MAX17497B

Obsolete

AC-DC and DC-DC Peak-Current-Mode Converters with Integrated Step-Down Regulator

Single-Chip Smart Meter Power Solution Simplifies Design and Lowers Cost

Data Sheet (Rev. 3) Product Selection Table

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Overview

Reduced Component Count and Board Space
- Flyback/Boost with Integrated Internally Compensated Step-Down Regulator
- No Current-Sense Resistor
- Space-Saving 16-Pin (3mm x 3mm) TQFN Package
Minimal Radio Interference
- 250kHz Switching in Offline Version Minimizes Interference with Radio Receivers in Smart Meter Applications
Reduced Inrush Current
- Programmable Flyback/Boost Soft-Start
- Internal Digital Soft-Start for Step-Down Regulator
Reduced Power Dissipation Under Fault
- Hiccup Mode Overcurrent Protection
- Thermal Shutdown with Hysteresis
Robust Protection Features
- Flyback/Boost Programmable Current Limit
- Input Overvoltage Protection
Optimized Loop Performance
- Programmable Slope Compensation for Flyback/Boost Maximizes Obtainable Phase Margin
High Efficiency
- Low R_DSON, 150mΩ, 65V-Rated Internal nMOSFET
- 3.3V Step-Down Regulator Efficiency Greater Than 90%
Optional Spread Spectrum

The MAX17497A/MAX17497B include both a current-mode fixed-frequency flyback converter and a synchronous step-down regulator. They contain all the control circuitry required to design wide input-voltage nonisolated power supplies to supply multiple output rails for smart meters, industrial control, and other similar applications. The MAX17497A has its rising/falling undervoltage lockout (UVLO) thresholds optimized for universal offline (85V AC to 265V AC) applications, while the MAX17497B supports undervoltage lockout (UVLO) thresholds suitable to low-voltage DC-DC applications. Both devices also include a 3.3V fixed-output synchronous step-down regulator that delivers up to 600mA load current.

The switching frequency of the MAX17497A flyback converter is 250kHz, while the MAX17497B flyback/ boost converter is 500kHz. The internally compensated synchronous step-down regulator switches at 1MHz on both versions. These frequencies allow the use of tiny magnetic and filter components resulting in compact, cost-effective power supplies. An EN/UVLO input allows the user to start the power supply precisely at the desired input voltage, while also functioning as an on/off pin. The OVI pin enables implementation of an input overvoltage-protection scheme that ensures the converter shuts down when the DC input voltage exceeds the desired maximum value.

Programmable current limit allows proper sizing and protection of the primary switching FET. The devices support a maximum duty cycle greater than 92% and provides programmable slope compensation to allow optimization of control-loop performance. The devices provide an open-drain RESETN pin that serves as a power-good indicator and enters the high-impedance state to indicate that the flyback/boost converter and 3.3V step-down regulator outputs are in regulation. An SSF pin allows programmable soft-start time for the flyback/boost converter, while an internal digital soft-start is employed for the 3.3V step-down regulator to limit inrush current. Hiccup mode overcurrent protection and thermal shutdown are provided to minimize dissipation under overcurrent and overtemperature fault conditions. The devices are available in a space-saving 16-pin (3mm x 3mm) TQFN package with 0.5mm lead spacing.

Applications

AC/DC Power Supplies for Smart Meter Applications
Universal-Input Offline AC-DC Power Supplies
Wide-Range DC Input Flyback/Boost Industrial Power Supplies

Documentation

Data Sheet 1

MAX17497A-MAX17497B: AC-DC and DC-DC Peak-Current-Mode Converters with Integrated Step-Down Regulator Data Sheet (Rev.3) 05/23/2013

This is the most up-to-date revision of the Data Sheet.

Software Resources

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Evaluation Kits

Evaluation Kit for the MAX17497A

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Features and Benefits

+85V AC to +265V AC Input Voltage Range
Dual Non-Isolated Outputs
- +12V Provides Up to 300mA (VOUT1)
- +3.3V Provides Up to 600mA (VOUT2)
250kHz Switching Frequency
RESETN Open-Drain Output
Undervoltage Lockout (UVLO)
Low-Cost Flyback Design
Proven PCB Layout
Fully Assembled and Tested

Product Details

The MAX17497A evaluation kit (EV kit) demonstrates the MAX17497A controller IC offline AC-DC flyback converter design and features an integrated step-down regulator. The EV kit circuit uses the MAX17497AATE current-mode fixed-frequency flyback converter in a 16-pin TQFN package with an exposed pad.

The EV kit demonstrates the IC's cycle-by-cycle current limit, soft-start, and UVLO features optimized for universal offline applications (+85V AC to +265V AC). The EV kit circuit is configured for output voltages of +12V and +3.3V and provides up to 300mA and 600mA of current from the respective outputs.

The transformer secondary +12V output is used as the input source for the IC step-down regulator that provides +3.3V at VOUT2.

Warning: The EV kit is designed to operate with high voltages. Dangerous voltages are present on this EV kit and on equipment connected to it. Users who power up this EV kit or power the sources connected to it must be careful to follow safety procedures appropriate to working with high-voltage electrical equipment.

Under severe fault or failure conditions, this EV kit may dissipate large amounts of power, which could result in the mechanical ejection of a component or of component debris at high velocity. Operate this kit with care to avoid possible personal injury.