MAX5974A/MAX5974B/MAX5974C/MAX5974D 19-5331 Rev 2 6/11 Active-Clamped, Spread-Spectrum, Current-Mode PWM Controllers General Description Features S Peak Current-Mode Control, Active-Clamped The MAX5974 provide control for wide-input-voltage, Forward PWM Controller active-clamped, current-mode PWM, forward converters in Power-over-Ethernet (PoE) powered device (PD) appli- S Regulation Without Optocoupler (MAX5974A/ cations. The MAX5974A/MAX5974C are well-suited for MAX5974B) universal or telecom input range, while the MAX5974B/ S Internal 1% Error Amplifier MAX5974D also accommodate low input voltage down S 100kHz to 600kHz Programmable Q8% Switching to 10.5V. Frequency, Synchronization Up to 1.2MHz The devices include several features to enhance supply S Programmable Frequency Dithering for Low-EMI, efficiency. The AUX driver recycles magnetizing cur- Spread-Spectrum Operation rent instead of wasting it in a dissipative clamp circuit. S Programmable Dead Time, PWM Soft-Start, Programmable dead time between the AUX and main Current Slope Compensation driver allows for zero-voltage switching (ZVS). Under light- S Programmable Feed-Forward Maximum Duty- load conditions, the devices reduce the switching fre- Cycle Clamp, 80% Maximum Limit quency (frequency foldback) to reduce switching losses. S Frequency Foldback for High-Efficiency Light- The MAX5974A/MAX5974B feature unique circuitry to Load Operation achieve output regulation without using an optocoupler, S Internal Bootstrap UVLO with Large Hysteresis while the MAX5974C/MAX5974D utilize the traditional S 100A (typ) Startup Supply Current optocoupler feedback method. An internal error amplifier S Fast Cycle-by-Cycle Peak Current-Limit, 35ns with a 1% reference is very useful in nonisolated design, Typical Propagation Delay eliminating the need for an external shunt regulator. S 115ns Current-Sense Internal Leading-Edge The devices feature a unique feed-forward maximum Blanking duty-cycle clamp that makes the maximum clamp volt- S Output Short-Circuit Protection with Hiccup Mode age during transient conditions independent of the line voltage, allowing the use of a power MOSFET with lower S Reverse Current Limit to Prevent Transformer breakdown voltage. The programmable frequency dither- Saturation Due to Reverse Current ing feature provides low-EMI, spread-spectrum operation. S Internal 18V Zener Clamp on Supply Input The MAX5974 are available in 16-pin TQFN-EP pack- S 3mm x 3mm, Lead-Free, 16-Pin TQFN-EP ages and are rated for operation over the -40C to +85C temperature range. Applications PoE IEEE 802.3af/at Powered Devices High-Power PD (Beyond the 802.3af/at Standard) Active-Clamped Forward DC-DC Converters IP Phones Wireless Access Nodes Security Cameras Ordering Information/Selector Guide PART TOP MARK PIN-PACKAGE UVLO THRESHOLD (V) FEEDBACK MODE MAX5974AETE+ +AHY 16 TQFN-EP* 16 Sample/Hold MAX5974BETE+ +AHZ 16 TQFN-EP* 8.4 Sample/Hold MAX5974CETE+ +AIA 16 TQFN-EP* 16 Continuously Connected MAX5974DETE+ +AIB 16 TQFN-EP* 8.4 Continuously Connected Note: All devices are specified over the -40C to +85C operating temperature range. +Denotes a lead(Pb)-free/RoHS-compliant package. *EP = Exposed pad. IEEE is a registered service mark of the Institute of Electrical and Electronics Engineers, Inc. Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com. EVALUATION KIT AVAILABLEActive-Clamped, Spread-Spectrum, Current-Mode PWM Controllers ABSOLUTE MAXIMUM RATINGS IN to GND (V = 0V) ...........................................-0.3V to +26V IN, NDRV, AUXDRV ......................................................100mA EN NDRV, AUXDRV (pulsed for less than 100ns) ..................Q1A EN, NDRV, AUXDRV to GND .....................-0.3V to (V + 0.3V) IN RT, DT, FFB, COMP, SS, DCLMP, DITHER/SYNC Continuous Power Dissipation (T = +70NC) (Note 1) A to GND .................................................................-0.3V to +6V 16-Pin TQFN (derate 20.8mW/NC above +70NC) .......1666mW FB to GND (MAX5974A/MAX5974B only) ..................-6V to +6V Operating Temperature Range .......................... -40NC to +85NC FB to GND (MAX5974C/MAX5974D only) ..............-0.3V to +6V Maximum Junction Temperature .....................................+150NC CS, CSSC to GND ...................................................-0.8V to +6V Storage Temperature Range ............................ -65NC to +150NC PGND to GND ......................................................-0.3V to +0.3V Lead Temperature (soldering, 10s) ................................+300NC Maximum Input/Output Current (continuous) 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 (B ) ..............48NC/W JA Junction-to-Case Thermal Resistance (B ) .....................7NC/W JC 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.maxim-ic.com/thermal-tutorial. ELECTRICAL CHARACTERISTICS (V = 12V (for MAX5974A/MAX5974C, bring V up to 17V for startup), V = V = V = V = V = V = IN IN CS CSSC DITHER/SYNC FB FFB DCLMP V , V = +2V, NDRV = AUXDRV = SS = COMP = unconnected, R = 34.8kI, R = 25kI, C = 1FF, T = -40NC to +85NC, GND EN RT DT IN A unless otherwise noted. Typical values are at T = +25NC.) (Note 2) A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS UNDERVOLTAGE LOCKOUT/STARTUP (IN) MAX5974A/ 15.4 16 16.5 MAX5974C Bootstrap UVLO Wakeup Level V V rising V INUVR IN MAX5974B/ 8 8.4 8.85 MAX5974D Bootstrap UVLO Shutdown V V falling 6.65 7 7.35 V INUVF IN Level IN Clamp Voltage V I = 2mA (sinking) 17 18.5 20 V IN CLAMP IN V = +15V (for MAX5974A/ IN IN Supply Current in MAX5974C) I 100 150 FA START Undervoltage Lockout V = +7.5V (for MAX5974B/MAX5974D), IN when in bootstrap UVLO IN Supply Current After Startup I V = +12V 1.8 3 mA C IN ENABLE (EN) V V rising 1.17 1.215 1.26 ENR EN Enable Threshold V V V falling 1.09 1.14 1.19 ENF EN Input Current I 1 FA EN OSCILLATOR (RT) RT Bias Voltage V 1.23 V RT NDRV Switching Frequency f 100 600 kHz SW Range 2 MAX5974A/MAX5974B/MAX5974C/MAX5974D