The MAX5974E/MAX5974F provide control for wide-input-voltage, current-mode PWM, nonisolated, synchronous flyback converters in Power-over-Ethernet (PoE) powered device (PD) applications. The MAX5974EETE+TG3U is well-suited for universal or telecom input range, while the MAX5974F also accommodates low input voltage down to 8.4V. The devices include several features to enhance supply efficiency, including a synchronous MOSFET driver output. The AUX driver drives an output synchronous rectifier to lower conduction losses. Programmable dead time between the AUX and main driver allows for zero-voltage switching (ZVS). Under light load conditions, the devices reduce the switching frequency (frequency foldback) to reduce switching losses. An internal error amplifier with a 1% reference eliminates the need for an external shunt regulator and optocoupler. The programmable frequency dithering feature provides low-EMI, spread-spectrum operation. The MAX5974E/MAX5974F are available in 16-pin TQFN-EP packages and are rated for operation over the -40°C to +85°C temperature range.
Feature
- Peak Current-Mode Control, Synchronous Flyback PWM Controller
- Synchronous MOSFET Driver Output
- Internal 1% Error Amplifier Eliminates Shunt Regulator and Optocoupler
- 100kHz to 600kHz Programmable ±8% Switching Frequency, Synchronization Up to 1.2MHz
- Programmable Frequency Dithering for Low-EMI, Spread-Spectrum Operation
- Programmable Dead Time, PWM Soft-Start, Current Slope Compensation
- Programmable Feed-Forward Maximum Duty-Cycle Clamp, 80% Maximum Limit
- Frequency Foldback for High-Efficiency Light-Load Operation
- Internal Bootstrap UVLO with Large Hysteresis
- 100μA (typ) Startup Supply Current
- Fast Cycle-by-Cycle Peak Current-Limit, 35ns Typical Propagation Delay
- 115ns Current-Sense Internal Leading-Edge Blanking
- Output Short-Circuit Protection with Hiccup Mode
- Internal 18V Zero Clamp on Supply Input
- 3mm x 3mm, Lead-Free, 16-Pin TQFN-EP
Applications
- High-Power PD (Beyond the 802.3af/at Standard)
- IP Phones
- PoE IEEE? 802.3af/at Powered Devices
- Security Cameras
- Wireless Access Nodes
