ISL6269B
3
FN6280.3
November 17, 2014
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Functional Pin Descriptions
GND (Bottom Pad)
Signal common of the IC. Unless otherwise stated, signals are
referenced to the GND pin, not the PGND pin.
VIN (Pin 1)
The VIN pin measures the converter input voltage which is a
required input to the R3™ PWM modulator. Connect across the
drain of the high-side MOSFET to the GND pin.
VCC (Pin 2)
The VCC pin is the input bias voltage for the IC. Connect +5V from
the VCC pin to the GND pin. Decouple with at least 1µF of a MLCC
capacitor from the VCC pin to the GND pin.
FCCM (Pin 3)
The FCCM pin configures the controller to operate in Forced
Continuous Conduction Mode (FCCM) or Diode Emulation Mode
(DEM.) DEM is disabled when the FCCM pin is pulled above the
rising threshold voltage V
FCCMTHR
, conversely DEM is enabled
when the FCCM pin is pulled below the falling threshold voltage
V
FCCMTHF.
EN (Pin 4)
The EN pin is the on/off switch of the IC. The soft-start sequence
begins when the EN pin is pulled above the rising threshold
voltage V
ENTHR
and V
VCC
is above the power-on reset (POR) rising
threshold voltage
V
VCC_THR
. When the EN pin is pulled below the
falling threshold voltage V
ENTHF
PWM immediately stops.
COMP (Pin 5)
The COMP pin is the output of the control-loop error amplifier.
Compensation components for the control-loop connect across
the COMP and FB pins.
FB (Pin 6)
The FB pin is the inverting input of the control-loop error
amplifier. The converter output voltage regulates to 600mV from
the FB pin to the GND pin. Program the desired output voltage
with a resistor network connected across the VO, FB and GND
pins. Select the resistor values such that FB to GND is 600mV
when the converter output voltage is at the programmed
regulation value.
FSET (Pin 7)
The FSET pin programs the PWM switching frequency. Program
the desired PWM frequency with a resistor and a capacitor
connected across the FSET and GND pins.
VO (Pin 8)
The VO pin measures the converter output voltage and is used
exclusively as an input to the R3™ PWM modulator. Connect at
the physical location where the best output voltage regulation is
desired.
ISEN (Pin 9)
The ISEN pin programs the threshold of the OCP overcurrent fault
protection. Program the desired OCP threshold with a resistor
connected across the ISEN and PHASE pins. The OCP threshold is
programmed to detect the peak current of the output inductor.
The peak current is the sum of the DC and AC components of the
inductor current.
PGND (Pin 10)
The PGND pin conducts the turn-off transient current through the
LG gate driver. The PGND pin must be connected to complete the
pull-down circuit of the LG gate driver. The PGND pin should be
connected to the source of the low-side MOSFET through a low
impedance path, preferably in parallel with the trace connecting
the LG pin to the gate of the low-side MOSFET. The adaptive
shoot-through protection circuit, measures the low-side MOSFET
gate-source voltage from the LG pin to the PGND pin.
LG (Pin 11)
The LG pin is the output of the low-side MOSFET gate driver.
Connect to the gate of the low-side MOSFET.
PVCC (Pin 12)
The PVCC pin is the input voltage bias for the LG low-side
MOSFET gate driver. Connect +5V from the PVCC pin to the PGND
pin. Decouple with at least 1µF of an MLCC capacitor across the
PVCC and PGND pins.
BOOT (Pin 13)
The BOOT pin stores the input voltage for the UG high-side
MOSFET gate driver. Connect an MLCC capacitor across the BOOT
and PHASE pins. The boot capacitor is charged through an
internal boot diode connected from the PVCC pin to the BOOT pin,
each time the PHASE pin drops below PVCC minus the voltage
dropped across the internal boot diode.
UG (Pin 14)
The UG pin is the output of the high-side MOSFET gate driver.
Connect to the gate of the high-side MOSFET.
PHASE (Pin 15)
The PHASE pin detects the voltage polarity of the PHASE node
and is also the current return path for the UG high-side MOSFET
gate driver. Connect the PHASE pin to the node consisting of the
high-side MOSFET source, the low-side MOSFET drain and the
output inductor.
PGOOD (Pin 16)
The PGOOD pin is an open-drain output that indicates when the
converter is able to supply regulated voltage. Connect the PGOOD
pin to +5V through a pull-up resistor.
