?/DIV>
T output
of an external supply monitor or power good output of a
DC/DC converter. When all supplies have been turned on,
a timing cycle is started at the end of which the PGI pin is
sampled. If it is low, all external MOSFETs are shut off. If
the PGI Disable control bit C3 is not set, pulling this pin
low for more than 20約 during normal operation will also
shut off all MOSFETs. Tie to INTV
CC
if unused.
PRECHARGE: Bus Precharge Output. This pin can source
70mA at 1V as soon as 3V
IN
is powered-up. Leave it open
if unused.
SCL: Serial Bus Clock Input. Data at the SDA pin is shifted
in or out on rising edges of SCL. This is a high impedance
pin that is generally driven by an open-collector output
from a master controller.
SDA: Serial Bus Data Input and Output. This is a high
impedance input when address, command or data bits
are shifted in. It is an open-drain output when sending
data back to the master controller or acknowledging a
write operation. An external pull-up resistor or current
source is required.
SS: Soft-Start Input. Connect a capacitor between this pin
and ground to set the rate of increase of current limit during
start-up for dI/dt limited inrush current. When an external
MOSFET is turned on, a 20糀 pull-up current charges the
capacitor. The voltage ramp on the capacitor is converted
into an internal current limit increasing linearly with time.
Leave it open if dI/dt limited inrush is not required.
TIMER: Timer Input. A capacitor between this pin and
ground sets the duration of the start-up, PGI and auto-retry
timing cycles to be 23.3ms/糉, 233ms/糉 and 1.17s/糉
respectively. A timing cycle consists of TIMER being
charged to 2.56V with an internal pull-up current source
and then being reset by a switch to ground. The timing
cycle ends when TIMER falls below 0.23V. The start-up,
PGI and auto-retry timing cycles use 100糀, 10糀 and
2糀 pull-up current sources respectively.
V
EEGATE
: Gate Drive for 12V Supply External N-Chan-
nel MOSFET. An internal 20糀 current source charges
the gate of the external N-channel MOSFET. An internal
clamp limits the gate voltage to 6.2V above V
EEIN
. During
turn-off, a 3.5mA pull-down current discharges V
EEGATE
to V
EEIN
. During short-circuit a 65mA pull-down current
between V
EEGATE
and V
EEIN
is activated. If a 12V supply
is not available, connect V
EEGATE
to ground and use the
CFG pin appropriately.
V
EEIN
: 12V Supply, Current Sense and ADC Input. An
undervoltage lockout circuit, with 38mV hysteresis, pre-
vents any external MOSFET from turning on when this
pin is above 10.5V. The V
EEIN
undervoltage lockout can
be disabled by using the CFG pin. If a 12V supply is not
available, connect V
EEIN
to ground and use the CFG pin
appropriately.
V
EEOUT
: 12V Supply Foldback, ADC and Power Bad Input.
Connect this pin to the drain of the 12V supply external
N-channel MOSFET switch. Power is considered bad if this
pin rises above 11.1V. The comparator on this pin has a
built-in hysteresis of 54mV. The V
EEOUT
power bad function
can be disabled by using the CFG pin. This pin is also an
input to the ADC and the current limit foldback circuit. A
1800?active pull-up discharges V
EEOUT
to ground when
the external MOSFET is turned off. If a 12V supply is not
available, connect V
EEOUT
to ground and use the CFG pin
appropriately.
V
EESENSE
: 12V Supply Current Sense and ADC Input.
Connect this pin to the output of the 12V current sense
resistor. The current limit circuit controls the V
EEGATE
pin
to limit the sense voltage between the V
EESENSE
and V
EEIN
pins to 50mV or less during start-up and 150mV thereafter.
During start-up a foldback feature lowers the current limit
to 16mV as the V
EEOUT
pin approaches ground. A circuit
breaker, enabled after start-up, trips when the sense voltage
exceeds 50mV for 22約. To disable current limit, connect
this pin to V
EEIN
. If a 12V supply is not available, connect
V
EESENSE
to ground and use the CFG pin appropriately.