LTC3576 Datasheet, PDF (14/48 Pages) Linear Technology – Switching Power Manager with USB On-the-Go + Triple Step-Down DC/DCs

LTC3576/LTC3576-1
PIN FUNCTIONS
DV_CC (Pin 12): Logic Supply for the I²C Serial Port. If the
serial port is not needed, it can be disabled by grounding
DV_CC. When DV_CC is grounded, the I²C bits are set to their
default values. See Table 3.
SCL (Pin 13): Clock Input Pin for the I²C Serial Port. The
I²C logic levels are scaled with respect to DV_CC. If DV_CC
is grounded, the SCL pin is equivalent to the C2, C4 and
C6 bits in the I²C serial port. SCL in conjunction with SDA
determine the operating modes of switching regulators 1,
2 and 3 when DV_CC is grounded. See Tables 3 and 5. Has
a 2μA internal pull-down current source.
SDA (Pin 14): Data Input Pin for the I²C Serial Port. The
I²C logic levels are scaled with respect to DV_CC. If DV_CC
is grounded, the SDA pin is equivalent to the C3, C5 and
C7 bits in the I²C serial port. SDA in conjunction with SCL
determine the operating modes of switching regulators 1,
2 and 3 when DV_CC is grounded. See Tables 3 and 5. Has
a 2μA internal pull-down current source.
NC (Pin 15): Unconnected Pin. This pin is not connected
internally to the part. It is permissible to tie this pin to V_IN3
in order to make the V_IN3 PCB trace wider.
V_IN3 (Pin 16): Power Input for Switching Regulator 3.
This pin will generally be connected to V_OUT. A 1μF MLCC
capacitor is recommended on this pin.
SW3 (Pin 17): Power Transmission Pin for Switching
Regulator 3.
NC (Pin 18): Unconnected Pin. This pin is not connected
internally to the part. It is permissible to tie this pin to SW3
in order to make the SW3 PCB trace wider.
EN3 (Pin 19): Logic Input. This logic input pin indepen-
dently enables switching regulator 3. Active high. This
pin is logically ORed with its corresponding bit in the
I²C serial port. See Table 3. Has a 2μA internal pull-down
current source.
FB3 (Pin 20): Feedback Input for Switching Regulator 3.
When regulator 3’s control loop is complete, this pin servos
to 1 of 16 possible set points based on the commanded
value from the I²C serial port. See Table 4.
RST3 (Pin 21): Logic Output. This in an open-drain output
which indicates that switching regulator 3 has settled to
its final value. It can be used as a power-on reset for the
primary microprocessor or to enable the other switching
regulators for supply sequencing.
EN2 (Pin 22): Logic Input. This logic input pin indepen-
dently enables switching regulator 2. Active high. This
pin is logically ORed with its corresponding bit in the
I²C serial port. See Table 3. Has a 2μA internal pull-down
current source.
SW2 (Pin 23): Power Transmission Pin for Switching
Regulator 2.
V_IN2 (Pin 24): Power Input for Switching Regulator 2.
This pin will generally be connected to V_OUT. A 1μF MLCC
capacitor is recommended on this pin.
FB2 (Pin 25): Feedback Input for Switching Regulator 2.
When regulator 2’s control loop is complete, this pin servos
to 1 of 16 possible set points based on the commanded
value from the I²C serial port. See Table 4.
V_C (Pin 26): Bat-Track External Switching Regulator Control
Output. This pin drives the V_C pin of an external Linear
Technology step-down switching regulator. An external P-
channel MOSFET is sometimes required to provide power
to V_OUT with its gate tied to the ACPR pin (see Applications
Information). In concert with WALL and ACPR, it will
regulate V_OUT to maximize battery charger efficiency
WALL (Pin 27): External Power Source Sense Input. WALL
should be connected to the output of the external high
voltage switching regulator and to the drain of an external
P-channel MOSFET if used. It is used to determine when
power is applied to the external regulator. When power
is detected, ACPR is driven low and the USB input is au-
tomatically disabled. Pulling this pin above 4.3V enables
the V_C pin.
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