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AC-DC and DC-DC Peak-Current-Mode Converters for Flyback/Boost Applications

Peak-Current-Mode Converters Enable Compact, Cost-Effective, and Highly Flexible Isolated/Nonisolated Power Supplies

Product Details

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 lockout (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 is 250kHz, while that of the MAX17498B 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 functioning 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 devices support a maximum duty cycle greater than 92% and provide programmable slope compensation to allow optimization of 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 regulation. An SS pin allows programmable soft-start time for the flyback/boost converter. 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.

Key Features

  • Peak Current-Mode Converter
  • Current-Mode Control Provides Excellent Transient Response
  • Fixed Switching Frequency
    • 250kHz: MAX17498A/MAX17498C
    • 500kHz: MAX17498B
  • Flexible Error Amplifier to Regulate Both Positive and Negative Outputs
  • Programmable Soft-Start to Reduce Input Inrush Current
  • Programmable Voltage or Current Soft-Start
  • Power-Good Signal (PGOOD)
  • Reduced Power Dissipation Under Fault
    • Overcurrent Protection
    • Thermal Shutdown with Hysteresis
  • Robust Protection Features
    • Programmable Current Limit
    • Input Overvoltage Protection
  • Optimized Loop Performance
    • Programmable Slope Compensation
  • High Efficiency
    • Low RDSON, 175mΩ, 65V Rated Internal n-Channel MOSFET
    • No Current-Sense Resistor
  • Optional Spread Spectrum
  • Space-Saving, 16-Pin (3mm x 3mm) TQFN Package

Applications/Uses

  • 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
Parametric specs for Isolated Power Supplies
VIN (V) (min) 4.5
VIN (V) (max) 1000
Topology Flyback
Application (VIN) Networking (48V)
Power Over Ethernet (32-58V)
Telecom (36-72V)
Universal Off-line (90-240VAC)
Switch Type -
Control Loop Current Mode
Feedback Linear
Opto
Switching Frequency (kHz) 250
Duty Cycle (%) (max) 49
Oper. Temp. (°C) -40 to +125
Package/Pins TQFN/16
Budgetary
Price (See Notes)
$1.10 @1k
Parametric specs for Step-Up Switching Regulators
VIN (V) (min) 4.5
VIN (V) (max) 36
VOUT1 (V) (min) 1.25
VOUT1 (V) (max) 65
IOUT1 (A) (max) 2
Switch Type Internal
Output Adjust. Method Resistor
Power Good Signal Yes
Synchronous Switching? Yes
ICC (mA) (typ) 2
# DC-DC Outputs 1
Switching Frequency (kHz) 500
Package/Pins TQFN/16
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Simplified Block Diagram

MAX17498A/MAX17498B/MAX17498C: Boost Power Supply MAX17498A/MAX17498B/MAX17498C: Boost Power Supply Zoom icon

Technical Docs

Design & Development

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Additional Resources
Download SIMPLIS model ›

Description

The MAX17498B evaluation kit (EV kit) is a fully assembled and tested circuit board that contains an isolated 7W flyback DC-DC converter. The circuit uses the MAX17498B 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.

The EV kit circuit output is configured for an isolated +5V and provides up to 1.5A of current. Low cost and high efficiency up to 88% are achieved using a flyback DC-DC converter topology operating at a fixed 500kHz switching frequency. The surface-mount transformer provides up to +1500V galvanic isolation at the output.

The EV kit operates from a +18V to +36V power supply capable of providing up to 1A.

View Details

Features

  • +18V to +36V DC Voltage Input Range
  • Isolated 5V, 1.5A Output
  • Fixed 500kHz Switching Frequency
  • 88% Efficiency
  • Cycle-by-Cycle Current Limit
  • High-Accuracy UVLO
  • PGOOD Open-Drain Output
  • Low-Cost Flyback Design
  • Configurable for Primary-Side Regulation
  • Proven PCB Layout
  • Fully Assembled and Tested

Description

The MAX17498BB evaluation kit (EV kit) is a fully assembled and tested surface-mount circuit board to evaluate the MAX17498B peak-current-mode controller in a stepup (boost) configuration. The EV kit output is configured for 24V output voltage, which can supply up to 100mA of current. The input voltage range is from 4.5V to 10V.
The EV kit features a 500kHz fixed frequency for optimum efficiency and component size. High efficiency up to 94.2% is achieved using a boost converter, providing an output power up to 2.4W.

View Details

Features

  • 4.5V to 10V Input Range
  • Output Voltage: 24V at 100mA
  • 500kHz Switching Frequency
  • Integrated n-Channel MOSFET
  • Efficiency Up to 94.2%
  • Resistor-Programmable UVLO/OVI Threshold
  • Open-Drain Power-Good Signal (PGOOD)
  • Low-Cost Boost Converter Design
  • Proven PCB Layout
  • Fully Assembled and Tested

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Parameters

Parametric specs for Isolated Power Supplies
VIN (V) (min) 4.5
VIN (V) (max) 1000
Topology Flyback
Application (VIN) Networking (48V)
Power Over Ethernet (32-58V)
Telecom (36-72V)
Universal Off-line (90-240VAC)
Switch Type -
Control Loop Current Mode
Feedback Linear
Opto
Switching Frequency (kHz) 250
Duty Cycle (%) (max) 49
Oper. Temp. (°C) -40 to +125
Package/Pins TQFN/16
Budgetary
Price (See Notes)
$1.10 @1k
Parametric specs for Step-Up Switching Regulators
VIN (V) (min) 4.5
VIN (V) (max) 36
VOUT1 (V) (min) 1.25
VOUT1 (V) (max) 65
IOUT1 (A) (max) 2
Switch Type Internal
Output Adjust. Method Resistor
Power Good Signal Yes
Synchronous Switching? Yes
ICC (mA) (typ) 2
# DC-DC Outputs 1
Switching Frequency (kHz) 500
Package/Pins TQFN/16

Key Features

  • Peak Current-Mode Converter
  • Current-Mode Control Provides Excellent Transient Response
  • Fixed Switching Frequency
    • 250kHz: MAX17498A/MAX17498C
    • 500kHz: MAX17498B
  • Flexible Error Amplifier to Regulate Both Positive and Negative Outputs
  • Programmable Soft-Start to Reduce Input Inrush Current
  • Programmable Voltage or Current Soft-Start
  • Power-Good Signal (PGOOD)
  • Reduced Power Dissipation Under Fault
    • Overcurrent Protection
    • Thermal Shutdown with Hysteresis
  • Robust Protection Features
    • Programmable Current Limit
    • Input Overvoltage Protection
  • Optimized Loop Performance
    • Programmable Slope Compensation
  • High Efficiency
    • Low RDSON, 175mΩ, 65V Rated Internal n-Channel MOSFET
    • No Current-Sense Resistor
  • Optional Spread Spectrum
  • Space-Saving, 16-Pin (3mm x 3mm) TQFN Package

Applications/Uses

  • 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

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 lockout (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 is 250kHz, while that of the MAX17498B 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 functioning 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 devices support a maximum duty cycle greater than 92% and provide programmable slope compensation to allow optimization of 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 regulation. An SS pin allows programmable soft-start time for the flyback/boost converter. 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.

Simplified Block Diagram

MAX17498A/MAX17498B/MAX17498C: Boost Power Supply MAX17498A/MAX17498B/MAX17498C: Boost Power Supply Zoom icon

Technical Docs

Support & Training

Search our knowledge base for answers to your technical questions.

Filtered Search

Our dedicated team of Applications Engineers are also available to answer your technical questions. Visit our support portal