MAX17085B:Integrated Charger, Dual Main Step-Down Controllers, and Dual LDO Regulators

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

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.

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
MAX17085B: Functional Diagram
MAX17085B: Functional Diagram
  • 2-to-4, Li+-Cell, Battery-Powered Devices
  • 5V and 3.3V Supplies
  • Notebook Computers
  • PDAs and Mobile Communicators
titleDownload file
MAX17085B Data SheetMAX17085B.pdf
Part NumberPrimary TopologyMonitor/Control FeaturesDC-DC/Power FeaturesBattery Charger FeaturesInterface TypeVIN
Oper. Freq.
minmaxminmaxSee Notes
MAX17085BStep-DownLow Batt./POK Output
Adj. Frequency
Current Limit
Fixed Freq./PWM
Soft Start
Sync. Rectifier
Battery Charger
Input Current Limit
Smart Pwr. Selector
GPIO4.5243.35881400TQFN/40$3.44 @1k
Design kits & evaluation modules
Quality and Environmental Data
Ordering Information
Part NumberStatusRecommended ReplacementPackageTempRoHS
MAX17085BETL+ActiveTQFN,;40 pin;26 mm²-40°C to +85°CLead Free
MAX17085BETL+TActiveTQFN,;40 pin;26 mm²-40°C to +85°CLead Free
MAX17085B.pdf MAX17085B
MAX17085B.pdf MAX17085B
MAX17085B.pdf MAX17085B
MAX17085B.pdf MAX17085B
功能框图 MAX17085B