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1A/2.7A, 1MHz, Step-Down Regulators with Synchronous Rectification and Internal Switches

Product Details

The MAX1742/MAX1842 constant-off-time, pulse-width- modulated (PWM) step-down DC-DC converters are ideal for use in 5V and 3.3V to low-voltage conversion necessary in notebook and subnotebook computers. These devices feature internal synchronous rectification for high efficiency and reduced component count. They require no external Schottky diode. The internal 90mΩ PMOS power switch and 70mΩ NMOS synchronous-rectifier switch easily deliver continuous load currents up to 1A. The MAX1742/MAX1842 produce a preset 2.5V, 1.8V, or 1.5V output voltage or an adjustable output from 1.1V to VIN. They achieve efficiencies as high as 95%.

The MAX1742/MAX1842 use a unique current-mode, constant-off-time, PWM control scheme, which includes Idle Mode™ to maintain high efficiency during light-load operation. The programmable constant-off-time architecture sets switching frequencies up to 1MHz, allowing the user to optimize performance trade-offs between efficiency, output switching noise, component size, and cost. Both devices are designed for continuous output currents up to 1A. The MAX1742 uses a peak current limit of 1.3A (min) and is suitable for applications requiring small external component size and high efficiency. The MAX1842 has a higher current limit of 3.1A (min) and is intended for applications requiring an occasional burst of output current up to 2.7A. Both devices also feature an adjustable soft-start to limit surge currents during startup, a 100% duty cycle mode for low-dropout operation, and a low-power shutdown mode that disconnects the input from the output and reduces supply current below 1µA. The MAX1742/MAX1842 are available in 16-pin QSOP packages.

For similar devices that provide continuous output currents up to 2A and 3A, refer to the MAX1644 and MAX1623 data sheets.

Key Features

  • ±1% Output Accuracy
  • 95% Efficiency
  • Internal PMOS and NMOS Switches
    • 90mΩ On-Resistance at VIN = 4.5V
    • 110mΩ On-Resistance at VIN = 3V
  • Output Voltage
    • 2.5V, 1.8V, or 1.5V Pin Selectable
    • 1.1V to VIN Adjustable
  • 3V to 5.5V Input Voltage Range
  • 600µA (max) Operating Supply Current
  • <1µA Shutdown Supply Current
  • Programmable Constant-Off-Time Operation
  • 1MHz (max) Switching Frequency
  • Idle-Mode Operation at Light Loads
  • Thermal Shutdown
  • Adjustable Soft-Start Inrush Current Limiting
  • 100% Duty Cycle During Low-Dropout Operation
  • Output Short-Circuit Protection
  • 16-Pin QSOP Package

Applications/Uses

  • 5V or 3.3V to Low-Voltage Conversion
  • Chipset Supplies
  • CPU I/O Ring
  • Notebook and Subnotebook Computers
Parametric specs for Step-Down (Buck) Switching Regulators
VIN (V) (min) 3
VIN (V) (max) 5.5
VOUT1 (V) (min) 1.1
VOUT1 (V) (max) 5.5
IOUT1 (A) (max) 1
Switch Type Internal
Preset VOUT (V) 1.5
1.8
2.5
Output Adjust. Method Preset
Resistor
Synchronous Switching? Yes
# DC-DC Outputs 1
Switching Frequency (kHz) 1000
Package/Pins QSOP/16
Budgetary
Price (See Notes)
$4.42 @1k
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Simplified Block Diagram

MAX1742, MAX1842: Typical Configuration MAX1742, MAX1842: Typical Configuration Zoom icon

Technical Docs

Design & Development

Click any title below to view the detail page where available.

Description

The MAX1742 and MAX1842 evaluation kits (EV kits) provide a +1.8V adjustable output voltage from a +3V to +5.5V input source. The MAX1742 delivers up to 1A of output current, and the MAX1842 delivers up to 2.5A of output current.

The MAX1742/MAX1842 are step-down switching regulators with internal synchronous-rectifiers that operate up to 1MHz, which minimizes external components. The devices feature resistor-programmable, fixed off-time current-mode operation for superior load- and line-transient response, and achieve efficiencies up to 95%.

The MAX1742/MAX1842 EV kits can also be used to evaluate other output voltages by adding feedback resistors R1 and R2 or by using the jumper-selectable +1.1V, +1.5V, +1.8V, or +2.5V settings.

View Details

Features

  • 1A Output Current for MAX1742
    2.5A Output Current for MAX1842
  • Up to 1MHz Switching Frequency
  • Up to 95% Efficiency
  • Synchronous Rectification for Improved Efficiency
  • No External Schottky Diode Required
  • Output Voltage
    • +1.1V, +1.5V, +1.8V, or +2.5V Selectable
    • +1.1V to VIN Adjustable
  • +3V to +5.5V Input Voltage Range
  • < 1µA (typ) IC Shutdown Current
  • Surface-Mount Construction
  • Fully Assembled and Tested

Description

The MAX1742 and MAX1842 evaluation kits (EV kits) provide a +1.8V adjustable output voltage from a +3V to +5.5V input source. The MAX1742 delivers up to 1A of output current, and the MAX1842 delivers up to 2.5A of output current.

The MAX1742/MAX1842 are step-down switching regulators with internal synchronous-rectifiers that operate up to 1MHz, which minimizes external components. The devices feature resistor-programmable, fixed off-time current-mode operation for superior load- and line-transient response, and achieve efficiencies up to 95%.

The MAX1742/MAX1842 EV kits can also be used to evaluate other output voltages by adding feedback resistors R1 and R2 or by using the jumper-selectable +1.1V, +1.5V, +1.8V, or +2.5V settings.

View Details

Features

  • 1A Output Current for MAX1742
    2.5A Output Current for MAX1842
  • Up to 1MHz Switching Frequency
  • Up to 95% Efficiency
  • Synchronous Rectification for Improved Efficiency
  • No External Schottky Diode Required
  • Output Voltage
    • +1.1V, +1.5V, +1.8V, or +2.5V Selectable
    • +1.1V to VIN Adjustable
  • +3V to +5.5V Input Voltage Range
  • < 1µA (typ) IC Shutdown Current
  • Surface-Mount Construction
  • Fully Assembled and Tested

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Parameters

Parametric specs for Step-Down (Buck) Switching Regulators
VIN (V) (min) 3
VIN (V) (max) 5.5
VOUT1 (V) (min) 1.1
VOUT1 (V) (max) 5.5
IOUT1 (A) (max) 1
Switch Type Internal
Preset VOUT (V) 1.5
1.8
2.5
Output Adjust. Method Preset
Resistor
Synchronous Switching? Yes
# DC-DC Outputs 1
Switching Frequency (kHz) 1000
Package/Pins QSOP/16
Budgetary
Price (See Notes)
$4.42 @1k

Key Features

  • ±1% Output Accuracy
  • 95% Efficiency
  • Internal PMOS and NMOS Switches
    • 90mΩ On-Resistance at VIN = 4.5V
    • 110mΩ On-Resistance at VIN = 3V
  • Output Voltage
    • 2.5V, 1.8V, or 1.5V Pin Selectable
    • 1.1V to VIN Adjustable
  • 3V to 5.5V Input Voltage Range
  • 600µA (max) Operating Supply Current
  • <1µA Shutdown Supply Current
  • Programmable Constant-Off-Time Operation
  • 1MHz (max) Switching Frequency
  • Idle-Mode Operation at Light Loads
  • Thermal Shutdown
  • Adjustable Soft-Start Inrush Current Limiting
  • 100% Duty Cycle During Low-Dropout Operation
  • Output Short-Circuit Protection
  • 16-Pin QSOP Package

Applications/Uses

  • 5V or 3.3V to Low-Voltage Conversion
  • Chipset Supplies
  • CPU I/O Ring
  • Notebook and Subnotebook Computers

Description

The MAX1742/MAX1842 constant-off-time, pulse-width- modulated (PWM) step-down DC-DC converters are ideal for use in 5V and 3.3V to low-voltage conversion necessary in notebook and subnotebook computers. These devices feature internal synchronous rectification for high efficiency and reduced component count. They require no external Schottky diode. The internal 90mΩ PMOS power switch and 70mΩ NMOS synchronous-rectifier switch easily deliver continuous load currents up to 1A. The MAX1742/MAX1842 produce a preset 2.5V, 1.8V, or 1.5V output voltage or an adjustable output from 1.1V to VIN. They achieve efficiencies as high as 95%.

The MAX1742/MAX1842 use a unique current-mode, constant-off-time, PWM control scheme, which includes Idle Mode™ to maintain high efficiency during light-load operation. The programmable constant-off-time architecture sets switching frequencies up to 1MHz, allowing the user to optimize performance trade-offs between efficiency, output switching noise, component size, and cost. Both devices are designed for continuous output currents up to 1A. The MAX1742 uses a peak current limit of 1.3A (min) and is suitable for applications requiring small external component size and high efficiency. The MAX1842 has a higher current limit of 3.1A (min) and is intended for applications requiring an occasional burst of output current up to 2.7A. Both devices also feature an adjustable soft-start to limit surge currents during startup, a 100% duty cycle mode for low-dropout operation, and a low-power shutdown mode that disconnects the input from the output and reduces supply current below 1µA. The MAX1742/MAX1842 are available in 16-pin QSOP packages.

For similar devices that provide continuous output currents up to 2A and 3A, refer to the MAX1644 and MAX1623 data sheets.

Simplified Block Diagram

MAX1742, MAX1842: Typical Configuration MAX1742, MAX1842: Typical Configuration 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.