19-6179; Rev 0; 1/12 EVALUATION KIT AVAILABLE MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers General Description Benefits and Features The MAX17598/MAX17599 low IQ, active clamp currentmode PWM controllers contain all the control circuitry required for the design of wide-input isolated/non-isolated forward-converter industrial power supplies. The MAX17598 is well-suited for universal input (rectified 85V AC to 265V AC) or telecom (36V DC to 72V DC) power supplies. The MAX17599 is optimized for low-voltage industrial supplies (4.5V DC to 36V DC). S Active Clamp, Peak Current-Mode Forward PWM Controller The devices include an AUX driver that drives an auxiliary MOSFET (clamp switch) that helps implement the active-clamp transformer reset topology for forward converters. Such a reset topology has several advantages including reduced voltage stress on the switches, transformer size reduction due to larger allowable flux swing, and improved efficiency due to elimination of dissipative snubber circuitry. Programmable dead time between the AUX and main driver allows for zero voltage switching (ZVS). S Programmable 100kHz to 1MHz Switching Frequency The switching frequency is programmable from 100kHz to 1MHz for the devices with an accuracy of Q5% using an external resistor. This allows the optimization of the magnetic and filter components, resulting in compact, cost-effective isolated/nonisolated power supplies. For EMI-sensitive design, the ICs incorporate a programmable frequency dithering feature and enables low EMI spread-spectrum operation. An input undervoltage lockout (EN/UVLO) is provided for programming the input-supply start voltage, and to ensure proper operation during brownout conditions. The EN/UVLO input is also used to turn on/off the ICs. Input overvoltage (OVI) protection scheme is provided to make sure that the regulator shuts down when the input supply exceeds its maximum allowed value. To control inrush current, the devices incorporate an SS pin to set the soft-start time for the regulator. Power dissipation under fault conditions is minimized by a hiccup overcurrent protection (hiccup mode). A soft-stop feature provides safe discharging of the clamp capacitor when the device is turned off, and allows the controller to restart in a well-controlled manner. Additionally, a negative current limit is provided in the current-sense circuitry, helping limit the clamp switch current under dynamic operating conditions. A SYNC feature is provided to synchronize multiple converters to a common external clock in noise-sensitive applications. Overtemperature faults trigger a thermal shutdown for reliable protection of the device. The ICs are available in a 16-pin, TQFN package with 0.5 mm lead spacing. S 20FA Startup Current in UVLO S 4.5V to 36V Input-Supply Operating Range (MAX17599) S Programmable Input Undervoltage Lockout S Programmable Input Overvoltage Protection S Switching Frequency Synchronization S Programmable Frequency Dithering for Low EMI Spread-Spectrum Operation S Programmable Dead Time S Adjustable Soft-Start S Programmable Slope Compensation S Fast Cycle-by-Cycle Peak-Current-Limit 40ns Typical Propagation Delay S 70ns Internal Leading-Edge Current-Sense Blanking S Hiccup Mode Output Short-Circuit Protection S Soft-Stop for Well-Controlled Clamp Capacitor Discharge S Negative Current Limit to Limit Clamp-Switch Clamp Capacitor and Transformer Reverse Current S 3mm x 3mm, Lead-Free 16-Pin TQFN Applications Telecom and Datacom Power Supplies Isolated Battery Chargers Servers and Embedded Computing Industrial Power Supplies Ordering Information appears at end of data sheet. For related parts and recommended products to use with this part, refer to www.maxim-ic.com/MAX17598.related. ����������������������������������������������������������������� Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers ABSOLUTE MAXIMUM RATINGS VIN (MAX17599 only).............................................-0.3V to +40V VDRV to SGND (MAX17598 Only)...............................................-0.3V to +16V (MAX17599 Only).................................................-0.3V to +6V EN................................................................-0.3V to (VIN + 0.3V) NDRV, AUXDRV.......................................-0.3V to (VDRV + 0.3V) OVI, RT, DITHER, COMP, SS, FB, SLOPE, DT to SGND...........................................-0.3V to +6V CS to SGND.............................................................-0.8V to +6V PGND to SGND.....................................................-0.3V to +0.3V Maximum Input /Output Current (Continuous) VIN, NDRV, AUXDRV.....................................................100mA NDRV, AUXDRV (pulsed for less than 100ns)...................... ±1A Continuous Power Dissipation (TA = +70NC) TQFN (derate 20.8mW/°C above 70°C).....................1666mW Operating Temperature Range......................... -40°C to +125°C Maximum Junction Temperature......................................+150°C Storage Temperature Range............................. -65°C to +150°C Lead Temperature (soldering, 10s).................................+300°C Soldering Temperature (reflow).......................................+260°C PACKAGE THERMAL CHARACTERISTICS (Note 1) TQFN Junction-to-Case Thermal Resistance (qJC)..................7°C/W Junction-to-Ambient Thermal Resistance (qJA)...........48°C/W Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial. 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 MAX17598, bring VIN up to 21V for startup), VCS = VDITHER = VFB = VOVI = VSGND = VPGND = 0V, VEN = +2V, AUXDRV = NDRV = SS = COMP = SLOPE = unconnected, RRT = 25kI, RDT = 10kI, CVIN = 1FF, CVDRV = 1FF, TA = TJ = -40NC to +125NC, unless otherwise noted. Typical values are at TA = TJ = +25NC.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX MAX17598 8 29 MAX17599 4.5 36 MAX17598 18.5 20 21.5 MAX17599 3.5 4 4.4 MAX17598 6.5 7 7.5 MAX17599 3.3 3.9 4.25 UNITS INPUT SUPPLY (VIN) VIN Voltage Range VIN V VIN Bootstrap UVLO Wakeup VIN-UVR IN rising VIN Bootstrap UVLO Shutdown Level VIN-UVF IN falling VIN Supply Startup Current (under UVLO) IINSTARTUP VIN < UVLO 20 32 FA VEN = 0V 20 32 FA Switching, fSW = 400kHz (MAX17598) 2 Switching, fSW =400kHz (MAX17599) 2 VINC EN = SGND, IIN = 2mA sinking (Note 3) 30 33 36 VENR VEN rising 1.16 1.21 1.26 VENF VEN falling 1.1 1.15 1.20 -100 +100 VIN Supply Shutdown Current IIN-SH VIN Supply Current IIN-SW V V mA VIN CLAMP (INC) (For MAX17598 Only) VIN Clamp Voltage V ENANBLE (EN) EN Threshold EN Input Leakage Current IEN VEN = 1.5V, TA = +25NC V nA ����������������������������������������������������������������� Maxim Integrated Products 2 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers ELECTRICAL CHARACTERISTICS (continued) (VIN = 12V (for MAX17598, bring VIN up to 21V for startup), VCS = VDITHER = VFB = VOVI = VSGND = VPGND = 0V, VEN = +2V, AUXDRV = NDRV = SS = COMP = SLOPE = unconnected, RRT = 25kI, RDT = 10kI, CVIN = 1FF, CVDRV = 1FF, TA = TJ = -40NC to +125NC, unless otherwise noted. Typical values are at TA = TJ = +25NC.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX 7.1 7.4 7.7 UNITS INTERNAL LDO (VDRV) 8V < VIN < 15V and 0mA < IVDRV < 50mA (MAX17598) VDRV Output Voltage Range VVDRV V 6V < VIN < 15V and 0mA < IVDRV < 50mA (MAX17599) 4.7 4.9 5.1 VDRV Current Limit IVDRV-MAX 70 100 mA VDRV Dropout VVDRV-DO VIN = 4.5V, IVDRV = 20mA (MAX17599) 4.2 VOVIR VOVI rising 1.16 1.21 1.26 VOVIF VOVI falling 1.1 1.15 1.2 V OVERVOLTAGE PROTECTION (OVI) OVI Overvoltage Threshold OVI Masking Delay 2 Fs IOVI VOVI = 1V, TA = +25NC -100 +100 nA NDRV Switching Frequency Range fSW 100 1000 kHz NDRV Switching Frequency Accuracy -8 +8 % fSW = 400KHz, RDT = 10kI 71 72.5 74 % 3 V 50 ns OVI Input Leakage Current TOVI-MD V OSCILLATOR (RT) Maximum Duty Cycle DMAX SYNCHRONIZATION (DITHER/SYNC) Synchronization Logic-High Input VIH-SYNC Synchronization Pulse Width Synchronization Frequency Range fSYNCIN 1.1 x fSW DITHERING RAMP GENERATOR (DITHER/SYNC) Charging Current VDITHER = 0V 45 50 55 FA Discharging Current VDITHER = 2.2V 43 50 57 FA Ramp-High Trip Point 2 Ramp-Low Trip Point 0.4 V ����������������������������������������������������������������� Maxim Integrated Products 3 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers ELECTRICAL CHARACTERISTICS (continued) (VIN = 12V (for MAX17598, bring VIN up to 21V for startup), VCS = VDITHER = VFB = VOVI = VSGND = VPGND = 0V, VEN = +2V, AUXDRV = NDRV = SS = COMP = SLOPE = unconnected, RRT = 25kI, RDT = 10kI, CVIN = 1FF, CVDRV = 1FF, TA = TJ = -40NC to +125NC, unless otherwise noted. Typical values are at TA = TJ = +25NC.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS SOFT-START/SOFT-STOP (SS) Soft-Start Charging Current Soft-Stop Discharging Current SS Bias Voltage SS Discharge Threshold ISSCH 9 10 11 FA ISSDISCH 4.4 5 5.6 FA VSS 1.19 1.21 1.23 V V VSSDISCH Soft-stop completion 0.15 Pulldown Impedance RNDRV-N INDRV (sinking) = 100mA 1.37 3 I Pullup Impedance RNDRV-P INDRV (sourcing) = 50mA 4.26 8.5 I Peak Sink Current CNDRV = 10nF 1.5 A Peak Source Current CNDRV = 10nF 0.9 A NDRV DRIVER (NDRV) Fall Time TNDRV-F CNDRV = 1nF 10 ns Rise Time TNDRV-R CNDRV = 1nF 20 ns AUXDRV DRIVER (AUXDRV) Pulldown Impedance RAUXDRV-N IAUXDRV (sinking) = 100mA 3.35 7 I Pullup Impedance RAUXDRV-P IAUXDRV (sourcing) = 50mA 9.78 19 I Peak Sink Current 0.7 A Peak Source Current 0.3 A Fall Time TAUXDRV-F CAUXDRV = 1nF 16 ns Rise Time TAUXDRV-R CAUXDRV = 1nF 32 ns 25 DEAD TIME (DT) NDRV to AUXDRV Delay (Dead Time) NDRV$ to AUXDRV$ TDT AUXDRV# to NDRV# RDT = 10kI 250 RDT = 100kI RDT = 10kI 25 ns 250 RDT = 100kI CURRENT-LIMIT COMPARATOR (CS) Cycle-by-Cycle PeakCurrent-Limit Threshold VCS-PEAK 290 305 320 mV Cycle-by-Cycle RunawayCurrent-Limit Threshold VCS-RUN 340 360 380 mV Cycle-by-Cycle ReverseCurrent-Limit Threshold VCS-REV -122 -102 -82 mV ����������������������������������������������������������������� Maxim Integrated Products 4 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers ELECTRICAL CHARACTERISTICS (continued) (VIN = 12V (for MAX17598, bring VIN up to 21V for startup), VCS = VDITHER = VFB = VOVI = VSGND = VPGND = 0V, VEN = +2V, AUXDRV = NDRV = SS = COMP = SLOPE = unconnected, RRT = 25kI, RDT = 10kI, CVIN = 1FF, CVDRV = 1FF, TA = TJ = -40NC to +125NC, unless otherwise noted. Typical values are at TA = TJ = +25NC.) (Note 2) PARAMETER SYMBOL Current-Sense Leading-Edge Blanking Time tCS-BLANK Current-Sense-Blanking Time for Reverse-Current Limit Propagation Delay from Comparator Input to NDRV tCS-BLANKRev tPDCS CONDITIONS MIN TYP MAX UNITS From NDRV# edge 70 ns From AUXDRV$ edge 70 ns From CS rising (10mV overdrive) to NDRV falling (excluding leading-edge blanking) 40 ns Number of Consecutive Peak-Current-Limit Events to HICCUP NHICCUP-P 8 event Number of Runaway CurrentLimit Events to HICCUP N-HICCUP-R 1 event 90 130 170 ns Overcurrent Hiccup Timeout Minimum On-Time TON-MIN 32,768 cycle SLOPE COMPENSATION (SLOPE) Slope Bias Current ISLOPE 9 10 11 FA Slope Resistor Range RSLOPE 25 200 kI 140 165 190 mV/Fs Slope Compensation Ramp RSLOPE = 100kW Default Slope Compensation Ramp VSLOPE < 0.2V or 4V < VSLOPE 50 mV/Fs PWM COMPARATOR Comparator Offset Voltage VPWM-OS VCOMP - VCS 1.65 1.81 2 V Current-Sense Gain ACS-PWM DCOMP/DCS 1.75 1.97 2.15 V/V CS Peak Slope Ramp Current ICSLOPE Ramp current peak 13 20 FA 110 ns 1.21 1.23 V Comparator Propagation Delay TPWM Change in VCS = 10mV (including internal lead-edge blanking) VREF VFB, when ICOMP = 0V and VCOMP = 1.8V 1.19 IFB VFB = 1.5V, TA = +25NC ERROR AMPLIFIER FB Reference Voltage FB Input Bias Current Open-Loop Voltage Gain Transconductance -100 +100 nA AEAMP 90 dB Gm 1.5 1.8 2.1 mS ����������������������������������������������������������������� Maxim Integrated Products 5 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers ELECTRICAL CHARACTERISTICS (continued) (VIN = 12V (for MAX17598, bring VIN up to 21V for startup), VCS = VDITHER = VFB = VOVI = VSGND = VPGND = 0V, VEN = +2V, AUXDRV = NDRV = SS = COMP = SLOPE = unconnected, RRT = 25kI, RDT = 10kI, CVIN = 1FF, CVDRV = 1FF, TA = TJ = -40NC to +125NC, unless otherwise noted. Typical values are at TA = TJ = +25NC.) (Note 2) PARAMETER Transconductance Bandwidth SYMBOL CONDITIONS MIN TYP MAX UNITS BW Open-loop (gain = 1), -3dB frequency° 10 MHz 80 120 210 FA 80 120 210 FA 160 °C 20 °C Source Current Sink Current VCOMP = 1.8V, VFB = 1V VCOMP = 1.8V, VFB = 1.75V Thermal Shutdown Threshold Temperature rising Thermal Shutdown Hysteresis THERMAL SHUTDOWN Note 2: All devices are 100% production tested at +25NC. Limits over temperature are guaranteed by design. Note 3: The MAX17598 is intended for use in universal input power supplies. The internal clamp circuit at IN is used to prevent the bootstrap capacitor from changing to a voltage beyond the absolute maximum rating of the device when EN is low (shutdown mode). Externally limit the maximum current to IN (hence to clamp) to 2mA (max) when EN is low. Typical Operating Characteristics (VIN = 15V, VEN/UVLO = +2V, COMP = open, CVIN = 1FF, CVCC = 1FF, TA = TJ = -40NC to +125NC, unless otherwise noted.) IN WAKEUP LEVEL vs. TEMPERATURE (MAX17599) 20.02 20.01 20.00 4.05 4.00 3.95 19.99 19.98 3.90 -40 -20 0 20 40 60 TEMPERATURE (°C) 80 100 120 7.025 MAX17598/9 toc03 4.10 IN WAKEUP LEVEL (V) 20.03 MAX17598/9 toc02 4.15 MAX17598/9 toc01 BOOTSTRAP UVLO WAKE-UP LEVEL (V) 20.04 IN UVLO SHUTDOWN LEVEL vs. TEMPERATURE (MAX17598) IN UVLO SHUTDOWN LEVEL (V) BOOTSTRAP UVLO WAKE-UP LEVEL vs. TEMPERATURE (MAX17598) 7.020 7.015 7.010 7.005 7.000 6.995 -40 -20 0 20 40 60 TEMPERATURE (°C) 80 100 120 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) ����������������������������������������������������������������� Maxim Integrated Products 6 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers Typical Operating Characteristics (continued) (VIN = 15V, VEN/UVLO = +2V, COMP = open, CVIN = 1FF, CVCC = 1FF, TA = TJ = -40NC to +125NC, unless otherwise noted.) 3.85 3.80 3.75 23.5 22.5 21.5 20.5 0 20 40 60 80 100 120 0 550 450 350 250 60 0 20 40 60 300 200 5 80 15 25 35 45 65 75 85 95 DEAD TIME vs. RDT MAX17598/9 toc08 12 10 8 6 220 180 140 100 60 20 200 300 400 500 600 700 800 900 1000 100 120 55 FREQUENCY SELECTION RESISTOR (kI) 2 -20 400 80 100 120 4 RT = 100kI 50 10 20 30 40 50 60 70 80 90 100 TEMPERATURE (°C) RDITHER (kI) RDT (kI) DEAD TIME vs. TEMPERATURE PEAK-CURRENT-LIMIT THRESHOLD vs. TEMPERATURE REVERSE CURRENT LIMIT THRESHOLD vs. TEMPERATURE 246 RDT = 100kI 242 305 304 303 302 301 0 20 40 60 TEMPERATURE (°C) 80 100 120 -96 -97 -98 -99 -100 -101 -102 -103 -104 300 -40 -20 MAX17598/9 toc12 306 -95 REVERSE CURRENT LIMIT THRESHOLD (mV) 248 MAX17598/9 toc11 250 307 PEAK-CURRENT-LIMIT THRESHOLD (mV) MAX17598/9 toc10 252 DEAD TIME (ns) 40 DEAD TIME - DT (ns) 650 244 20 14 FREQUENCY DITHERING (%) 750 -40 500 FREQUENCY DITHERING vs. RDITHER MAX17598/9 toc07 NDRV SWITCHING FREQUENCY (kHz) RT = 10kI 150 600 TEMPERATURE (°C) NDRV SWITCHING FREQUENCY vs. TEMPERATURE 850 700 0 -40 -20 TEMPERATURE (°C) 950 800 MAX17598/9 toc09 -20 900 100 19.5 -40 MAX17598/9 toc06 24.5 1000 NDRV SWITCHING FREQUENCY (kHz) 3.90 MAX17598/9 toc05 3.95 25.5 IN SUPPLY CURRENT UNDER UVLO (µA) MAX17598/9 toc04 IN UVLO SHUTDOWN THRESHOLD (V) 4.00 NDRV SWITCHING FREQUENCY vs. RESISTOR IN SUPPLY CURRENT UNDER UVLO vs. TEMPERATURE IN FALLING THRESHOLD vs. TEMPERATURE (MAX17599) -40 -20 0 20 40 60 TEMPERATURE (°C) 80 100 120 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) ����������������������������������������������������������������� Maxim Integrated Products 7 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers Typical Operating Characteristics (continued) (VIN = 15V, VEN/UVLO = +2V, COMP = open, CVIN = 1FF, CVCC = 1FF, TA = TJ = -40NC to +125NC, unless otherwise noted.) FB REGULATION VOLTAGE vs. TEMPERATURE CURRENT-SENSE GAIN vs. TEMPERATURE 1.97 1.96 1.95 1.94 MAX17598/9 toc14 FB REGULATION VOLTAGE (V) 1.98 CURRENT-SENSE GAIN (V/V) 1.217 MAX17598/9 toc13 1.99 1.215 1.213 1.211 1.209 1.207 1.93 1.205 1.92 -40 -20 0 20 40 60 80 -40 100 120 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) TEMPERATURE (°C) ENABLE STARTUP WAVEFORM (DUTY CYCLE SOFT-START) ENABLE SHUTDOWN WAVEFORM (SOFT-STOP) MAX17598/9 toc15 MAX17598/9 toc16 VEN/UVLO 5V/div VEN/UVLO 5V/div VCLAMPCAP 10V/div VCLAMPCAP 10V/div VOUT 5V/div VOUT 5V/div 2ms/div 2ms/div INPUT SHUTDOWN SOFT-START FROM INPUT MAX17598/9 toc17 200ms/div MAX17598/9 toc18 VIN 10V/div VIN 10V/div VOUT 5V/div VOUT 5V/div VCLAMPCAP 25V/div VCLAMPCAP 25V/div 20ms/div ����������������������������������������������������������������� Maxim Integrated Products 8 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers Typical Operating Characteristics (continued) (VIN = 15V, VEN/UVLO = +2V, COMP = open, CVIN = 1FF, CVCC = 1FF, TA = TJ = -40NC to +125NC, unless otherwise noted.) DEAD TIME BETWEEN NDRV AND AUXDRV NDRV AND AUXDRV SIGNALS (TYP APP CIRCUIT) MAX17598/9 toc20 MAX17598/9 toc19 40ns VNDRV 5V/div VNDRV 5V/div VAUXDRV 5V/div VAUXDRV 5V/div 1µs/div 40ns/div NDRV PEAK SOURCE AND SINK CURRENTS AUXDRV PEAK SOURCE AND SINK CURRENTS MAX17598/9 toc21 MAX17598/9 toc22 PEAK SOURCE CURRENT PEAK SOURCE CURRENT IAUXDRV 0.28A/div INDRV 0.7A/div PEAK SINK CURRENT PEAK SINK CURRENT 200ns/div 200ns/div SS, NDRV, AND AUXDRV IN HICCUP MODE MOMENTARY OVI OPERATION MAX17598/9 toc23 MAX17598/9 toc24 VSS 1V/div VOVI 5V/div VNDRV 5V/div VSS 1V/div VOUT 5V/div VAUXDRV 5V/div 4ms/div VCLAMCAP 25V/div 2ms/div ����������������������������������������������������������������� Maxim Integrated Products 9 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers Typical Operating Characteristics (continued) (VIN = 15V, VEN/UVLO = +2V, COMP = open, CVIN = 1FF, CVCC = 1FF, TA = TJ = -40NC to +125NC, unless otherwise noted.) LOAD TRANSIENT RESPONSE (5V OUTPUT) 90 80 VOUT (AC) 100mV/div EFFICIENCY (%) ILOAD 500mA/div VDC = 24V 70 MAX17598/9 toc26 EFFICIENCY GRAPH (5V OUTPUT) MAX17598/9 toc25 60 50 40 30 20 10 0 0 1ms/div 200 400 600 800 1000 1200 1400 LOAD CURRENT (mA) BODE PLOT (5V OUTPUT AND 24V INPUT) ACTIVE CLAMP SWITCHING WAVEFORMS MAX17598/98 toc27 MAX17598/9 toc28 VDS 20V/div PHASE 24°/div BW=19kHz PM = 68° IPRIMARY 0.5A/div GAIN 10dB/div 2 4 6 8 1 2 4 6 8 1 1µs/div ���������������������������������������������������������������� Maxim Integrated Products 10 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers NDRV PGND CS TOP VIEW AUXDRV Pin Configuration 12 11 10 9 VDRV 13 VIN 14 MAX17598 MAX17599 EN/UVLO 15 EP 1 2 3 4 SLOPE RT DITHER/ SYNC + DT OVI 16 TQFN 8 SGND 7 SS 6 FB 5 COMP Pin Description PIN NAME FUNCTION 1 DT Dead-Time Programming Resistor Connection. Connect resistor from DT to GND to set the desired dead time between the NDRV and AUXDRV signals. See the Dead Time section to calculate the resistor value for a particular dead time. 2 SLOPE Slope Compensation Programming Input. A resistor RSLOPE connected from SLOPE to SGND programs the amount of internal slope compensation. Shorting this pin to SGND sets a typical slope compensation of 50mV/Fs. 3 RT Switching Frequency Programming Resistor Connection. Connect resistor from RT to SGND to set the PWM switching frequency. 4 DITHER/SYNC Frequency Dithering Programming or Synchronization Connection. For spread-spectrum frequency operation, connect a capacitor from DITHER to SGND and a resistor from DITHER to RT. To synchronize the internal oscillator to the externally applied frequency, connect DITHER/SYNC to the synchronization pulse. 5 COMP Transconductance Amplifier Output. Connect the frequency compensation network between COMP and SGND. 6 FB Transconductance Error Amplifier Inverting Input 7 SS Soft-Start/Soft-Stop Capacitor Pin for Forward/Flyback Regulator. Connect a capacitor from SS to SGND to set the soft-start/soft-stop time interval. 8 SGND 9 CS 10 PGND Signal Ground. Connect SGND to the signal ground plane. Current-Sense Input. Current-sense connection for average current-sense and cycle-by-cycle current limit. Peak current limit trip voltage is 300mV. Power Ground. Connect PGND to the power ground plane. ���������������������������������������������������������������� Maxim Integrated Products 11 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers Pin Description (continued) PIN NAME FUNCTION 11 NDRV 12 AUXDRV 13 VDRV Linear Regulator Output and Driver Input. Connect a 2.2FF bypass capacitor from VDRV to PGND as close as possible to the IC. 14 VIN Internal VDRV Regulator Input. Connect VIN to the input voltage source. Bypass VIN to PGND with a 1FF minimum ceramic capacitor. 15 EN/UVLO Enable/Undervoltage Lockout Pin. To externally program the UVLO threshold of the input supply, connect a resistive divider among input supply, EN/UVLO, and SGND. 16 OVI Overvoltage Comparator Input. Connect a resistive divider among the input supply, OVI, and SGND to set the input overvoltage threshold. — EP Exposed Pad External Switching NMOS Gate-Driver Output PMOS Active-Clamp-Switch Gate-Driver Output. AUXDRV can also be used to drive a pulse transformer for synchronous flyback application. Detailed Description The MAX17598/MAX17599 low IQ active-clamp currentmode PWM controllers contain all the control circuitry required for the design of wide-input isolated/nonisolated forward converter industrial power supplies. The MAX17598 has a rising UVLO threshold of 20V with a 13V hysteresis, and is therefore well-suited for universal input (rectified 85V AC to 265V AC) or telecom (36V DC to 72V DC) power supplies. The MAX17599 features a 4.1V rising UVLO with a 200mV hysteresis and is optimized for low-voltage industrial supplies (4.5V DC to 36V DC). The devices include an AUX driver that drives an auxiliary MOSFET (clamp switch) that helps implement the activeclamp transformer reset topology for forward converters. Such a reset topology has several advantages, including reduced voltage stress on the switches, transformer size reduction due to larger allowable flux swing, and improved efficiency due to elimination of dissipative snubber circuitry. Programmable dead time between the AUX and main driver allows for zero voltage switching (ZVS). Input Voltage range The MAX17598 has different rising and falling undervoltage lockout (UVLO) thresholds on the VIN pin than those of the MAX17599. The thresholds for the MAX17598 are optimized for implementing power-supply startup schemes typically used for off-line AC/DC and telecom DC-DC power supplies that are typically encountered in electric industrial applications. As such, the MAX17598 has no limitation on the maximum input voltage, as long as the external components are rated suitably, and the maximum operating voltages of the MAX17598 are respected. The MAX17598 can be successfully used in universal input (85V to 265V AC) rectified bus applications, rectified 3-phase DC bus applications, and telecom (36V to 72V DC) applications. The VIN pin of the MAX17599 has a maximum operating voltage of 36V. The MAX17599 implements rising and falling thresholds on the VIN pin that assume powersupply startup schemes, typical of lower voltage DC-DC applications down to an input voltage of 4.5V DC. Thus isolated/non-isolated active-clamp converters with supply-voltage range of 4.5V to 36V can be implemented with the MAX17599. See the Startup Operation section for more details on power-supply startup schemes for the MAX17598/MAX17599. ���������������������������������������������������������������� Maxim Integrated Products 12 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers DT VDRV MAX17598 MAX17599 AUXDRV DRIVER NDRV PGND VDRV 7.5V (MAX17598) OR 5V (MAX17599) THERMAL SENSOR 5V LDO LDO VDRV AUXDRV DEAD TIME PGND AV HICCUP POK VIN NDRV DRIVER CONTROL AND DRIVER LOGIC REVERSE ILIM COMP -100mV UVLO EN/ UVLO CHIPEN SGND OSC OSC 1.21V 8 PEAKEVENTS SSDONE OR 1 RUNAWAY PEAKLIM COMP DITHER (SYNC) OVI PGND 305mV RUNAWAY COMP 1.21V 360mV RT CHIPEN 10µA BLANKING PWM COMP CS 70ns 360mV SS SS 1.21V 5µA FIXED OR VARIABLE SSDONE 10µA SLOPE DECODE SLOPE OSC COMP R 1x CHIPEN/ HICCUP DITHER (SYNC) R 1.21V FB Q50µA SS 2V/0.4V CURRENT SOFT-START Figure 1. Block Diagram ���������������������������������������������������������������� Maxim Integrated Products 13 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers Linear Regulator (VDRV) The MAX17598/MAX17599 have an internal linear converter that is powered from the VIN pin. The output of the linear regulator is connected to the VDRV pin, and should be decoupled with a 2.2FF capacitor to ground for stable operation. The VDRV converter output supplies the MOSFET drivers internally to the MAX17598/MAX17599. The VDRV voltage is regulated at 7.5V (typical) for the MAX17598, and at 5V (typical) for the MAX17599. The maximum operating voltage of the IN pin is 29V for the MAX17598 and 36V for the MAX17599. Maximum Duty Cycle (Dmax) The MAX17598/MAX17599 operate at a maximum duty cycle of 70%. When the SLOPE pin is connected to the VCC pin or left OPEN, it has the necessary amount of slope compensation to provide stable, jitter-free current-mode control operation in applications where the operating duty cycle is less than 50%. Slope compensation is necessary for stable operation of current-mode controlled converters at duty cycles greater than 50%, in addition to the loop compensation required for small signal stability. The MAX17598/MAX17599 implement a SLOPE pin for this purpose. See the Slope Compensation Programming section for more details. Applications Information only if the voltage at the OVI pin falls below 1.15V (typical). The OVI feature is easily disabled by tying the pin to ground. For given values of startup DC input voltage (VSTART) and input overvoltage protection voltage (VOVI), the resistor values for the divider can be calculated as follows, assuming a 24.9kI resistor for ROVI. RSUM represents the series combination of several resistors that might be needed in high-voltage DC bus applications (MAX17598) or a single resistor in low-voltage DC-DC applications (MAX17599). V R EN = 24.9 × OVI − 1 kW, VSTART where VSTART and VOVI are in volts. R SUM= VSTART − 1 kW, 1.21 [24.9 + REN] × where REN is in kI. RSUM might need to be implemented as equal multiple resistors in series (RDC1, RDC2, RDC3) so that voltage across each resistor is limited to its maximum operating voltage. R= DC1 R= DC1 R= DC1 Startup Voltage and Input Overvoltage Protection Setting (EN/UVLO, OVI) The EN/UVLO pin in the MAX17598/MAX17599 serve as an enable/disable input, as well as an accurate programmable undervoltage lockout (UVLO) pin. The MAX17598/ MAX17599 do not commence startup operations unless the EN/UVLO pin voltage exceeds 1.21V (typical). The MAX17598/MAX17599 turn off if the EN/UVLO pin voltage falls below 1.15V (typical). A resistor divider from the input DC bus to ground maybe used to divide down and apply a fraction of the input DC voltage to the EN/UVLO pin as shown in Figure 2. The values of the resistor divider can be selected so that the EN/UVLO pin voltage exceeds the 1.21V (typical) turn on threshold at the desired input DC bus voltage. The same resistor divider can be modified with an additional resistor, ROVI, to implement input overvoltage protection, in addition to the EN/UVLO functionality as shown in Figure 2. When the voltage at the OVI pin exceeds 1.21V (typical), the MAX17598/MAX17599 stop switching. Switching resumes with soft-start operation, R SUM kW. 3 VDC RDC1 RSUM RDC2 RDC3 EN/UVLO REN OVI MAX17598 MAX17599 ROVI Figure 2. Programming EN/UVLO, OVI ���������������������������������������������������������������� Maxim Integrated Products 14 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers Startup Operation The MAX17598 is optimized for implementing activeclamp converters operating either from a rectified AC input or in a 36V DC to 72VDC telecom application. A cost-effective RC startup circuit can be used in such applications. In this startup method (Figure 3), when the input DC voltage is applied, the startup resistor RSTART charges the startup capacitor CSTART, causing the voltage at the VIN pin to increase towards the rising VIN UVLO threshold (20V typical). During this time, the MAX17598 draws a low startup current of 20FA (typical) through the startup resistor RSTART. When the voltage at VIN reaches the rising IN UVLO threshold, the MAX17598 commences switching operations and drives the external MOSFETs connected to NDRV and AUXDRV. In this condition, the MAX17598 draws 2.5mA (typical) current in from CSTART, in addition to the current required to switch the gates of the external MOSFETs Q1and Q2. Since this current cannot be supported by the current through RSTART, the voltage on CSTART starts to drop. When suitably configured as shown in Figure 3, the converter operates to generate an output voltage (VBIAS) that is bootstrapped to the VIN pin. If the voltage VBIAS exceeds 8V before the voltage on CSTART falls below 8V, then the VIN voltage is sustained by VBIAS, thus allowing the MAX17598 to continue to operate with energy from VBIAS. The large hysteresis (13V typical) of the MAX17598 allows for a small startup capacitor (CSTART). The low startup current (20FA typical) allows the use of a large startup resistor (RSTART), thus reducing power dissipation at higher DC bus voltages. The startup resistor RSTART might need to be implemented as equal, multiple resistors in series (RIN1, RIN2 and RIN3) to share the applied high DC voltage in offline applications so that the voltage across each resistor is limited to the maximum continuous operating voltage rating. RSTART and CSTART can be calculated as follows: Q GATE × Fsw TSS C START = µF IIN + × 10 6 10 where IIN is the supply current drawn at the IN pin in mA, QGATE is the sum of the gate charges of the external MOSFETs Q1 and Q2 in nC, fsw is the switching frequency of the converter in Hz, and TSS is the soft-start time programmed for the converter in ms. See the Soft-Start section. = R START (VSTART − 10) × 50 kW, 1 + C START where CSTART is the startup capacitor in FF. The IN UVLO rising threshold of the MAX17599 is set to 4.1V with a hysteresis of 200mV, and is optimized for low-voltage DC-DC applications in the range of 4.5V DC to 36V DC. The IN pin is rated for a maximum operating input voltage of 36V DC and can directly be connected to the input DC supply. VDC RIN1 VDC VBIAS LBIAS D1 RSTART RIN2 D2 RIN3 VIN AUXDRV LDO Q1 MAX17598 NDRV CCLAMP AUXDRV VDRV CVDRV CSTART Q2 Figure 3. RC-Based Startup Circuit ���������������������������������������������������������������� Maxim Integrated Products 15 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers 4.5V TO 36V DC VOUT LOUT D1 VIN MAX17599 LDO D2 AUXDRV Q1 VDRV NDRV COUT CCLAMP AUXDRV CVDRV Q2 Figure 4. Typical Startup Circuit with IN Connected Directly to DC Input Soft-Start and Soft-Stop In a current-mode isolated active clamp forward converter, the COMP voltage programs the peak current in the primary, and thus the secondary-side inductor current as well. The MAX17598/MAX17599 implement a soft-start scheme that controls the COMP pin of the device at turn on. A useful benefit of this feature is the elimination of need for secondary-side soft-start circuitry in such isolated applications. In the absence of secondary-side soft-start circuitry, the secondary-side error amplifier can drive the optocoupler with large currents to cause the output voltage to rapidly reach the regulation value, thus causing inrush current and output voltage overshoot. The MAX17598/MAX17599 avoid this issue by applying a soft-start to the COMP pin. Thus the regulator’s primary and secondary currents are ramped up in a well-controlled manner resulting in a current-mode soft-start operation. The soft-start period of the MAX17598/MAX17599 can be programmed by selecting the value of the capacitor connected from the SS pin to GND. The capacitor CSS can be calculated as follows: T .I V C SS = SS SS COMP VSS 2.6 where ISS = 10FA, VSS = 1.23V, VCOMP is steady-state COMP voltage. A soft-stop feature ramps down the output voltage when the device is turned off, and provides safe discharging of the clamp capacitor, thus allowing the controller to restart in a well-controlled manner. Additionally, a negative current limit is provided in the current-sense circuitry that helps limit the clamp switch current under dynamic operating conditions, such as momentary input overvoltage charging into a precharged output capacitor. The soft-stop duration is twice that of the programmed softstart period. Programming Slope Compensation Since the MAX17598/MAX17599 operate at a maximum duty cycle of 70%, slope compensation is required to prevent subharmonic instability that occurs naturally in continuous mode, peak current mode-controlled converters operating at duty cycles greater than 50%. A minimum amount of slope signal is added to the sensed current signal, even for converters operating below 50% duty to provide stable, jitter-free operation. The SLOPE pin allows the user to program the necessary slope compensation by setting the value of the resistor RSLOPE connected from SLOPE pin to ground. R= SLOPE SE − 8 kW 1.55 where SE, the slope is expressed in mV per microseconds. For the default minimum slope compensation of 50mV/Fs (typical), the SLOPE pin should be connected to SGND or left unconnected. ���������������������������������������������������������������� Maxim Integrated Products 16 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers VSS = ISSCH x t /CSS SOFT-START BEGIN VCOMP - 1.36V SOFT-START ENDS 0.0V 0.4V NDRV AUXDRV CS Figure 5. Duty Cycle Soft-Start SOFT-STOP ENDS VCOMP - 1.36V VSS = 1.23V - ISSDISCH x t/CSS 0.4V SOFT-STOP BEGINS 0.0V NDRV AUXDRV CS Figure 6. Duty Cycle or Current Soft-Stop ���������������������������������������������������������������� Maxim Integrated Products 17 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers n-Channel MOSFET Gate Driver The NDRV output drives an external n-channel MOSFET. NDRV can source/sink in excess of 900mA /1500mA peak current. Therefore, select a MOSFET that yields acceptable conduction and switching losses. p-Channel MOSFET Gate Driver The AUXDRV output drives an external p-channel MOSFET with the aid of a level shifter, as shown in the Typical Application Circuits. AUXDRV can source/sink in excess of 300mA/600mA peak current. Therefore, select a MOSFET that yields acceptable conduction and switching losses. The external PMOSFET used must be able to withstand the maximum clamp voltage. Dead Time Dead time between the main and AUX output edges allow ZVS to occur, minimizing switching losses and improving efficiency. The dead time (tDT) is applied to both leading and trailing edges of the main and AUX outputs as shown in Figure 7. Connect a resistor between DT and GND to set tDT to any value between 25ns and 250ns: = R DT 10kW × (t DT ) 25ns Oscillator/Switching Frequency The ICs’ switching frequency is programmable between 100kHz and 1MHz with a resistor RRT connected between RT and GND. Use the following formula to determine the appropriate value of RRT needed to generate the desired output switching frequency (fSW): R RT = 1× 10 10 fSW where fSW is the desired switching frequency. Peak-Current-Limit The current-sense resistor (RCS), connected between the source of the n-channel MOSFET and PGND, sets the current limit. The source end of the current-sense resistor connects to the CS pin of the MAX17598/MAX17599. The signal thus obtained is used by the devices, both for current-mode control and peak-current limiting purposes. The current-limit comparator has a voltage trip level (VCS-PEAK) of 300mV, and is independent of slope NDRV AUXDRV DEAD TIME, tDT Figure 7. Dead Time Between AUXDRV and NDRV compensation applied to stabilize the converter. The following equation is used to calculate the value of RCS: R CS = 300mV 1.2 × IPRI_PEAK where IPRI_PEAK is the peak current in the primary side of the transformer, which also flows through the main n-channel MOSFET. When the voltage produced by this current (through the current-sense resistor) exceeds the current-limit comparator threshold, the MOSFET driver (NDRV) terminates the current on-cycle within 40ns (typ). The devices implement 70ns of internal leading-edge blanking to ignore leading-edge current spikes encountered in practice due to parasitics. Use a small RC network for additional filtering of the leading-edge spike on the sense waveform when needed. Set the corner frequency of the RC filter network at 5 to 10 times the switching frequency. For a given peak-current-limit setting, the runaway current limit is typically 20% higher. The peak current-limittriggered hiccup operation is disabled until the end of soft-start, while the runaway current-limit-triggered hiccup operation is always enabled. Negative Peak Current Limit The MAX17598/MAX17599 protect against excessive negative currents through the clamp switch, primary of the transformer and the clamp capacitor under dynamic operating conditions where the converter is not in steady state. The devices limit negative current by monitoring the voltage across RCS, while the AUXDRV output is low and the p-Channel FET is on. The typical negative-current-limit threshold is set at -100mV (1/3 of the positivepeak-current-limit threshold). ���������������������������������������������������������������� Maxim Integrated Products 18 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers VCS-PEAK (300mV) CURRENT-SENSE VOLTAGE HICCUP TIMEOUT HICCUP SIGNAL VSS-HI DISCHARGE WITH ISSDISCH SOFT-START VOLTAGE, VSS tSS tRSTR Figure 8. Hiccup-Mode Timing Diagram Output Short-Circuit Protection with Hiccup Mode When the MAX17598/MAX17599 detect eight consecutive peak-current-limit events, both NDRV and AUXDRV driver outputs are turned off (hiccup is followed by soft-stop) for a restart period, tRSTRT. After tRSTRT, the device turns on again with a soft-start. The duration of the restart period is 32678 clock cycles, and therefore depends on the switching frequency setting. The device also features a runaway current limit setting at 120% (typical) of the peak current limit. This feature is useful under short-circuit faults in forward converters with synchronous rectifiers that occur during minimum on-time conditions at high input voltages. Under these conditions, the primary peak current tends to build up and staircase beyond the peak current limit setting due to insufficient discharging of the output inductor. One single event of a runaway current limit forces the MAX17598/MAX17599 into hiccup mode operation. Figure 8 shows the behavior of the device prior and during hiccup mode. Oscillator Synchronization The internal oscillator can be synchronized to an external clock by applying the clock to SYNC/DITHER directly. The external clock frequency can be set anywhere between 1.1x to 1.3x the internal clock frequency. Using an external clock increases the maximum duty cycle by a factor equal to fSYNC /fSW. Frequency Dithering for Spread-Spectrum Applications (Low EMI) The switching frequency of the converter can be dithered in a range of Q10% by connecting a capacitor from DITHER/SYNC to GND, and a resistor from DITHER to RT as shown in the Typical Applications Circuit. This results in lower EMI. ���������������������������������������������������������������� Maxim Integrated Products 19 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers A current source at SYNC/DITHER charges the capacitor CDITHER to 2V at 50FA. Upon reaching this trip point, it discharges CDITHER to 0.4V at 50FA. The charging and discharging of the capacitor generates a triangular waveform on SYNC/DITHER with peak levels at 0.4V and 2V and a frequency that is equal to: fTRI = VOUT COMP RZ RU MAX17598 MAX17599 CP CZ FB 50µA C DITHER × 3.2V Typically, fTRI should be set close to 1kHz. The resistor RDITHER connected from SYNC/DITHER to RT determines the amount of dither as follows: %DITHER = R RT R DITHER where %DITHER is the amount of dither expressed as a percentage of the switching frequency. Setting RDITHER to 10 x RRT generates Q10% dither. Error Amplifier and Loop Compensation The MAX17598/MAX17599 include an internal transconductance-type error amplifier. The noninverting input of the error amplifier is internally connected to the internal reference and the inverting input is brought out at the FB pin to apply the feedback signal. The internal reference is 1.23V (typical) when the device is enabled at turn on. In isolated applications, where an optocoupler is used to transmit the error signal from the secondary side, the emitter current of the optocoupler flows through a resistor to ground to set-up the feedback voltage. A shunt regulator is usually employed as a secondary-side error amplifier to drive the optocoupler photo-diode to couple the error signal to the primary. The loop compensation is usually applied in the secondary side as an R-C network on the shunt regulator. The MAX17598/MAX17599 error amp is set-up as a proportional gain amplifier. This is demonstrated in the Typical Application Circuit for the MAX17598/MAX17599. A useful feature of the MAX17598 is the elimination of need for secondary-side soft-start circuitry. In the absence of secondary side soft-start circuitry, the secondary RB Figure 9. Programming Output Voltage Non-Isolated Applications side error amplifier can drive the optocoupler with large currents to cause the output voltage to rapidly reach the regulation value, thus causing inrush current and output voltage overshoot. The MAX17598/MAX17599 avoid this issue by applying a soft-start to the COMP pin. The regulator’s primary and secondary currents are ramped up in a well-controlled manner, resulting in a current soft-start operation. In nonisolated applications, the output voltage is divided down with a voltage divider to ground and is applied to the FB pin. Loop compensation is applied at the COMP pin as an R-C network from COMP to GND that implements the required poles and zeros, as shown in Figure 9. Active-Clamp Circuit Design The external n-channel and p-channel MOSFETs used must be able to withstand the maximum clamp voltage. For a continuous-mode conduction converter, the clamp voltage is a function of operating duty cycle D and input voltage. The maximum clamp voltage can be obtained as the greater of the results obtained by the following expressions: VCLAMP_max = VIN_max 2 VIN_max − (0.7 × VIN_min ) = 3.33 × VIN_min, VCLAMP_max or where VIN_MAX is the maximum operating DC input voltage, and VIN_MIN is the minimum operating DC input voltage. ���������������������������������������������������������������� Maxim Integrated Products 20 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers The AUX driver controls the p-channel FET through a level shifter. The level shifter consists of an RC network (formed by C8 and R11) and diode D4, as shown in the Typical Applications Circuits. Choose R and C so that the time constant exceeds 100 x fSW. Diode D4 is a smallsignal diode with a voltage rating exceeding 25V. forward- and return-pulsed currents in various parts of the circuit should be minimized. Additionally, small current loop areas reduce radiated EMI. Similarly, the heatsink of the MOSFET presents a dV/dt source. Therefore, the surface area of the MOSFET heatsink should be minimized as much as possible. Additionally, CCLAMP should be chosen so that the complex poles formed by the transformer’s primary magnetizing inductance (LMAG) and CCLAMP are 5x away from the loop bandwidth, and 8x to 10x below the switching frequency of the converter. This allows the clamp capacitor voltage to reach steady-state conditions quickly when subjected to transients in load and line and to avoid transformer saturation. Ground planes must be kept as intact as possible. The ground plane for the power section of the converter should be kept separate from the analog ground plane, except for a connection at the least-noisy section of the power ground plane, typically the return of the input filter capacitor. The negative terminal of the filter capacitor, the ground return of the power switch, and current-sensing resistor must be close together. PCB layout also affects the thermal performance of the design. A number of thermal vias that connect to a large ground plane should be provided under the exposed pad of the part for efficient heat dissipation. For a sample layout that ensures first pass success, please refer to the MAX17598/MAX17599 Evaluation Kit layouts available at www.maxim-ic.com. For universal AC input designs, follow all applicable safety regulations. Offline power supplies can require UL, VDE, and other similar agency approvals. 5 × fBW < 1-D 2π L MAG × C CLAMP < 0.1× fSW Layout Recommendations All connections carrying pulsed currents must be very short and as wide as possible. The inductance of these connections must be kept to an absolute minimum due to the high di/dt of the currents in high-frequency switching power converters. This implies that the loop areas for ���������������������������������������������������������������� Maxim Integrated Products 21 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers Typical Application Circuits L1 1000µH L2 4.7µF D1 VBIAS T1 C5 0.022µF 16V VOUT VOUT D2 R17 0I R18 0I C12 100µF Q1 PGND INPUT 36V TO 72V INPUT C1 22µF C6 0.47µF VBIAS C7 2.2µF 36V PGND U1 C3 68nF SLOPE R5 30kI RT R6 OPEN AUXDRV R11 0I 3.3V, 10A OUTPUT NDRV R12 0I GND0 C11 0.01µF VOUT R20 100I U2 VDRV R23 84kI Q4 R21 OPEN R13 10kI D4 PGND SGND R7 10kI GND Q2 Q3 DITHER/ SYNC R8 6kI VIN PGND C8 0.047µF C4 SHORT VFB VIN SS R4 80kI SGND C14 OPEN R9 10kI C2 0.022µF PGND SGND C13 22µF VFB R19 1.2kI R14 100I MAX17598 CS COMP C9 330pF FB VIN R22 5kI R16 200mI SGND SGND C16 22nF C16 330pF 2 TLV431 3 1 U3 R24 50kI PGND R1 3.1MI EN /UVLO VDRV EN /UVLO C10 2.2µF R2 84kI OVI OVI R3 50kI GND0 VDRV DT R16 20kI PGND EP SGND SGND SGND PGND SGND Figure 10. Typical Application Circuit (Telecom Power Supplies) ���������������������������������������������������������������� Maxim Integrated Products 22 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers Typical Application Circuits (continued) VOUT L2 22µF INPUT VOUT T1 10V TO 30V INPUT C1 22µF 75V R17 0I R10 0I C2 0.1µF 50V R18 0I C11 10µF 16V Q4 C12 10µF 5V, 2A 16V OUTPUT C6 0.47µF PGND GND0 Q3 U1 C3 68nF C10 0.01µF C7 0.01µF AUXDRV SLOPE R5 30kI GND0 VOUT R12 0I R8 10kI VFB 5 VDRV R20 511I U2 1 R23 151.6kI R21 OPEN R13 10kI PGND D4 PGND SGND R9 15kI 6 Q1 DITHER/ SYNC C4 SHORT R11 0I Q2 NDRV RT R6 OPEN SGND PGND SS R4 20kI SGND VIN MAX17599 CS C8 330pF R15 100mI FB SGND VIN VFB R22 5kI 2 R19 1.2kI R14 100I COMP 4 SGND C14 100nF C15 330pF TLV431 2 3 1 U3 R24 50kI PGND VDRV R1 1.14MI EN /UVLO GND0 VDRV C9 2.2µF EN /UVLO R2 109kI OVI OVI R3 50kI SGND DT R16 20kI EP PGND SGND SGND SGND PGND SGND ���������������������������������������������������������������� Maxim Integrated Products 23 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers Ordering Information PART TEMP RANGE PIN PACKAGE MAX17598ATE+ -40NC to +125NC 16 TQFN MAX17599ATE+ -40NC to +125NC 16 TQFN UVLO, IN CLAMP Dmax Active clamp, peak current mode, offline PWM controller 20V, Yes 70% Active clamp, peak current mode, PWM DC-DC controller 4V, No 70% FUNCTIONALITY +Denotes a lead(Pb)-free/RoHS-compliant package. Package Information For the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO. 16L TQFN T1633+4 21-0136 90-0032 ���������������������������������������������������������������� Maxim Integrated Products 24 MAX17598/MAX17599 Low IQ, Wide-Input Range, Active Clamp Current-Mode PWM Controllers Revision History REVISION NUMBER REVISION DATE 0 1/12 DESCRIPTION Initial release PAGES CHANGED — 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. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2012 Maxim Integrated Products 25 Maxim is a registered trademark of Maxim Integrated Products, Inc.