MAX17498A Datasheet, PDF(1/30 Page) Maxim Integrated Products – AC-DC and DC-DC Peak-Current-Mode Converters for Flyback/Boost Applications

19-6043; Rev 1; 3/12

EVALUATION KIT AVAILABLE

MAX17498A / MAX17498B / MAX17498C

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

for Flyback/Boost Applications

General Description

The MAX17498A/MAX17498B/MAX17498C devices are

current-mode fixed-frequency flyback/boost converters

with a minimum number of external components. They

contain all the control circuitry required to design wide

input voltage isolated and nonisolated power supplies.

The MAX17498A has its rising/falling undervoltage lock-

out (UVLO) thresholds optimized for universal offline (85V

AC to 265V AC) applications, while the MAX17498B/

MAX17498C support UVLO thresholds suitable to low-

voltage DC-DC applications.

The switching frequency of the MAX17498A/MAX17498C

flyback converters is 250kHz, while that of the MAX17498B

flyback/boost converter is 500kHz. 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 function-

ing as an on/off pin. The OVI pin enables implementation

of an input overvoltage-protection scheme that ensures

that the converter shuts down when the DC input voltage

exceeds the desired maximum value.

The devices incorporate a flexible error amplifier and an

accurate reference voltage (REF) to enable the end user to

regulate both positive and negative outputs. Programmable

current limit allows proper sizing and protection of the

primary switching FET. The MAX17498B supports a maxi-

mum duty cycle of 92% and provides programmable

slope compensation to allow optimization of control-loop

performance. The MAX17498A/MAX17498C support a

maximum duty cycle of 49%, and have fixed internal slope

compensation for optimum control-loop performance. The

devices provide an open-drain PGOOD pin that serves as a

power-good indicator and enters the high-impedance state

to indicate that the flyback /boost converter is in regula-

tion. An SS pin allows programmable soft-start time for the

flyback/boost converter. 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.

Ordering Information appears at end of data sheet.

Typical Application Circuits appears at end of data sheet.

Benefits and Features

S Peak Current-Mode Flyback/Boost Converter

S Current-Mode Control Provides Excellent

Transient Response

S Fixed Switching Frequency

ï² 250kHz (MAX17498A/MAX17498C)

ï² 500kHz (MAX17498B)

S Flexible Error Amplifier to Regulate Both Positive

and Negative Outputs

S Programmable Soft-Start to Reduce Input Inrush

Current

S Programmable Voltage or Current Soft-Start

S Power-Good Signal (PGOOD)

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 175mI, 65V Rated n-Channel MOSFET Offers

Typical Efficiency Greater Than 80%

ï² No Current-Sense Resistor

S Optional Spread Spectrum

S Space-Saving, 16-Pin (3mm x 3mm) TQFN

Package

Applications

Front-End AC-DC Power Supplies for Industrial

Applications (Isolated and Nonisolated)

Telecom Power Supplies

Wide Input Range DC Input Flyback /Boost

Industrial Power Supplies

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

refer to www.maxim-ic.com/MAX17498A.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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