Integrated Charger, Dual Main Step-Down Controllers, and Dual LDO Regulators

All-in-One IC Solution Combines Battery Charger and System Power

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The MAX17085B is an all-in-one notebook power solution integrating a multichemistry battery charger, dual fixed output Quick-PWM™ step-down controllers, and dual keep-alive linear regulators:

  • Charger: The high-frequency (~1.4MHz) multichemistry battery charger uses a current-mode, fixed inductor current ripple architecture that significantly reduces component size and cost. Low-offset sense amplifiers allow the use of low-value sense resistors for charging and input current limit.
  • The charger uses n-channel switching MOSFETs. Adjustable charge current, charge voltage, and cell selection allow for flexible use with different battery packs. Charge current is set by an analog control input, or a PWM input. High-accuracy current-sense amplifiers provide fast cycle-by-cycle current-mode control to protect against short circuits to the battery and respond quickly to system load transients. Additionally, the charger provides a high-accuracy analog output that is proportional to the adapter current.

    An integrated charge pump controls an n-channel adapter selector switch. The charge pump remains active even when the charger is off. When the adapter is absent, a p-channel MOSFET selects the battery.

  • Main SMPS: The dual Quick-PWM step-down controllers with synchronous rectification generate the 5V and 3.3V main power in a notebook. Low-side MOSFET sensing provides a simple low-cost, highly efficient valley current-limit protection. The MAX17085B also includes output undervoltage, output overvoltage, and thermal-fault protection.
  • Separate enable inputs for each SMPS and a combined open-drain power-good output allow flexible power sequencing. Voltage soft-start reduces inrush current, while passive shutdown discharges the output through an internal switch. Fast transient response, with an extended on-time feature reduces output capacitance requirements. Selectable pulse-skipping mode and ultrasonic mode improve light-load efficiency. Ultrasonic mode operation maintains a minimum switching frequency at light loads, minimizing audible noise effects.

  • Dual LDO Regulators: An internal 5V/100mA LDO5 with switchover can be used to either generate the 5V bias needed for power-up or other lower power "always-on" suspend supplies. Another 3.3V/50mA LDO3 provides "always-on" power to a system microcontroller.
MAX17085B: Functional Diagram MAX17085B: Functional Diagram Enlarge+

Key Features

  • All-in-One Charger Plus Dual Main Step-Down Controllers
  • 5V/100mA and 3.3V/50mA LDO Regulators
  • Main
    • Dual Quick-PWM with Fast Transient Response and Extended On-Time
    • 300kHz to 800kHz Switching Frequency
    • Fixed 5V and 3.3V SMPS Outputs
    • Low-Noise Ultrasonic Mode
    • Autoretry Fault Protection
  • Charger
    • High Switching Frequency (1.4MHz)
    • Selectable 2-, 3-, and 4-Cell Battery Voltage
    • Automatic Selection of System Power Source
    • Internal Charge-Pump for Adapter n-channel MOSFETs Drive
    • ±0.4% Accurate Charge Voltage
    • ±2.5% Accurate Input Current Limiting
    • ±3% Accurate Charge Current
  • Monitor Outputs for
    • AC Adapter Current (±2% Accuracy)
    • Battery Discharge Current (±2% Accuracy)
    • AC Adapter OK
  • Analog/PWM (100Hz to 500kHz) Adjustable Charge Current Setting
  • AC Adapter Overvoltage and Overcurrent Protection


  • 2-to-4, Li+-Cell, Battery-Powered Devices
  • 5V and 3.3V Supplies
  • Notebook Computers
  • PDAs and Mobile Communicators
Part NumberPrimary TopologyMonitor/Control FeaturesDC-DC/Power FeaturesBattery Charger FeaturesInterface TypeVIN
Oper. Freq.
minmaxminmaxSee Notes
MAX17085B Step-Down
Low Batt./POK Output
Adj. Frequency
Current Limit
Fixed Freq./PWM
Soft Start
Sync. Rectifier
Battery Charger
Input Current Limit
Smart Pwr. Selector
$3.61 @1k
See All Multifunction PMICs (85)
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.

MAX17085BEVKIT: Evaluation Kit for the MAX17085B

Quality and Environmental Data

Product Reliability Reports: MAX17085B.pdf 
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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Environmental Management System >


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