. In this circuit, the tertiary winding has the same phase as the output windings. Thus, the voltage on the tertiary winding at any given time is proportional to the output voltage and goes through the same soft-start period as the output voltage. The minimum discharge time of C1 from 22V to 10V must be greater than the soft-start time (tSS). Use an external resistor at RT to program the MAX5068 internal oscillator frequency from 50kHz to 2.5MHz. The MAX5068A/B output switching frequency is one-half of the programmed oscillator frequency with a 50% duty cycle. The MAX5068C/D/E/F output switching frequency is one-quarter of the programmed oscillator frequency with a 75% duty cycle. ______________________________________________________________________________________ 13 MAX5068 High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator Use the following formula to calculate the internal oscillator frequency: 1011 fosc = RRT where fOSC is the oscillator frequency and RRT is a resistor connected from RT to AGND. Choose the appropriate resistor at RT to calculate the desired output switching frequency (fSW): RRT = 1011 for the MAX5068A / B and 2fSW RRT = 1011 for the MAX5068C / D / E / F 4fSW The MAX5068A/B and the MAX5068C/D/E/F have programmable output switching frequencies from 25kHz to 1.25MHz and 12.5kHz to 625kHz, respectively. Dead-Time Adjustment The MAX5068 programmable dead-time function (Figure 7) allows additional flexibility in optimizing magnetics design and overcoming parasitic effects. The MAX5068A/B and the MAX5068C/D/E/F have a maximum 50% and 75% duty cycle, respectively. In many applications, the duty cycle of the external MOSFET may need to be slightly decreased to prevent saturation in the transformer’s primary. The dead time can be configured from 30ns to 1 / (0.5 x fSW) when programming the MAX5068. Connect a resistor between DT and AGND to set the desired dead time using the following formula: Dead time = 60 × RDT (ns) 29.4 External Synchronization (MAX5068A/B/C/E) The MAX5068A/B/C/E can be synchronized using an external clock at the SYNC input. For proper frequency synchronization, the SYNC’s input frequency must be at least 25% higher than the MAX5068A/B/C/E programmed internal oscillator frequency. Connect SYNC to AGND when not using an external clock. Integrating Fault Protection The integrating fault-protection feature allows transient overcurrent conditions to be ignored for a programmable amount of time, giving the power supply time to behave like a current source to the load. For example, this can occur under load current transients when the control loop requests maximum current to keep the output voltage from going out of regulation. Program the fault-integration time by connecting an external suitably sized capacitor to the FLTINT. Under sustained overcurrent faults, the voltage across this capacitor ramps up towards the FLTINT shutdown threshold (typically 2.8V). Once the threshold is reached, the power supply shuts down. A high-value bleed resistor connected in parallel with the FLTINT capacitor allows it to discharge towards the restart threshold (typically 1.6V). Once this threshold is reached, the supply restarts with a new soft-start cycle. Note that cycle-by-cycle current limiting is provided at all times by CS with a threshold of 314mV (typ). The fault-integration circuit forces a 60µA current onto FLTINT each time that the current-limit comparator is tripped (see the Functional Diagram). Use the following formula to calculate the value of the capacitor necessary for the desired shutdown time of the circuit: I x tSH CFLTINT ≅ FLTINT 2.8V where RDT is in kΩ and the dead time is in ns. Connect DT to REG5 to remove the delay and achieve the MAX5068 maximum duty cycles. SYNC MAX5068A/B/C/E NDRV RT tDT DEAD TIME < 50% < 50% AGND Figure 7. MAX5068 NDRV Dead-Time Timing Diagram 14 Figure 8. External Synchronization of the MAX5068A/B/C/E ______________________________________________________________________________________ High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator RFLTINT ≅ t RT 0.595 × CFLTINT rent. Therefore, select a MOSFET that yields acceptable conduction and switching losses. Error Amplifier The MAX5068 includes an internal error amplifier that can regulate the output voltage in the case of a nonisolated power supply (Figure 1). Calculate the output voltage using the following equation: R8 ⎞ ⎛ VOUT = ⎜1 + ⎟ x VREF ⎝ R9 ⎠ where tRT is the desired recovery time. Choose tRT = 10 x tSH. Typical values for tSH range from a few hundred microseconds to a few milliseconds. Soft-Start The MAX5068 soft-start feature allows the load voltage to ramp up in a controlled manner, eliminating outputvoltage overshoot. Soft-start begins after UVLO is deasserted. The voltage applied to the noninverting node of the amplifier ramps from 0 to 1.23V in 2047 oscillator clock cycles (soft-start timeout period). Unlike other devices, the MAX5068 reference voltage to the internal amplifier is soft-started. This method results in superior control of the output voltage under heavy- and light-load conditions. Internal Regulators Two internal linear regulators power the MAX5068 internal and external control circuits. VCC powers the external N-channel MOSFET and is internally set to approximately 9.5V. The REG5 5V regulator has a 1mA sourcing capability and may be used to provide power to external circuitry. Bypass VCC and REG5 with 1µF and 0.1µF high quality capacitors, respectively. Use lower value ceramics in parallel to bypass other unwanted noise signals. Bootstrapped operation requires startup through a bleed resistor. Do not excessively load the regulators while the MAX5068 is in the power-up mode. Overloading the outputs can cause the MAX5068 to fail upon startup. N-Channel MOSFET Switch Driver NDRV drives an external N-channel MOSFET. The NDRV output is supplied by the internal regulator (VCC), which is internally set to approximately 9.5V. For the universal input-voltage range, the MOSFET used must be able to withstand the DC level of the high-line input voltage plus the reflected voltage at the primary of the transformer. For most applications that use the discontinuous flyback topology, a MOSFET rated at 600V is required. NDRV can source/sink in excess of 650mA/1000mA peak cur- where VREF = 1.23V. The amplifier’s noninverting input internally connects to a digital soft-start reference voltage. This forces the output voltage to come up in an orderly and well-defined manner under all load conditions. Slope Compensation (MAX5068C/D/E/F) The MAX5068C/D/E/F use an internal-ramp generator for slope compensation. The internal-ramp signal resets at the beginning of each cycle and slews at the rate programmed by the external capacitor connected at SCOMP and the resistor at RT. Adjust the MAX5068 slew rate up to 90mV/µs using the following equation: SR = 165 × 10 −6 (mV / µs) RRT × CSCOMP where RRT is the external resistor at RT that sets the oscillator frequency and CSCOMP is the capacitor at SCOMP. PWM Comparator The PWM comparator uses the instantaneous current, the error amplifier, and the slope compensation to determine when to switch NDRV off. In normal operation, the N-channel MOSFET turns off when: IPRIMARY x RCS > VEA – VOFFSET - VSCOMP where IPRIMARY is the current through the N-channel MOSFET, V EA is the output voltage of the internal amplifier, VOFFSET is the 1.6V internal DC offset and VSCOMP is the ramp function starting at zero and slewing at the programmed slew rate (SR). When using the MAX5068 in a forward-converter configuration, the following conditions must be met to avoid current-loop subharmonic oscillations: K × RCS × VOUT NS × = SR L NP where K = 0.75 and NS and NP are the number of turns on the secondary and primary side of the transformer, respectively. L is the secondary filter inductor. When ______________________________________________________________________________________ 15 MAX5068 where IFLTINT = 60µA, tSH is the desired fault-integration time during which current-limit events from the current-limit comparator are ignored. For example, a 0.1µF capacitor gives a fault-integration time of 4.7ms. This is an approximate formula. Some testing may be required to fine-tune the actual value of the capacitor. To calculate the recovery time, use the following formula: MAX5068 High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator optimally compensated, the current loop responds to input-voltage transients within one cycle. Applications Information Current Limit Keep all PC board traces carrying switching currents as short as possible, and minimize current loops. The current-sense resistor (RCS), connected between the source of the MOSFET and ground, sets the current limit. The CS input has a voltage trip level (V CS) of 314mV. Use the following equation to calculate the value of RCS: RCS = VCS IPRI where IPRI is the peak current in the primary that flows through the MOSFET at full load. When the voltage produced by this current (through the current-sense resistor) exceeds the current-limit comparator threshold, the MOSFET driver (NDRV) quickly terminates the current on-cycle. In most cases, a small RC filter is required to filter out the leading-edge spike on the sense waveform. Set the corner frequency to a few MHz above the switching frequency. 16 Layout Recommendations For universal AC input design, follow all applicable safety regulations. Offline power supplies may require UL, VDE, and other similar agency approvals. Contact these agencies for the latest layout and component rules. Typically, there are two sources of noise emission in a switching power supply: high di/dt loops and high dv/dt surfaces. For example, traces that carry the drain current often form high di/dt loops. Similarly, the heatsink of the MOSFET presents a dv/dt source, thus minimize the surface area of the heatsink as much as possible. To achieve best performance and to avoid ground loops, use a solid ground-plane connection. ______________________________________________________________________________________ High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator D1 VOUT D2 C7 VIN C1 R1 IN R2 NDRV Q1 C2 R11 CS FLTINT C3 RCS VCC MAX5068C C6 FB VCC C4 R5 C5 REG5 COMP R3 R6 C10 RT UVLO/EN R4 R12 PS2913 DT R9 R7 MAX8515 SYNC SCOMP AGND PGND R8 R13 R10 Selector Guide STARTUP VOLTAGE (V) PROGRAMMABLE UVLO HYSTERESIS OSCILLATOR SYNC SLOPE COMPENSATION Yes 23.6 Yes Yes No No 10.8 Yes Yes No 75% Yes 23.6 No Yes Yes 75% Yes 23.6 Yes No Yes MAX5068E 75% No 10.8 No Yes Yes MAX5068F 75% No 10.8 Yes No Yes PART NUMBER MAX DUTY CYCLE BOOTSTRAP UVLO MAX5068A 50% MAX5068B 50% MAX5068C MAX5068D ______________________________________________________________________________________ 17 MAX5068 Typical Operating Circuit High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator MAX5068 Functional Diagram HYST* BOOTSTRAP UVLO MAX5068 UVLO/EN 21.6V/ 9.74V UVLO 1.23V REFERENCE 1.23V/ 1.18V IN VIN CLAMP 26V IN 2.8V/ 1.6V 60µA REGULATOR Q FLTINT REG_OK R 5V OUT REG5 VCC S VCC CURENT-LIMIT COMPARATOR S 314mV 5kΩ + CS + Σ * 1.6V Q NDRV R PGND 70ns BLANKING AGND PWM COMPARATOR OSC DEAD TIME SLOPE COMPENSATION ***SCOMP 1.23V THERMAL SHUTDOWN DIGITAL SOFT-START ERROR AMP FB *MAX5068A/B/D AND MAX5068F ONLY. **MAX5068A/B/C AND MAX5068E ONLY. ***MAX5068C/D/E/F ONLY. 18 COMP SYNC** RT DT ______________________________________________________________________________________ High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator TOP VIEW RT 1 16 REG5 SYNC 2 15 IN 14 VCC SCOMP 3 DT 4 MAX5068C/E RT 1 16 REG5 HYST 2 15 IN 14 VCC SCOMP 3 MAX5068D/F 13 NDRV DT 4 UVLO/EN 5 12 AGND UVLO/EN 5 12 AGND 13 NDRV FB 6 11 PGND FB 6 11 PGND COMP 7 10 AGND COMP 7 10 AGND FLTINT 8 9 FLTINT 8 9 TSSOP-EP CS CS TSSOP-EP Chip Information TRANSISTOR COUNT: 4,266 PROCESS: BiCMOS ______________________________________________________________________________________ 19 MAX5068 Pin Configurations (continued) Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) TSSOP 4.4mm BODY.EPS MAX5068 High-Frequency, Current-Mode PWM Controller with Accurate Programmable Oscillator PACKAGE OUTLINE, TSSOP, 4.40 MM BODY EXPOSED PAD 21-0108 D 1 1 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 20 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.