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LTC3577_15 Datasheet, PDF (18/54 Pages) Linear Technology – Highly Integrated 6-Channel Portable PMIC
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LTC3577/LTC3577-1
PIN FUNCTIONS
VBUS (Pin 40): USB Input Voltage. VBUS will usually be
connected to the USB port of a computer or a DC output
wall adapter. VBUS should be bypassed with a low imped-
ance multilayer ceramic capacitor.
ACPR (Pin 41): Wall Adapter Present Output (Active Low).
A low on this pin indicates that the wall adapter input com-
parator has had its input pulled above its input threshold
(typically 4.3V). This pin can be used to drive the gate of
an external P-channel MOSFET to provide power to VOUT
from a power source other than a USB port.
VC (Pin 42): High Voltage Buck Regulator Control Pin.
This pin can be used to drive the VC pin of an approved
external high voltage buck switching regulator. The VC pin
is designed to work with the LT®3480, LT3653 and LT3505.
Consult factory for additional approved high voltage buck
regulators. See the “External HV Buck Control through the
VC Pin” section for operating information.
CLPROG (Pin 43): Input Current Program and Input
Current Monitor Pin. A resistor from CLPROG to ground
determines the upper limit of the current drawn from the
VBUS pin (i.e., the input current limit). A precise fraction
of the input current, hCLPROG, is sent to the CLPROG
pin. The input PowerPath delivers current until the
CLPROG pin reaches 2V (10x mode), 1V (5x mode) or 0.2V
(1x mode). Therefore, the current drawn from VBUS will
be limited to an amount given by hCLPROG and RCLPROG.
In USB applications the resistor RCLPROG should be set
to no less than 2.1k.
CHRG (Pin 44): Open-Drain Charge Status Output. The
CHRG pin indicates the status of the battery charger. If
CHRG is high then the charger is near the float voltage
(charge current less than 1/10th programmed charge cur-
rent) or charging is complete and charger is disabled. A low
on CHRG indicates that the charger is enabled. For more
information see the “Charge Status Indication” section.
Ground (Exposed Pad Pin 45): The exposed package pad is
ground and must be soldered to PCB ground for electrical
contact and rated thermal performance.
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