LTC4215/LTC4215-2
8
4215fe
PIN FUNCTIONS
ADIN (QFN Package): ADC Input. A voltage between 0V
and 1.235V applied to this pin is measured by the onboard
ADC. Tie to ground if unused.
ADR0, ADR1, ADR2 (ADR1, ADR2 Available in QFN Pack-
age): Serial Bus Address Inputs. Tying these pins to ground,
to the INTV
CC
pin or open confi gures one of 27 possible
addresses. See Table 1 in Applications Information.
ALERT: Fault Alert Output. Open-drain logic output that
is pulled to ground when a fault occurs to alert the host
controller. A fault alert is enabled by the ALERT register.
See Applications Information. Tie to ground if unused.
EN (QFN Package): Enable Input. Ground this pin to
indicate a board is present and enable the N-channel
MOSFET to turn on. When this pin is high, the MOSFET
is not allowed to turn on. An internal 10µA current source
pulls up this pin. Transitions on this pin are recorded in
the Fault register. A high-to-low transition activates the
logic to read the state of the ON pin and clear Faults. See
Applications Information.
EXPOSED PAD (Pin 25, QFN Package): Exposed Pad may
be left open or connected to device ground.
FB: Foldback Current Limit and Power Good Input. A
resistive divider from the output is tied to this pin. When
the voltage at this pin drops below 1.235V, power is not
considered good. The power bad condition may result in the
GPIO pin pulling low or going high impedance depending
on the confi guration of control register bits A6 and A7.
Also a power bad fault is logged in this condition if the
LTC4215 has fi nished the start-up cycle and the GATE pin
is high. See Applications Information. The start-up current
limit folds back from a 25mV sense voltage to 10mV as
the FB pin voltage falls from 0.6V to 0V. Foldback is not
active once the part leaves start-up and the current limit
is increased to 75mV.
GATE: Gate Drive for External N-Channel MOSFET. An
internal 20µA current source charges the gate of the
MOSFET. Often no compensation capacitor is required on
the GATE pin, but a resistor and capacitor network from
this pin to ground may be used to set the turn-on output
voltage slew rate. See Applications Information. During
turn-off there is a 1mA pulldown current. During a short
circuit or undervoltage lockout (V
DD
or INTV
CC
), a 450mA
pulldown current source between GATE and SOURCE is
activated.
GND: Device Ground.
GPIO: General Purpose Input/Output. Open-drain logic
output or logic input. Defaults to an output set to pull
low to indicate power is not good. Confi gure according
to Table 2 and 3.
INTV
CC
: Low Voltage Supply Decoupling Output. Connect
a 0.1µF capacitor from this pin to ground.
ON: On Control Input. A rising edge turns on the external
N-channel MOSFET and a falling edge turns it off. This
pin also confi gures the state of the FET On bit in the con-
trol register (and hence the external MOSFET) at power
up. For example, if the ON pin is tied high, then the FET
On bit (A3 in Table 2) goes high 100ms after power-up.
Likewise if the ON pin is tied low then the part remains
off after power-up until the FET On bit is set high using
the I
2
C bus. A high-to-low transition on this pin clears
the fault register.
OV (QFN Package): Overvoltage Comparator Input. Con-
nect this pin to an external resistive divider from V
DD
. If
the voltage at this pin rises above 1.235V, an overvoltage
fault is detected and the GATE turns off. Tie to GND if
unused.
