MAX8745A

High-Efficiency, Quad Output, Main Power-Supply Controllers for Notebook Computers


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Description

The MAX8744A/MAX8745A are dual step-down, switch-mode, power-supply (SMPS) controllers with synchronous rectification, intended for main 5V/3.3V power generation in battery-powered systems. Fixed-frequency operation with optimal interleaving minimizes input ripple current from the lowest input voltages up to the 26V maximum input. Optimal 40/60 interleaving allows the input voltage to go down to 8.3V before duty-cycle overlap occurs, compared to 180° out-of-phase regulators where the duty-cycle overlap occurs when the input drops below 10V.

Output current sensing provides peak current-limit protection, using either an accurate sense resistor or using lossless inductor DCR current sensing. A low-noise mode maintains high light-load efficiency while keeping the switching frequency out of the audible range.

An internal, fixed 5V, 100mA linear regulator powers up the MAX8744A/MAX8745A and their gate drivers, as well as external keep-alive loads. When the main PWM regulator is in regulation, an automatic bootstrap switch bypasses the internal linear regulator, providing current up to 200mA. An additional adjustable linear-regulator driver with an external pnp transistor can be used with a secondary winding to provide a 12V supply, or powered directly from the main outputs to generate low-voltage outputs as low as 1V.

Independent enable controls and power-good signals allow flexible power sequencing. Voltage soft-start gradually ramps up the output voltage and reduces inrush current, while soft-shutdown gradually ramps the output voltage down, preventing negative voltage dips. The MAX8744A/MAX8745A feature output undervoltage and thermal-fault protection. The MAX8744A also includes output overvoltage-fault protection.

The MAX8744A/MAX8745A are available in a 32-pin, 5mm x 5mm, thin QFN package. The exposed backside pad improves thermal characteristics for demanding linear keep-alive applications.
MAX8744A, MAX8745A: Standard Application Circuit MAX8744A, MAX8745A: Standard Application Circuit Enlarge+

Key Features

  • Fixed-Frequency, Current-Mode Control
  • 40/60 Optimal Interleaving
  • Internal BST Switches
  • Internal 5V, 100mA Linear Regulator
  • Auxiliary Linear-Regulator Driver (12V or Adjustable Down to 1V)
  • Dual Mode™ Feedback—3.3V/5V Fixed or Adjustable Output Voltages
  • 200kHz/300kHz/500kHz Switching Frequency
  • Undervoltage and Thermal-Fault Protection
  • Overvoltage-Fault Protection (MAX8744A Only)
  • 6V to 26V Input Range
  • 2V ±0.75% Reference Output
  • Independent Enable Inputs and Power-Good Outputs
  • Soft-Start and Soft-Shutdown (Voltage Ramp)
  • 8µA (typ) Shutdown Current

Applications/Uses

  • 2 to 4 Li+ Cell Battery-Powered Devices
  • Main Power Supplies
  • Notebook and Subnotebook Computers
  • PDAs and Mobile Communicators
Part NumberVIN
(V)
VIN
(V)
VOUT1
(V)
VOUT1
(V)
Preset VOUT
(V)
Output Adjust. MethodIOUT1
(A)
Switch TypeSynchronous SwitchingPower Good SignalDC-DC OutputsOper. Freq.
(kHz)
Package/Pins
minmaxminmaxmax
MAX8745A 62625.5
3.3
5
Preset
Resistor
6ExternalYesYes2500
SOIC(N)/8
See All Step-Down Switching Regulators (404)
Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

Quality and Environmental Data

Request Reliability Report for: MAX8745A 
Lead-Free Package Tin (Sn) Whisker Reports
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C  

Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

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