Datasheet

LTC4155
12
4155fc
PIN FUNCTIONS
SDA (Pin 1): Data Input/Output for the I
2
C Serial Port.
The I
2
C input levels are scaled with respect to DVCC for
I
2
C compliance.
DVCC (Pin 2): Logic Supply for the I
2
C Serial Port. DVCC
sets the reference level of the SDA and SCL pins for I
2
C
compliance. It should be connected to the same power
supply used to power the I
2
C pull-up resistors.
IRQ (Pin 3): Open-Drain Interrupt Output. The IRQ pin
can be used to generate an interrupt due to a variety of
maskable status change events within the LTC4155.
ID (Pin 4): USB A-Device Detection Pin. When wired to a
mini- or micro-USB connector, the ID pin detects when
the “A” side of a mini or micro-USB cable is connected
to the product. If the ID pin is pulled down, and the
LOCKOUT_ID_PIN bit is not set in the I
2
C port, the switch-
ing PowerPath operates in reverse providing USB power
to the V
BUS
pin from the battery. USB On-The-Go power
can only be delivered from the USB multiplexer path.
CLPROG1 (Pin 5): Primary V
BUS
Current Limit Program-
ming Pin. A resistor from CLPROG1 to ground determines
the upper limit of the current drawn from the V
BUS
pin when
CLPROG1 is selected. A precise measure of V
BUS
current,
h
CLPROG1
–1
, is sent to the CLPROG1 pin. The switching
regulator increases power delivery until CLPROG1 reaches
1.2V. Therefore, the current drawn from V
BUS
will be
limited to an amount given by the 1.2V reference voltage,
h
CLPROG1
and R
CLPROG1
.
Typically CLPROG1 is used to override the USB compliant
input current control pin, CLPROG2, in applications where
USB compliance is not a requirement. This would be use-
ful for applications that use a dedicated wall adapter and
would rather not be limited to the 500mW start-up value
required by USB specifications. If USB compliance is a
requirement at start-up, CLPROG1 should be connected
to CLPROG2 and a single resistor should be used. See
the CLPROG2 pin description.
In USB noncompliant designs, the user is encouraged to
use an R
CLPROG1
value that best suits their application
for start-up current limit. See the Operation section for
more details.
CLPROG2 (Pin 6): Secondary V
BUS
Current Limit Pro-
gram Pin. CLPROG2 controls the V
BUS
current limit when
either selected via I
2
C command or when CLPROG1 and
CLPROG2 are shorted together. When selected, a resistor
from CLPROG2 to ground determines the upper limit of
the current drawn from the V
BUS
pin. Like CLPROG1, a
precise fraction of V
BUS
current, h
CLPROG2
–1
, is sent to the
CLPROG2 pin. The switching regulator increases power
delivery until CLPROG2 reaches 1.2V. Therefore, the cur-
rent drawn from V
BUS
will be limited to an amount given
by the 1.2V reference voltage, h
CLPROG2
and R
CLPROG2
.
There are a multitude of ratios for h
CLPROG2
available by I
2
C
control, three of which correspond to the 100mA, 500mA
and 900mA USB specifications. CLPROG2 is also used to
regulate maximum input current in the USB suspend mode
and maximum output current in USB On-The-Go mode.
If CLPROG1 and CLPROG2 are shorted together at the onset
of available input power, the LTC4155 selects CLPROG2 in
the 100mA USB mode to limit input current. This ensures
USB compliance if so desired. For USB compliance in all
modes, the user is encouraged to make R
CLPROG2
equal
to the value declared in the Electrical Characteristics.
WALLSNS (Pin 7): Highest Priority Multiplexer Input and
Overvoltage Protection Sense Input. WALLSNS should be
connected through a 3.6k resistor to a high priority input
power connector and one drain of two source-connected
N-channel MOSFET pass transistors. When voltage is
detected on WALLSNS, it draws a small amount of current
to power a charge pump which then provides gate drive to
WALLGT to energize the external transistors. If the input
voltage exceeds V
OVLO
, WALLGT will be pulled to GND
to disable the pass transistors and protect the LTC4155
from high voltage.
USBSNS (Pin 8): Lowest Priority Multiplexer Input and
Overvoltage Protection Sense Input. USBSNS should be
connected through a 3.6k resistor to a low priority input
power connector and one drain of two source-connected
N-channel MOSFET pass transistors. When voltage is
detected on USBSNS, and no voltage is detected on
WALLSNS, USBSNS draws a small amount of current to
power a charge pump which then provides gate drive to