EVALUATION KIT AVAILABLE MAX17595/MAX17596/ MAX17597 General Description The MAX17595-MAX17597 is a family of peak-currentmode controllers for design of wide input-voltage flyback and boost regulators. The MAX17595 offers optimized input thresholds for universal input AC-DC converters and telecom DC-DC (36V to 72V input range) power supplies. The MAX17596/MAX17597 offer input thresholds suitable for low-voltage DC-DC applications (4.5V to 36V). The MAX17597 implements a boost converter. All three controllers contain a built-in gate driver for external n-channel MOSFETs. The MAX17595-MAX17597 house an internal error amplifier with 1% accurate reference, eliminating the need for an external reference. The switching frequency is programmable from 100kHz to 1MHz with an accuracy of 8%, allowing optimization of magnetic and filter components, resulting in compact and cost-effective power conversion. For EMI-sensitive applications, the MAX17595-MAX17597 family incorporates a programmable frequency dithering scheme, enabling low-EMI spread-spectrum operation. Users can start the power supply precisely at the desired input voltage, implement input overvoltage protection, and program soft-start time. A programmable slope compensation scheme is provided to ensuree stability of the peak-current-mode control scheme. Hiccup-mode overcurrent protection and thermal shutdown are provided to minimize dissipation in overcurrent and overtemperature fault conditions. Applications Universal Input Offline AC-DC Power Supplies Wide-Range DC-Input Flyback/Boost Battery Chargers Battery-Powered Applications Industrial and Telecom Applications 19-6178; Rev 5; 5/17 Peak-Current-Mode Controllers for Flyback and Boost Regulators Benefits and Features Programmable Switching Frequency Allows Optimization of the Magnetic and Filter Components, Resulting in Compact, Cost-Effective, Efficient Isolated/Non-Isolated Power Supplies * 100kHz to 1MHz Programmable Switching Frequency with Optional Synchronization * Peak Current Mode Control Provides Excellent Transient Response -- Offline (Universal Input AC) and Telecom (36V to 72V) Flyback Controller--MAX17595 -- DC-DC (4.5V to 36V) Flyback Controller-- MAX17596 -- Nonsynchronous (4.5V to 36V) Boost PWM Controller--MAX17597 * 3mm x 3mm TQFN Package Programmable Frequency Dithering Enables LowEMI Spread-Spectrum Operation Integrated Protection Features Enhance System Reliability * Adjustable Current Limit with External CurrentSense Resistor * Fast Cycle-By-Cycle Peak Current Limiting * Hiccup-Mode Short-Circuit Protection * Overtemperature Protection * Programmable Soft-Start and Slope Compensation * Input Overvoltage Protection Ordering Information/Selector Guide appears at end of data sheet. MAX17595/MAX17596/ MAX17597 Peak-Current-Mode Controllers for Flyback and Boost Regulators Absolute Maximum Ratings VIN to SGND..........................................................-0.3V to +40V VDRV to SGND................................. -0.3V to +16V (MAX17595) VDRV to SGND......... -0.3V to +6V (MAX17596 and MAX17597) NDRV to SGND..................................... -0.3V to +(VDRV + 0.3)V EN/UVLO to SGND.................................. -0.3V to +(VIN + 0.3)V OVI, RT, DITHER, COMP, SS, FB, SLOPE 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, VDRV..........................................................................100mA NDRV (pulsed, for less than 100ns)........................... 1.5A/-0.9A Continuous Power Dissipation TQFN (single-layer board) (derate 20.8mW/NC above +70NC).............................1666mW Operating Temperature Range.......................... -40NC to +125NC Storage Temperature Range............................. -65NC to +150NC Junction Temperature.......................................................+150NC Lead Temperature (soldering, 10s).................................. +300NC Soldering Temperature (reflow)........................................+260NC 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. Package Thermal Characteristics (Note 1) Junction-to-Ambient Thermal Resistance (qJA)...............48C/W Junction-to-Case Thermal Resistance (qJC)......................7C/W Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial. Electrical Characteristics (VIN = 12V (for the MAX17595, bring VIN up to 21V for startup), VCS = VSLOPE = VDITHER = VFB = VOVI = VSGND = VPGND = 0V, VEN/UVLO = +2V; NDRV, SS, COMP are unconnected, RRT = 25k, CVIN = 1F, CVDRV = 1F, TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = TJ = +25C.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS INPUT SUPPLY (VIN) VIN Voltage Range VIN MAX17595 MAX17596/MAX17597 8 29 4.5 36 MAX17595 18.5 20 21.5 MAX17596/MAX17597 3.8 4.1 4.4 MAX17595 6.5 7 7.5 MAX17596/MAX17597 3.6 3.9 4.2 VIN < UVLO 20 32 FA 32 FA VIN Bootstrap UVLO Wakeup VIN-UVR VIN rising # VIN Bootstrap UVLO Shutdown Level VIN-UVF VIN falling $ VIN Supply Startup Current (Under UVLO) IVINSTARTUP VIN Supply Shutdown Current IIN-SH VEN = 0V 20 VIN Supply Current IIN-SW Switching, fSW = 400kHz 2 VIN Clamp Voltage V VINC MAX17595, IVIN = 2mA sinking, VEN = 0V (Note 3) VENR VENF V V mA 30 33 36 VEN rising # 1.16 1.21 1.26 VEN falling $ 1.1 1.15 1.2 V ENABLE (EN) EN Undervoltage Threshold EN Input Leakage Current www.maximintegrated.com IEN VEN = 1.5V, TA = +25NC -100 +100 V nA Maxim Integrated 2 MAX17595/MAX17596/ MAX17597 Peak-Current-Mode Controllers for Flyback and Boost Regulators Electrical Characteristics (continued) (VIN = 12V (for the MAX17595, bring VIN up to 21V for startup), VCS = VSLOPE = VDITHER = VFB = VOVI = VSGND = VPGND = 0V, VEN/UVLO = +2V; NDRV, SS, COMP are unconnected, RRT = 25k, CVIN = 1F, CVDRV = 1F, TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = TJ = +25C.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX 8V < VIN < 15V and 0mA < IVDRV < 50mA (MAX17595) 7.1 7.4 7.7 6V < VIN < 15V and 0mA < IVDRV < 50mA (MAX17596/MAX17597) 4.7 4.9 5.1 70 100 UNITS INTERNAL LDO (VDRV) VDRV Output Voltage Range VDRV VDRV Current Limit IVDRV-MAX VDRV Dropout VVDRV-DO V mA VIN = 4.5V, IVDRV = 20mA (MAX17596/ MAX17597) 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 OVI Input Leakage Current tOVI-MD IOVI 2 VOVI = 1V, TA = +25NC V Fs -100 +100 nA 100 1000 kHz -8 +8 % OSCILLATOR (RT) NDRV Switching Frequency Range fSW NDRV Switching Frequency Accuracy Maximum Duty Cycle DMAX fSW = 400kHz (MAX17595/MAX17596) 46 48 50 (MAX17597) 90 92.5 95 % SYNCHRONIZATION (DITHER/SYNC) Synchronization Logic-High Input VHI-SYNC 3 Synchronization Pulse Width Synchronization Frequency Range V 50 fSYNC (MAX17595/MAX17596) (Note 4) 1.1 x fSW ns 1.8 x fSW Hz DITHERING RAMP GENERATOR (DITHER/SYNC) Charging Current 45 50 55 FA Discharging Current 43 50 57 FA Ramp-High Trip Point 2 V Ramp-Low Trip Point 0.4 V www.maximintegrated.com Maxim Integrated 3 MAX17595/MAX17596/ MAX17597 Peak-Current-Mode Controllers for Flyback and Boost Regulators Electrical Characteristics (continued) (VIN = 12V (for the MAX17595, bring VIN up to 21V for startup), VCS = VSLOPE = VDITHER = VFB = VOVI = VSGND = VPGND = 0V, VEN/UVLO = +2V; NDRV, SS, COMP are unconnected, RRT = 25k, CVIN = 1F, CVDRV = 1F, TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = TJ = +25C.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 9 10 11 FA 1.21 1.23 V SOFT-START (SS) Soft-Start Charging Current SS Bias Voltage ISSCH VSS 1.19 NDRV DRIVER (NDRV) Pulldown Impedance RNDRV-N INDRV (sinking) = 100mA 1.37 3 I Pullup Impedance RNDRV-P INDRV (sourcing) = 50mA 4.26 8.5 I CNDRV = 10nF 1.5 Peak Sink Current Peak Source Current A CNDRV = 10nF 0.9 A Fall Time tNDRV-F CNDRV = 1nF 10 ns Rise Time tNDRV-R CNDRV = 1nF 20 ns CURRENT-LIMIT COMPARATOR (CS) Cycle-by-Cycle Peak Current-Limit Threshold VCS-PEAK 290 305 320 mV Cycle-by-Cycle Runaway Current-Limit Threshold VCS-RUN 340 360 380 mV Current-Sense LeadingEdge Blanking Time tCS-BLANK From NDRV rising # edge 70 ns From CS rising (10mV overdrive) to NDRV falling (excluding leading edge blanking) 40 ns Propagation Delay from Comparator Input to NDRV tPDCS Number of Consecutive Peak- Current-Limit Events to Hiccup NHICCUP-P 8 events Number of RunawayCurrent-Limit Events to Hiccup NHICCUP-R 1 event 32,768 cycle Overcurrent Hiccup Timeout Minimum On-Time tON-MIN 90 130 170 ns 9 10 11 FA 200 kI SLOPE COMPENSATION (SLOPE) Slope Bias Current Slope Resistor Range www.maximintegrated.com ISLOPE 25 Maxim Integrated 4 MAX17595/MAX17596/ MAX17597 Peak-Current-Mode Controllers for Flyback and Boost Regulators Electrical Characteristics (continued) (VIN = 12V (for the MAX17595, bring VIN up to 21V for startup), VCS = VSLOPE = VDITHER = VFB = VOVI = VSGND = VPGND = 0V, VEN/UVLO = +2V; NDRV, SS, COMP are unconnected, RRT = 25k, CVIN = 1F, CVDRV = 1F, TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = TJ = +25C.) (Note 2) PARAMETER SYMBOL CONDITIONS Slope Voltage Range for Default Slope Compensation MIN TYP MAX 4 Slope Voltage Range for Programmable Slope Compensation V 0.2 Slope Compensation Ramp RSLOPE = 100kW Default Slope Compensation Ramp 4V < VSLOPE 140 UNITS 165 2 V 190 mV/Fs 50 mV/Fs PWM COMPARATOR Comparator Offset Voltage VPWM-OS VCOMP, when VCS = 0 1.65 1.81 2 V Current-Sense Gain ACS-PWM DVCOMP/DVCS 1.75 1.97 2.15 V/V Comparator Propagation Delay tPWM Change in VCS = 10mV (including internal leadedge blanking) FB Reference Voltage VREF VFB, when ICOMP = 0 and VCOMP = 1.8V 1.19 FB Input Bias Current IFB VFB = 1.5V, TA = +25NC -100 110 ns ERROR AMPLIFIER Voltage Gain AEAMP Transconductance Gm Transconductance Bandwidth BW 1.21 1.23 V +100 nA 90 1.5 Open-loop (gain = 1), -3dB frequency dB 1.8 2.1 10 mS MHz Source Current VCOMP = 1.8V, VFB = 1V 80 120 210 FA Sink Current VCOMP = 1.8V, VFB = 1.75V 80 120 210 FA THERMAL SHUTDOWN Thermal-Shutdown Threshold Thermal-Shutdown Hysteresis Temperature rising +160 NC 20 NC Note 2: All devices 100% production tested at TA = +25C. Limits over temperature are guaranteed by design. Note 3: The MAX17595 is intended for use in universal input power supplies. The internal clamp circuit at VIN is used to prevent the bootstrap capacitor from charging to a voltage beyond the absolute maximum rating of the device when EN is low (shutdown mode). Externally limit the maximum current to VIN (hence to clamp) to 2mA (max) when EN is low. Note 4: Using an external clock for synchronization increases the maximum duty cycle by a factor equal to fSYNC / fSW for the MAX17595/MAX17596. External synchronization is not available for the MAX17597. www.maximintegrated.com Maxim Integrated 5 MAX17595/MAX17596/ MAX17597 Peak-Current-Mode Controllers for Flyback and Boost Regulators Typical Operating Characteristics (VIN = 15V, VEN/UVLO = +2V, COMP = open, CVIN = 1F, CVDRV = 1F, TA = TJ = -40C to +125C, unless otherwise noted.) MAX17595/6/7 toc02 4.12 20.03 20.02 20.01 20.00 4.11 4.10 4.09 4.08 19.99 19.98 VIN WAKE-UP LEVEL vs. TEMPERATURE (MAX17596/MAX17597) -40 -20 0 20 40 60 80 4.07 100 120 -40 -20 0 20 40 60 80 100 120 MAX17595/6/7 toc04 1.209 EN /UVLO RISING THRESHOLD (V) VIN UVLO SHUTDOWN THRESHOLD (V) 3.92 3.91 3.90 3.89 3.88 0 20 40 60 7.020 7.015 7.010 7.005 7.000 6.995 80 -40 -20 0 20 40 60 80 TEMPERATURE (C) www.maximintegrated.com 100 120 40 60 80 100 120 MAX17595/6/7 toc05 1.207 1.206 1.205 1.204 1.203 -40 -20 0 20 40 60 80 100 120 OVI RISING THRESHOLD vs. TEMPERATURE MAX17595/6/7 toc07 1.211 OVI RISING THRESHOLD (V) EN /UVLO FALLING THRESHOLD (V) MAX17595/6/7 toc06 1.146 20 TEMPERATURE (C) EN/UVLO FALLING THRESHOLD vs. TEMPERATURE 1.147 0 1.208 1.202 100 120 1.148 1.145 -40 -20 EN/ UVLO RISING THRESHOLD vs. TEMPERATURE TEMPERATURE (C) 1.149 MAX17595/6/7 toc03 7.025 TEMPERATURE (C) VIN FALLING THRESHOLD vs. TEMPERATURE (MAX17596/MAX17597) -40 -20 VIN FALLING THRESHOLD vs. TEMPERATURE (MAX17595) TEMPERATURE (C) TEMPERATURE (C) 3.97 VIN BOOTSTRAP UVLO SHUTDOWN LEVEL (V) 4.13 MAX17595/6/7 toc01 VIN WAKE-UP LEVEL (V) BOOTSTRAP UVLO WAKE-UP LEVEL (V) 20.04 BOOTSTRAP UVLO WAKE-UP LEVEL vs. TEMPERATURE (MAX17595) 1.210 1.209 1.208 1.207 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C) Maxim Integrated 6 MAX17595/MAX17596/ MAX17597 Peak-Current-Mode Controllers for Flyback and Boost Regulators Typical Operating Characteristics (continued) (VIN = 15V, VEN/UVLO = +2V, COMP = open, CVIN = 1F, CVDRV = 1F, TA = TJ = -40C to +125C, unless otherwise noted.) MAX17595/6/7 toc08 VIN SUPPLY CURRENT UNDER UVLO (A) OVI FALLING THRESHOLD (V) 1.1505 1.1500 1.1495 1.1490 1.1485 1.1480 1.1475 -40 -20 0 20 40 60 80 100 120 VIN SUPPLY CURRENT UNDER UVLO vs. TEMPERATURE MAX17595/6/7 toc09 25.5 23.5 22.5 21.5 20.5 -40 -20 40 60 80 600 500 400 300 200 100 15 25 35 45 55 2.1 2.0 1.9 1.8 1.7 1.5 100 120 -40 -20 65 75 85 95 FREQUENCY DITHERING vs. RDITHER MAX17595/6/7 toc13 0 20 40 60 80 100 120 TEMPERATURE (C) NDRV SWITCHING FREQUENCY vs. TEMPERATURE MAX17595/6/7 toc12 NDRV SWITCHING FREQUENCY (kHz) NDRV SWITCHING FREQUENCY (kHz) 700 FREQUENCY SELECTION RESISTOR (kI) FREQUENCY DITHERING (%) 20 MAX17595/6/7 toc11 800 14 0 NDRV SWITCHING FREQUENCY vs. RESISTOR 5 2.2 TEMPERATURE (C) 900 0 2.3 1.6 TEMPERATURE (C) 1000 MAX17595/6/7 toc10 2.4 24.5 19.5 SWITCHING CURRENT vs. TEMPERATURE 2.5 SWITCHING CURRENT (mA) OVI FALLING THRESHOLD vs. TEMPERATURE 950 RRT = 10k 850 750 650 550 450 350 250 RRT = 100k 150 50 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C) SWITCHING WAVEFORMS (MAX17595) MAX17595/6/7 toc14 12 10 VDRAIN 100V/div 8 6 IPRI 1A/div 4 2 200 300 400 500 600 700 800 900 1000 4s/div RDITHER (k) www.maximintegrated.com Maxim Integrated 7 MAX17595/MAX17596/ MAX17597 Peak-Current-Mode Controllers for Flyback and Boost Regulators Typical Operating Characteristics (continued) (VIN = 15V, VEN/UVLO = +2V, COMP = open, CVIN = 1F, CVDRV = 1F, TA = TJ = -40C to +125C, unless otherwise noted.) ENABLE STARTUP ENABLE SHUTDOWN MAX17595/6/7 toc15 HICCUP OPERATION MAX17595/6/7 toc16 EN/UVLO 5V/div MAX17595/6/7 toc17 EN/UVLO 5V/div VOUT 10V/div VOUT 10V/div VOUT 10V/div COMP 1V/div VDRAIN 100V/div COMP 1V/div 2ms /div IPRI 2A/div 1ms/div 400s/div LOAD TRANSIENT RESPONSE (FIGURE 9 OUTPUT) SWITCHING CURRENT vs. SWITCHING FREQUENCY MAX17595/6/7 toc18 MAX17595/6/7 toc19 SWITCHING CURRENT (mA) 2.5 VOUT (AC) 0.5V/div 2.3 2.1 ILOAD 0.5A/div 1.9 1.7 1.5 100 200 300 400 500 600 700 800 900 1000 0.4ms/div SWITCHING FREQUENCY (Hz) EFFICIENCY GRAPH (FIGURE 9 OUTPUT) BODE PLOT (FIGURE 9 OUTPUT) MAX17595/6/7 toc20 MAX17595/6/7 toc21 100 90 PHASE 36/div GAIN 10dB/div BANDWIDTH = 11.5kHz PHASE MARGIN = 50.9 6 81 2 4 6 8 1 2 4 EFFICIENCY (%) 80 VDC = 120V 70 60 50 40 30 20 10 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 LOAD CURRENT (A) www.maximintegrated.com Maxim Integrated 8 MAX17595/MAX17596/ MAX17597 Peak-Current-Mode Controllers for Flyback and Boost Regulators NDRV PGND CS N.C. NDRV PGND CS 12 11 10 9 12 11 10 9 EP 2 3 RT TQFN SS VIN 14 6 FB EN / UVLO 15 5 COMP OVI 16 4 DITHER / SYNC 1 SLOPE + N.C. OVI 16 7 VDRV 13 MAX17597 EP + 1 2 3 4 DITHER EN / UVLO 15 SGND RT MAX17595 MAX17596 VIN 14 8 SLOPE VDRV 13 N.C. TOP VIEW N.C. Pin Configuration TQFN 8 SGND 7 SS 6 FB 5 COMP Pin Description PIN NAME 1, 12 N.C. 2 SLOPE 3 RT Switching Frequency Programming Resistor Connection. Connect resistor RRT 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 (MAX17595/MAX17596 only), connect DITHER/SYNC to the synchronization pulse. 5 COMP Transconductance Amplifier Output. Connect the frequency compensation network between COMP and SGND. 6 FB Transconductance Amplifier Inverting Input 7 SS Soft-Start Capacitor Pin for Flyback Regulator. Connect a capacitor CSS from SS to SGND to set the soft-start time interval. 8 SGND 9 CS 10 PGND Power Ground. Connect PGND to the power ground plane. 11 NDRV External Switching nMOS Gate-Driver Output www.maximintegrated.com FUNCTION No Connection Slope Compensation Input. A resistor, RSLOPE, connected from SLOPE to SGND programs the amount of slope compensation with reference-voltage soft-start mode. Floating the SLOPE pin enables reference voltage soft-start with default slope compensation of 50mV/s. Signal Ground. Connect SGND to the signal ground plane. Current-Sense Input. Peak-current-limit trip voltage is 300mV (typ). Maxim Integrated 9 MAX17595/MAX17596/ MAX17597 Peak-Current-Mode Controllers for Flyback and Boost Regulators Pin Description (continued) PIN NAME FUNCTION 13 VDRV Linear Regulator Output and Driver Input. Connect a 1F bypass capacitor from VDRV to SGND 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 16 OVI Overvoltage Comparator Input. Connect a resistive divider between the input supply, OVI, and SGND to set the input overvoltage threshold. -- EP Exposed Pad. Connect to a large ground plane through multiple vias to maximize thermal dissipation. Enable/Undervoltage Lockout. To externally program the UVLO threshold of the input supply, connect a resistive divider between input supply, EN, and SGND. Detailed Description The MAX17595 offers a bootstrap UVLO wake-up level of 20V with a wide hysteresis, and is optimized for implementing isolated and nonisolated universal (85V to 265V AC) offline single-switch flyback converter or telecom (36V to 72V) power supplies. The MAX17596/MAX17597 offer a UVLO wake-up level of 4.4V and are well-suited for low-voltage DC-DC flyback/boost power supplies. An internal 1% reference (1.21V) can be used to regulate the output in nonisolated flyback and boost applications. Additional semiregulated outputs, if needed, can be generated by using additional secondary windings on the flyback converter transformer. The MAX17595/MAX17596/MAX17597 family utilizes peak-current-mode control and external compensation for optimizing closed-loop performance. The devices include cycle-by-cycle peak current limit, and eight consecutive occurrences of current-limit-event trigger hiccup mode, which protects external components by halting switching for a period of 32,768 cycles. . Input Voltage Range (VIN) The MAX17595 has no limitation on maximum input voltage, as long as the external components are rated suitably and the maximum operating voltages of the MAX17595 are respected. www.maximintegrated.com The MAX17595 implements a rising and falling UVLO threshold that allows it to be successfully used in universal input (85V to 265V AC) rectified bus applications, in rectified 3-phase DC bus applications, and in telecom (36V to 72V DC) applications. The MAX17596/MAX17597 are intended to implement flyback (isolated and nonisolated) and boost converters. The VIN pin of the MAX17596/MAX17597 has a maximum operating voltage of 36V. The MAX17596/ MAX17597 implement rising and falling thresholds on the VIN pin that assume power-supply startup schemes typical of low-voltage DC-DC applications, down to an input voltage of 4.5V DC. Therefore, flyback /boost converters with a 4.5V to 36V supply voltage range can be implemented with the MAX17596/MAX17597. Internal Linear Regulator (VDRV) The internal functions and driver circuits are designed to operate from 7.4V (MAX17595) or 5V (MAX17596/ MAX17597) power-supply voltages. The MAX17595/ MAX17596/MAX17597 family has an internal linear regulator 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 1FF capacitor to ground for stable operation. The VDRV regulator output supplies all the operating current of the MAX17595/MAX17596/MAX17597. The maximum operating voltage on the VIN pin is 29V for the MAX17595, and 36V for the MAX17596/MAX17597. Maxim Integrated 10 MAX17595/MAX17596/ MAX17597 VDRV 7.4V (MAX17595) OR 5V (MAX17596/ MAX17597) 7.4V LDO Peak-Current-Mode Controllers for Flyback and Boost Regulators THERMAL SENSOR MAX17595 MAX17596 MAX17597* 5V LDO CONTROL AND DRIVER LOGIC POK 50A DITHER/SYNC 2V/0.4V HICCUP VDRV VIN NDRV DRIVER UVLO 8 PEAK EVENTS OR 1 RUNAWAY CHIPEN OSC EN / UVLO PGND PEAKLIM COMP PGND 305mV DITHER/ SYNC 1.21V SSDONE OSC RUNAWAY COMP OVI 360mV 1.21V 0.9V BLANKING 70ns PWM COMP RT 10A SS CS FIXED OR VAR 10A CHIPPEN SLOPE SLOPE DECODE SS SSDONE 1.21V OSC R COMP 1X R SGND INTERNAL REFERENCE 1.21V SS FB Figure 1. MAX17595/MAX17596/MAX17597 Block Diagram (*See Note 4.) www.maximintegrated.com Maxim Integrated 11 MAX17595/MAX17596/ MAX17597 n-Channel MOSFET Gate Driver (NDRV) The devices offer a built-in gate driver for driving an external n-channel MOSFET. The NDRV pin can source/sink peak currents in excess of 900mA /1500mA. Maximum Duty Cycle The MAX17595/MAX17596 operate at a maximum duty cycle of 49%. The MAX17597 offers a maximum duty cycle of 94% to implement flyback and boost converters involving large input-to-output voltage ratios in DC-DC applications. Slope compensation is necessary for stable operation of peak-current-mode controlled converters such as the MAX17595/MAX17596 /MAX17597, in addition to the loop compensation required for small signal stability. The MAX17595/MAX17596/MAX17597 implement a SLOPE pin for this purpose. See the Slope Compensation section for more details. Soft-Start (SS) The devices implement soft-start operation for the flyback/ boost regulators. A capacitor connected to the SS pin programs the soft-start period. The soft-start feature reduces input inrush current during startup. When the voltage on the SLOPE pin is more than 0.2V, the reference to the internal error amplifier is ramped up from 0V to 1.21V in a linear manner, as programmed by the soft-start capacitor. See the Programming Soft-Start (SS) section. Peak-Current-Mode Controllers for Flyback and Boost Regulators Applications Information Startup Voltage and Input Overvoltage Protection Setting (EN/UVLO, OVI) The devices' EN/UVLO pin serves as an enable/disable input, as well as an accurate programmable input UVLO pin. The devices do not commence startup operation unless the EN/UVLO pin voltage exceeds 1.21V (typ). The devices turn off if the EN/UVLO pin voltage falls below 1.15V (typ). A resistor-divider from the input DC bus to ground can be used to divide down and apply a fraction of the input DC voltage (VDC) to the EN/UVLO pin. The values of the resistor-divider can be selected so the EN/UVLO pin voltage exceeds the 1.23V (typ) turnon 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 voltage at the OVI pin exceeds 1.21V (typ), the devices stop switching and resume switching operations only if voltage at the OVI pin falls below 1.15V (typ). 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 fol lows, assuming a 24.9kI resistor for ROVI: VOVI R EN = R OVI x - 1 k I V START Switching Frequency Selection (RT) The ICs' switching frequency is programmable between 100kHz and 1MHz with resistor RRT connected between RT and SGND. Use the following formula to determine the appropriate value of RRT needed to generate the desired output-switching frequency (fSW): R RT = 10 10 fSW where fSW is the desired switching frequency. 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 SGND, and a resistor from DITHER to RT. Spread-spectrum modulation technique spreads the energy of switching frequency and its harmonics over a wider band while reducing their peaks, helping to meet stringent EMI goals. www.maximintegrated.com where ROVI is in kI, while VSTART and VOVI are in volts. VSTART R SUM = R OVI + R EN x - 1 k I 1.21 where REN and ROVI are in kI, while VSTART is in volts. In universal AC input applications, RSUM may need to be implemented as equal resistors in series (RDC1, RDC2, and RDC) so that voltage across each resistor is limited to its maximum operation voltage. R = DC1 R= DC2 R= DC3 R SUM 3 kI For low-voltage DC-DC applications based on the MAX17596/MAX17597, a single resistor can be used in the place of RSUM, as the voltage across it is approximately 40V. Maxim Integrated 12 MAX17595/MAX17596/ MAX17597 Peak-Current-Mode Controllers for Flyback and Boost Regulators Startup Operation The MAX17595 is optimized for implementing an offline single-switch flyback converter and has a 20V VIN UVLO wake-up level with hysteresis of 15V (min). In offline applications, a simple cost-effective RC startup circuit is used. 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 wake-up VIN UVLO threshold (20V typ). During this time, the MAX17595 draws a low startup current of 20FA (typ) through RSTART. When the voltage at VIN reaches the wake-up VIN UVLO threshold, the MAX17595 commences switching and control operations. In this condition, the MAX17595 draws 2mA (typ) current from CSTART for its internal operation. In addition, the gate-drive current is also drawn from CSTART, which is a function of the gate charge of the external MOSFET used and switching frequency. Since this total 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 external MOSFET is switched by the NDRV pin and the flyback converter generates pulses on bias winding NB. The soft-start period of the converter should be programmed so the bias winding pulses sustain the voltage on CSTART before it falls below 7V, thus allowing continued operation. The large hysteresis of the MAX17595 allows for a small startup capacitor (CSTART). The low startup current (20FA typ) allows the use of a large startup resistor (RSTART), thus reducing power dissipation at higher DC bus voltages. 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 its maximum continuous operating voltage rating. RSTART and CSTART can be calculated as: C START C VDRV + IIN x t SS x 0.1 0.75 t SS x Q G x fSW F + 0.04 x 10 6 where IIN is the supply current drawn at the VIN pin in mA, QG is the gate charge of the external MOSFET used in nC, fSW is the switching frequency of the converter in Hz, and tSS is the soft-start time programmed for the flyback converter in ms. CVDRV is a cummulative capacitor used in VDRV node in F. See the Programming Soft-Start of Flyback/Boost Converter (SS) section. www.maximintegrated.com RDC1 RSUM RDC2 RDC3 EN/UVLO REN OVI MAX17595 MAX17596 MAX17597 ROVI Figure 2. Programming EN /UVLO and OVI R START = (VSTART - 10) x 50 1 + C START kI where CSTART is the startup capacitor in FF. For designs that cannot accept power dissipation in the startup resistors at high DC input voltages in offline appli cations, the startup circuit can be set up with a current source instead of a startup resistor as shown in Figure 4. The startup capacitor (CSTART) can be calculated using the above equation: Resistors RSUM and RISRC can be calculated as: = R SUM = RISRC VSTART 10 VBEQ1 70 MW MW The VIN UVLO wake-up threshold of the MAX17596/ MAX17597 is set to 4.1V (typ) with a 200mV hysteresis, optimized for low-voltage DC-DC applications down to 4.5V. For applications where the input DC voltage is low enough (e.g., 4.5V to 5.5V DC) that the power loss incurred to supply the operating current of the MAX17596/ MAX17597 can be tolerated, the VIN pin is directly connected to the DC input, as shown in Figure 5. In the case of higher DC input voltages (e.g., 16V to 32V DC), a startup circuit, such as that shown in Figure 6, can be used to minimize power dissipation. In this startup Maxim Integrated 13 MAX17595/MAX17596/ MAX17597 Peak-Current-Mode Controllers for Flyback and Boost Regulators scheme, the transistor (Q1) supplies the switching current until a bias winding NB comes up and turns off Q1. The resistor (RZ) can be calculated as: from the SS pin to SGND. Capacitor CSS can be calculated as: = C SS 8.2645 x t SS nF RZ = 2 x (VINMIN - 6.3) kW where tSS is expressed in ms. This equation is directly applicable to the boost converter application circuit of Figure 11. For optoisolated converters, the soft-start period is approximately equal to 30% of tSS when the Programming Soft-Start (SS) The soft-start period for the devices can be programmed by selecting the value of the capacitor CSS connected VDC VOUT VDC D2 D1 RIN1 RSTART RIN2 MAX17595 RIN3 VIN CSTART NDRV LDO COUT NB DRV NP NS CS VDRV CVDRV Figure 3. MAX17595 RC-Based Startup Circuit VDC RIN1 RSUM RIN2 VDC D2 VOUT D1 RIN3 NB MAX17595 RISRC VIN CSTART COUT NP NS NDRV LDO DRV CS VDRV CVDRV RS Figure 4. MAX17595 Current-Source-Based Startup Circuit www.maximintegrated.com Maxim Integrated 14 MAX17595/MAX17596/ MAX17597 Peak-Current-Mode Controllers for Flyback and Boost Regulators error amplifier is set up as a proportional gain amplifier as shown in Figure 9. selected in the 20kI to 50kI range, RU can be calculated as: Programming Output Voltage VOUT R U =x RB - 1 kI, where R B is in kI. 1.21 The devices incorporate an error amplifier with a 1% precision voltage reference that enables negative feedback control of the output voltage. The output voltage of the switching converter can be programmed by selecting the values for the resistor-divider connected from VOUT, and the flyback /boost output to ground, with the midpoint of the divider connected to the FB pin (Figure 7). With RB Peak-Current-Limit Setting (CS) The devices include a robust overcurrent protection scheme that protects the device under overload and short-circuit conditions. A current-sense resistor, connected between the source of the MOSFET and PGND, sets the peak current limit. The current-limit comparator has a voltage VDC VOUT D1 VIN VIN VDRV LDO COUT CDRV Np Ns NDRV DRV CS MAX17596 MAX17597 RS Figure 5. MAX17596/MAX17597 Typical Startup Circuit with VIN Connected Directly to DC Input VDC D2 D1 RZ Q1 VIN LDO VDRV ZD1 6.3V NB COUT CDRV Np Ns VIN CIN DRV NDRV CS MAX17596 MAX17597 RS Figure 6. MAX17596/MAX17597 Typical Startup Circuit with Bias Winding to Turn Off Q1 and Reduce Power Dissipation www.maximintegrated.com Maxim Integrated 15 MAX17595/MAX17596/ MAX17597 Peak-Current-Mode Controllers for Flyback and Boost Regulators trip level (VCS-PEAK) of 300mV. Use the following equation to calculate the value of RCS: R CS = 300mV IMOSFET I where IMOSFET is the peak current flowing through the MOSFET. The devices implement 65ns of leading-edge blanking to ignore leading-edge current spikes. Use a small RC network for additional filtering of the leading edge spike on the sense waveform when needed. Set the corner frequency between 10MHz and 20MHz. After the leading-edge blanking time, the device monitors VCS. The switching cycle is terminated within 30ns from VCS exceeding 300mV. The devices offer a runaway current limit scheme that protects the devices under high-input-voltage shortcircuit conditions when there is insufficient output voltage available to restore inductor current built up during the on period of the flyback/boost converter. Either eight consecutive occurrences of the peak-current-limit event or one occurrence of the runaway current limit trigger a hiccup mode that protects the converter by immediately suspending switching for a period of time (tRSTART). This allows the overload current to decay due to power loss in the converter resistances, load, and the output diode of the flyback /boost converter before soft-start is attempted again. The runaway current limit is set at a VCS-PEAK of 360mV (typ). The peak-current-limittriggered hiccup operation is disabled until the end of the soft-start period, while the runaway current-limittriggered hiccup operation is always enabled. Programming Slope Compensation (SLOPE) The MAX17595/MAX17596 operate at a maximum duty cycle of 49%. In theory, they do not require slope compensation to prevent subharmonic instability that occurs naturally in continuous-conduction mode (CCM) peak-current-mode-controlled converters operating at duty cycles greater than 50%. In practice, the MAX17595/ MAX17596 require a minimum amount of slope compensation to provide stable operation. The devices allow the user to program this default value of slope compensation simply by leaving the SLOPE pin unconnected. It is recommended that discontinuous-mode designs also use this minimum amount of slope compensation to provide better noise immunity and jitter-free operation. VOUT RU FB RB Figure 7. Programming Output Voltage The MAX17597 flyback /boost converter can be designed to operate in either discontinuous-conduction mode (DCM) or to enter into continuous-conduction mode at a specific load condition for a given DC input voltage. In continuous-conduction mode, the flyback/ boost converter needs slope compensation to avoid subharmonic instability that occurs naturally over all specified load and line conditions in peak-current-modecontrolled 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 the SLOPE pin to ground. R SLOPE = SE - 8 1.55 kI where the slope (SE) is expressed in mV/Fs. 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 SGND, and a resistor from DITHER to RT as shown in the Typical Operating Circuits. This results in lower EMI. A current source at DITHER/SYNC charges 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 DITHER/SYNC with peak levels at 0.4V and 2V and a frequency that is equal to: fTRI = www.maximintegrated.com MAX17595 MAX17596 MAX17597 50 FA C DITHER x 3.2V Maxim Integrated 16 MAX17595/MAX17596/ MAX17597 typically, fTRI should be set close to 1kHz. Resistor RDITHER connected from DITHER/SYNC 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. Synchronization (SYNC) The internal oscillator can be synchronized to an external clock by applying the clock to the DITHER/SYNC pin directly. The external clock frequency can be set anywhere between 1.1x and 1.8x times the programmable switching frequency for the MAX17595/MAX17596. The synchronization feature is not available in the MAX17597. An external clock increases the maximum duty cycle by a factor of (fSYNC / fSW). Error Amplifier and Loop Compensation The MAX17595/MAX17596/MAX17597 include an internal transconductance 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 linearly ramped up from 0V to 1.21V (typ) when the device is enabled at turn-on. After soft-start, the internal reference is connected to the bandgap. In isolated applications, where an optocoupler is used to transmit the control 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 photodiode to couple the control signal to the primary. The loop compensation is applied in the secondary side as an R-C network on the shunt regulator. The MAX17595/MAX17596/MAX17597 error amp can be set up as a proportional gain amplifier, or used to implement additional poles or zeros. The Typical Application Circuits for the MAX17595/MAX17596 use the internal error amplifier as a proportional gain amplifier. 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 www.maximintegrated.com Peak-Current-Mode Controllers for Flyback and Boost Regulators the required poles and zeros, as shown in Figure 8. The boost converter application circuit of Figure 11 for the MAX17597 uses this approach. Layout, Grounding and Bypassing 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 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. 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, refer to the MAX17595 evaluation kit layout available at www.maximintegrated.com. For universal AC input designs, follow all applicable safety regulations. Offline power supplies can require UL, VDE, and other similar agency approvals. COMP RZ CZ CP MAX17595 MAX17596 MAX17597 Figure 8. Error-Amplifier Compensation Network Maxim Integrated 17 MAX17595/MAX17596/ MAX17597 Peak-Current-Mode Controllers for Flyback and Boost Regulators Typical Operating Circuits R15 402k IN R16 402k VIN C5 100F 450V D1 L1 6.8mH C1 0.1F/ 275V AC 15V, 1.5A PGND R1 10 VOUT D4 T1 C9 4.7F 50V R14 402k AC1 VOUT D2 R18 100k C13 22F C10 3300pF C14 22F C15 22F C16 22F GND0 D3 IN PGND AC2 C6 0.47F C7 100nF VIN PGND SS SLOPE R9 82.5k RT SGND DITHER / SYNC VIN R3 549k R12 49.9k VFB C4 56pF R13 22k R4 549k R5 19.8k R6 4.99k SGND N1 R26 4.99k PGND MAX17595 PGND CS 1 VDRV R28 2.49k R20 100 C11 1000pF SGND SGND R2 549k NDRV SGND VOUT R19 10 2 VFB R21 R22 0.2 470 C17 68nF COMP FB VDRV SGND VDRV C8 1F U3 R29 221 SGND EN /UVLO C21 470nF OVI EP SGND SGND PGND Figure 9. MAX17595 Typical Application Circuit (Universal Offline Isolated Power Supply) www.maximintegrated.com Maxim Integrated 18 MAX17595/MAX17596/ MAX17597 Peak-Current-Mode Controllers for Flyback and Boost Regulators Typical Operating Circuits (continued) VOUT VIN VIN T1 C1 18V TO 36V 47F 63V PGND C2 4.7F 50V R1 750 C9 10F 50V C4 0.1F, 50V D1 C3 0.22F VOUT D2 C10 10F 50V C11 10F 50V C12 10F 50V C13 10F 50V 24V, 1.5A OUTPUT GND0 VIN EP SS C5 100nF NDRV SLOPE N1 R8 100 CS VFB R3 22k FB R4 49.9k C6 300pF U1 MAX17596 COMP R14 8.6k VDRV SGND VIN RT C7 1F GND0 C15 R16 16.5k 22nF VFB R13 470 C16 56pF U2 R10 28.5k EN /UVLO U3 C8 100nF OVI R12 10k C17 500nF VDRV VDRV R6 20k R15 8.6k C14 0.1F PGND R5 348k VOUT R9 50m R17 470 DITHER/ SYNC R7 10k SGND SGND PGND Figure 10. MAX17596 Typical Application Circuit (Power Supply for DC-DC Applications) www.maximintegrated.com Maxim Integrated 19 MAX17595/MAX17596/ MAX17597 Peak-Current-Mode Controllers for Flyback and Boost Regulators Typical Operating Circuits (continued) VIN VIN VIN C7 10F C1 22F 8V TO 14V DC C2 1F PGND EP SS C3 47nF C4 1F VDRV R1 32.4k R2 9.92k VIN SLOPE MAX17597 L1 6.8H FB R3 187k VOUT NDRV R4 1.96k C5 33nF COMP CS C6 330pF VIN R5 187k R6 18k VOUT 24V, 1A D1 N1 C9 4.7F/ 50V C10 4.7F/ 50V C11 4.7F/ 50V R8 100 C8 300pF R9 65m PGND RT R10 21k EN /UVLO C12 10nF DITHER OVI R7 18k SGND SGND PGND Figure 11. MAX17597 Typical Application Circuit (Nonsynchronous Boost Converter) www.maximintegrated.com Maxim Integrated 20 MAX17595/MAX17596/ MAX17597 Peak-Current-Mode Controllers for Flyback and Boost Regulators Ordering Information/Selector Guide PART TEMP RANGE PIN PACKAGE MAX17595ATE+ -40NC to +125NC 16 TQFN-EP* Offline Flyback Controller MAX17596ATE+ -40NC to +125NC 16 TQFN-EP* Low-Voltage DC-DC Flyback Controller MAX17597ATE+ -40NC to +125NC 16 TQFN-EP* Boost Controller FUNCTIONALITY UVLO, VIN CLAMP DMAX 20V, Yes 46% 4V, No 46% 4V, No 93% +Denotes a lead(Pb)-free/RoHS-compliant package. *Exposed pad. Package Information For the latest package outline information and land patterns (footprints), go to www.maximintegrated.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. 16 TQFN T1633+4 21-0136 90-0032 www.maximintegrated.com Maxim Integrated 21 MAX17595/MAX17596/ MAX17597 Peak-Current-Mode Controllers for Flyback and Boost Regulators Revision History REVISION NUMBER REVISION DATE PAGES CHANGED 0 1/12 Initial release 1 2/13 Updated General Description, Electrical Characteristics tables, Typical Operating Characteristics; Detailed Description, Figures 1, 3-6; Typical Operating Circuits, deleted sections relating to soft-stop, flyback, and boost. 1-22 2 6/13 Updated Pin Description for EP and Figure 10 10, 19 3 11/14 Deleted automotive reference in Applications section 1 4 5/15 Updated Benefits and Features section 1 5 5/17 Added reference to App Note and modified pin description DESCRIPTION -- 1, 9, For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated's website at www.maximintegrated.com. Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated 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 and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. (c) 2017 Maxim Integrated Products, Inc. 22 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Maxim Integrated: MAX17596ATE+ MAX17597ATE+T MAX17595ATE+T MAX17595ATE+ MAX17596ATE+T