19-5135; Rev 2; 3/12
Integrated Charger, Dual Main Step-Down
Controllers, and Dual LDO Regulators
General Description
Features
S All-in-One Charger Plus Dual Main Step-Down
The MAX17085B is an all-in-one notebook power solution
integrating a multichemistry battery charger, dual fixed-
output Quick-PWMK step-down controllers, and dual
keep-alive linear regulators:
Controllers
S 5V/100mA and 3.3V/50mA LDO Regulators
S Main
Charger: The high-frequency (~1.4MHz) multichem-
istry 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.
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
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 ampli-
fiers 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 char-
ger provides a high-accuracy analog output that is pro-
portional to the adapter current.
S 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
Q0.4% Accurate Charge Voltage
Q2.5% Accurate Input Current Limiting
Q3% Accurate Charge Current
S Monitor Outputs for
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.
AC Adapter Current (Q2% Accuracy)
Battery Discharge Current (Q2% Accuracy)
AC Adapter OK
S Analog/PWM (100Hz to 500kHz) Adjustable
Main SMPS: The dual Quick-PWM step-down con-
trollers 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, out-
put overvoltage, and thermal-fault protection.
Charge Current Setting
S AC Adapter Overvoltage and Overcurrent
Protection
Applications
Notebook Computers
PDAs and Mobile Communicators
5V and 3.3V Supplies
Separate enable inputs for each SMPS and a com-
bined open-drain power-good output allow flex-
ible 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, mini-
mizing audible noise effects.
2-to-4, Li+-Cell, Battery-Powered Devices
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX17085BETL+
-40°C to +85°C
40 TQFN-EP*
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
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.
Pin Configuration appears at end of data sheet.
Quick-PWM is a trademark of Maxim Integrated Products, Inc.
_______________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
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