MAX5975A/MAX5975B 19-5545 Rev 0 9/10 Current-Mode PWM Controllers with Frequency Dithering for EMI-Sensitive Power Supplies General Description Features The MAX5975 current-mode PWM controllers contain S Peak Current-Mode Control, Forward/Flyback all the control circuitry required for the design of wide- PWM Controllers input-voltage forward and flyback power supplies in S Internal 1% Error Amplifier Power-over-Ethernet (PoE) IEEE 802.3af/at powered S 100kHz to 600kHz Programmable 8% Switching devices. The MAX5975A is well-suited for universal input Frequency (rectified 85V AC to 265V AC) or telecom (-36V DC to S Switching Frequency Synchronization Up to -72V DC) power supplies. The MAX5975B is available for low-voltage supplies (12V to 24V) such as wall adapters. 1.2MHz The devices are suitable for both isolated and noniso- S Programmable Frequency Dithering for Low-EMI Spread-Spectrum Operation lated designs. Because the devices have an internal error amplifier with a 1% accurate reference, they can be used S PWM Soft-Start, Current Slope Compensation in nonisolated power supplies without the need for an S Programmable Feed-Forward Maximum Duty- external shunt regulator. Cycle Clamp, 80% Maximum Limit An enable input (EN) is used to shut down the devices. S Frequency Foldback for High-Efficiency Light- Programmable soft-start eliminates output voltage over- Load Operation shoot. The MAX5975A has an internal bootstrap UVLO S Internal Bootstrap UVLO with Large Hysteresis with large hysteresis that requires 20V for startup, while the MAX5975B requires 10V for startup. S 100A (typ) Startup Supply Current The switching frequency for the ICs is programmable S Fast Cycle-by-Cycle Peak Current-Limit, 35ns from 100kHz to 600kHz with an external resistor. For Typical Propagation Delay EMI-sensitive design, use the programmable frequency S 115ns Current-Sense Internal Leading-Edge dithering feature for low-EMI spread-spectrum opera- Blanking tion. The duty cycle is also programmable up to the 80% S Output Short-Circuit Protection with Hiccup Mode maximum duty-cycle limit. These devices are available in 16-lead TQFN packages and are rated for operation over S 3mm x 3mm, Lead-Free, 16-Pin TQFN the -40C to +85C temperature range. Applications PoE IEEE 802.3af/at Powered Devices Flyback/Forward DC-DC Converters IP Phones Wireless Access Nodes Security Cameras Power Devices in PoE/Power-over-MDI Ordering Information PART TEMP RANGE PIN-PACKAGE TOP MARK UVLO THRESHOLD (V) MAX5975AETE+ -40C to +85C 16 TQFN-EP* +AIC 20 MAX5975BETE+ -40C to +85C 16 TQFN-EP* +AID 10 +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.Current-Mode PWM Controllers with Frequency Dithering for EMI-Sensitive Power Supplies ABSOLUTE MAXIMUM RATINGS IN to GND ..............................................................-0.3V to +26V Continuous Power Dissipation (T = +70NC) (Note 1) A 16-Pin TQFN (derate 20.8mW/NC above +70NC) .......1666mW EN, NDRV to GND ......................................-0.3V to (V + 0.3V) IN RT, FFB, COMP, SS, DCLMP, DITHER/SYNC Junction-to-Case Thermal Resistance (B ) (Note 1) JC to GND .................................................................-0.3V to +6V 16-Pin TQFN ................................................................ +7NC/W FB to GND ...............................................................-0.3V to +6V Junction-to-Ambient Thermal Resistance (B ) (Note 1) JA CS, CSSC to GND ...................................................-0.8V to +6V 16-Pin TQFN .............................................................. +48NC/W PGND to GND ......................................................-0.3V to +0.3V Operating Temperature Range .......................... -40NC to +85NC Maximum Input/Output Current (continuous) Maximum Junction Temperature .....................................+150NC NDRV ............................................................................100mA Storage Temperature Range ............................ -65NC to +150NC NDRV (pulsed for less than 100ns) ..................................Q1A Lead Temperature (soldering, 10s) ................................+300NC Soldering Temperature (reflow) ......................................+260NC 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. 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 (V = 12V (for MAX5975A, bring V up to 21V for startup), V = V = V = V = V = V = V , V = IN IN CS CSSC DITHER/SYNC FB FFB DCLMP GND EN +2V, NDRV = SS = COMP = unconnected, R = 34.8kI, C = 1FF, T = -40NC to +85NC, unless otherwise noted. Typical values RT IN A are at T = +25NC.) (Note 2) A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS UNDERVOLTAGE LOCKOUT/STARTUP (IN) MAX5975A 19.1 19.8 20.4 Bootstrap UVLO Wakeup Level V V rising V INUVR IN MAX5975B 9.4 9.8 10.25 Bootstrap UVLO Shutdown V V falling 6.65 7 7.35 V INUVF IN Level V = +18V (for MAX5975A) IN IN Supply Current in I V = +9V (for MAX597BA), 100 150 FA START IN Undervoltage Lockout 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 EN FA OSCILLATOR (RT) RT Bias Voltage V 1.23 V RT NDRV Switching Frequency f 100 600 kHz SW Range NDRV Switching Frequency -8 +8 % Accuracy Maximum Duty Cycle D f = 250kHz 81 82.5 84 % MAX SW 2 MAX5975A/MAX5975B