LTC3566-2_15 Datasheet, PDF (10/28 Pages) Linear Technology – High Efficiency USB Power Manager Plus 1A Buck-Boost Converter

LTC3566/LTC3566-2
PIN FUNCTIONS
SWCD1 (Pin 11): Switch Node for the (Buck-Boost)
Switching Regulator. Connected to internal power switches
C and D. External inductor connects between this node
and SWAB1.
ILIM0 (Pin 13): Logic Input. Control pin for ILIM0 bit of
the current limit of the PowerPath switching regulator.
See Table 2. Active high. Has a 1.6μA internal pull-down
current source.
ILIM1 (Pin 14): Logic Input. Control pin for ILIM1 bit of
the current limit of the PowerPath switching regulator.
See Table 2. Active high. Has a 1.6μA internal pull-down
current source.
PROG (Pin 15): Charge Current Program and Charge
Current Monitor Pin. Connecting a resistor from PROG
to ground programs the charge current. If sufficient in-
put power is available in constant-current mode, this pin
servos to 1V. The voltage on this pin always represents
the actual charge current.
CHRG (Pin 16): Open-Drain Charge Status Output. The
CHRG pin indicates the status of the battery charger. Four
possible states are represented by CHRG: charging, not
charging, unresponsive battery and battery temperature
out of range. CHRG is modulated at 35kHz and switches
between a low and high duty cycle for easy recognition
by either humans or microprocessors. See Table 1. CHRG
requires a pull-up resistor and/or LED to provide indica-
tion.
GND (Pin 17): GND pin for USB Power Manager.
GATE (Pin 18): Analog Output. This pin controls the gate
of an optional external P-channel MOSFET transistor used
to supplement the ideal diode between V_OUT and BAT. The
external ideal diode operates in parallel with the internal
ideal diode. The source of the P-channel MOSFET should
be connected to V_OUT and the drain should be connected
to BAT. If the external ideal diode FET is not used, GATE
should be left floating.
BAT (Pin 19): Single-Cell Li-Ion Battery Pin. Depending on
available V_BUS power, a Li-Ion battery on BAT will either
deliver power to V_OUT through the ideal diode or be charged
from V_OUT via the battery charger.
V_OUT (Pin 20): Output Voltage of the Switching PowerPath
Controller and Input Voltage of the Battery Charger. The
majority of the portable product should be powered from
V_OUT. The LTC3566 family will partition the available power
between the external load on V_OUT and the internal battery
charger. Priority is given to the external load and any extra
power is used to charge the battery. An ideal diode from
BAT to V_OUT ensures that V_OUT is powered even if the load
exceeds the allotted power from V_BUS or if the V_BUS power
source is removed. V_OUT should be bypassed with a low
impedance ceramic capacitor.
V_BUS (Pin 21): Primary Input Power Pin. This pin delivers
power to V_OUT via the SW pin by drawing controlled current
from a DC source such as a USB port or wall adapter.
SW (Pin 22): Power Transmission Pin for the USB Pow-
erPath. The SW pin delivers power from V_BUS to V_OUT
via the step-down switching regulator. A 3.3μH inductor
should be connected from SW to V_OUT.
CHRGEN (Pin 23): Logic Input. This logic input pin inde-
pendently enables the battery charger. Active low. Has a
1.6μA internal pull-down current source.
EN1 (Pin 24): Logic Input. This logic input pin independently
enables the buck-boost switching regulator. Active high.
Has a 1.6μA internal pull-down current source.
Exposed Pad (Pin 25): Ground. Buck-boost logic and USB
Power Manager ground connections. The Exposed Pad
should be connected to a continuous ground plane on the
printed circuit board directly under the LTC3566.
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