LTC4156IUFD View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
LTC4156IUFD
Linear Technology
'LTC4156IUFD' PDF : 52 Pages View PDF
LTC4156
OPERATION
Introduction
The LTC4156 is an advanced I2C controlled power manager
and LiFePO4 battery charger designed to efficiently transfer
up to 15W from a variety of sources while minimizing power
dissipation and easing thermal budgeting constraints. By
decoupling VOUT and the battery, the innovative instant-
on PowerPath architecture ensures that the application
is powered immediately after external voltage is applied,
even with a completely dead battery, by prioritizing power
to the application.
Since VOUT and the battery are decoupled, the LTC4156
includes an ideal diode controller. The ideal diode from
the battery to VOUT guarantees that ample power is always
available to VOUT even if there is insufficient or absent
power at VBUS.
The LTC4156 includes a monolithic step-down switch-
ing battery charger for USB support, wall adapters and
other 5V sources. By incorporating a unique input current
measurement and control system, the switching charger
interfaces seamlessly to wall adapters and USB ports
without requiring application software to monitor and
adjust system loads. Because power is conserved, the
LTC4156 allows the load current on VOUT to exceed the
current drawn by the USB port or wall adapter, making
maximum use of the allowable power for battery charging
without exceeding the USB or wall adapter power delivery
specifications. A wide range of input current settings as
well as battery charge current settings are available for
selection by I2C.
Using only one inductor, the switching PowerPath can
operate in reverse, boosting the battery voltage to provide
5V power at its input pin for USB On-The-Go applications.
In the USB-OTG mode, the switching regulator supports
USB high power loads up to 500mA. Protection circuits
ensure that the current is limited and ultimately the channel
is shut down if a fault is detected on the USB connector.
To support USB low power mode, the LTC4156 can deliver
power to the external load and charge the battery through
a linear regulator while limiting input current to less than
100mA.
The LTC4156 also features a combination overvoltage
protection circuit /priority multiplexer which prevents
damage to its input caused by accidental application of
high voltage and selects one of two high power input
connectors based on priority.
A thermistor measurement subsystem periodically
monitors and reports the battery’s thermistor value via
the onboard I2C port. The same circuit then reports when
dangerous battery temperatures are reached and can
autonomously pause charging.
To minimize battery drain when a device is connected to a
suspended USB port, an LDO from VBUS to VOUT provides
the allowable USB suspend current to the application.
An interrupt subsystem can be enabled to alert the host
microprocessor of various status change events so that
system parameters can be varied as needed by system
software. Several status change event categories are
maskable for maximum flexibility.
To eliminate battery drain between manufacture and sale,
a ship-and-store feature reduces the already low battery
standby current to nearly zero and optionally disconnects
power from downstream circuitry.
An input undervoltage amplifier optionally prevents the
input voltage from decreasing below 4.3V when a resistive
cable or current limited supply is providing input power
to the LTC4156.
Finally, the LTC4156 has considerable adjustability built
in so that power levels and status information can be
controlled and monitored via the simple 2-wire I2C port.
Input Current-Limited Step-Down Switching Charger
Power delivery from VBUS to VOUT is controlled by a
2.25MHz constant-frequency step-down switching regu-
lator. The switching regulator reduces output power in
response to one of six regulation loops, including battery
voltage, battery charge current, output voltage, input cur-
rent, input undervoltage, and external PMOS charger FET
power dissipation. For USB low power (100mA) and USB
suspend (2.5mA) modes, the switching regulator is dis-
abled and power is transmitted through a linear regulator.
4156f
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