MAX17497A_12 Datasheet, PDF(1/30 Page) Maxim Integrated Products – AC-DC and DC-DC Peak-Current-Mode Converters with Integrated Step-Down Regulator

19-5981; Rev 1; 1/12

EVALUATION KIT AVAILABLE

MAX17497A/MAX17497B

AC-DC and DC-DC Peak-Current-Mode Converters

with Integrated Step-Down Regulator

General Description

Benefits and Features

The MAX17497A/MAX17497B include both a current-

mode fixed-frequency PWM converter and a synchro-

nous step-down regulator. They contain all the control

circuitry required to design wide-input-voltage noniso-

lated power supplies to supply multiple output rails for

smart meters, industrial control, and other similar applica-

tions. 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 suit-

able 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 MAX17497B

supports a maximum duty cycle of 93% and provides

programmable slope compensation to allow optimization

of control loop performance. The MAX17497A supports

a maximum duty cycle of 49%, and has a fixed internal

slope compensation for optimum control loop perfor-

mance. 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 regu-

lator to limit inrush current. Hiccup mode overcurrent pro-

tection 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.

S Reduced Component Count and Board Space

ï² Flyback/Boost with Integrated Internally

Compensated Step-Down Regulator

ï² No Current-Sense Resistor

ï² Space-Saving 16-Pin (3mm x 3mm) TQFN

Package

S Minimal Radio Interference

ï² 250kHz Switching in Offline Version

Minimizes Interference with Radio Receivers

in Smart Meter Applications

S Reduced Inrush Current

ï² Programmable Flyback/Boost Soft-Start

ï² Internal Digital Soft-Start for Step-Down

Regulator

S Reduced Power Dissipation Under Fault

ï² Hiccup Mode Overcurrent Protection

ï² Thermal Shutdown with Hysteresis

S Robust Protection Features

ï² Flyback/Boost Programmable Current Limit

ï² Input Overvoltage Protection

S Optimized Loop Performance

ï² Programmable Slope Compensation for

Flyback/Boost Maximizes Obtainable Phase

Margin

S High Efficiency

ï² 150mI, 65V-Rated nMOSFET Offers Typical

Flyback Converter Efficiency Greater Than

80%

ï² 3.3V Step-Down Regulator Efficiency Greater

Than 90%

S Optional Spread Spectrum

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

Ordering Information appears at end of data sheet.

For related parts and recommended products to use with this part,

refer to www.maxim-ic.com/MAX17497A.related.

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maximâs website at www.maxim-ic.com.

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