ISL6540_06 Datasheet, PDF (10/20 Pages) Intersil Corporation – Single-Phase Buck PWM Controller with Integrated High Speed MOSFET Driver and Pre-Biased Load Capability

ISL6540
LIN_DRV (Pin 15, External Linear Regulator Drive)
This pin allows the use of an external pass element to power
the IC for input voltages above 5.0V. It should be connected
to GND when using an external 5V supply or the internal
linear regulator. When using the external linear regulator
option, this pin should be connected to the gate of a PMOS
pass element, a pull up resistor must be connected between
the PMOS device’s gate and source for proper operation.
PVCC (Pin 16, Driver Bias Voltage)
This pin is the output of the internal series linear regulator. It
also provides the bias for both low side and high side
MOSFET drivers. The maximum voltage differential between
PVCC and PGND is 6V. Its recommended operational
voltage range is 2.9V to 5.6V. At minimum a 10µF capacitor
is required for decoupeing PVCC to PGND. For proper
operation the PVCC capacitor must be within 150mils of the
PVCC and the PGND pins and must be connected to these
pins with dedicated traces.
LGATE (Pin 17)
This pin provides the drive for the low side MOSFET and
should be connected to its gate.
PGND (Pin 18, Power Ground)
This pin connects to the low side MOSFET's source and
provides the ground return path for the lower MOSFET
driver and internal power circuitries. In addition, PGND is the
return path for the low side MOSFET’s r_DS(ON) current
sensing circuit.
PHASE (Pin 19)
This pin connects to the source of the high side MOSFET
and the drain of the low side MOSFET. This pin represents
the return path for the high side gate driver. During normal
switching, this pin is used for high side and low side current
sensing.
UGATE (Pin 20)
This pin provides the drive for the high side MOSFET and
should be connected to its gate.
BOOT (Pin 21)
This pin provides the bootstrap bias for the high side driver.
The absolute maximum voltage differential between BOOT
and PHASE is 6.0V (including the voltage added due to the
overcharging of the bootstrap capacitor); its operational
voltage range is 2.5V to 5.6V with respect to PHASE. It is
recomended that a 2.2Ω resistor be placed in series with the
bootstrap diode to prevent over chargeing of the BOOT
capacitor during normal operation.
HSOC (Pin 22)
The high side sourcing current limit is set by connecting this
pin with a resistor and capacitor to the drain of the high side
MOSEFT. A 100µA current source develops a voltage
across the resistor which is then compared with the voltage
developed across the high side MOSFET. An initial ~120ns
blanking period is used to eliminate sampling error due to
the switching noise before the current is measured.
LSOC (Pin 23)
The low side source and sinking current limit is set by
placing a resistor (R_LSOC ) and capacitor between this pin
and PGND. A 100µA current source develops a voltage
across R_LSOC which is then compared with the voltage
developed across the low side MOSFET when on. The
sinking current limit is set at 1x of the nominal sourcing limit
in ISL6540. An initial ~120ns blanking period is used to
eliminate the sampling error due to switching noise before
the current is measured.
FS (Pin 24)
This pin provides oscillator switching frequency adjustment
by placing a resistor (R_FS) from this pin to GND.
COMP (Pin 25)
This pin is the error amplifier output. It should be connected
to the FB pin through the desired compensation network.
FB (Pin 26)
This pin is the inverting input of the error amplifier and has a
maximum usable voltage of VCC-1.8V. When using the
internal differential remote sense functionality, this pin
should be connected to VMON by a standard feedback
network. In the event the remote sense buffer is disabled,
the VMON pin should be connected to VOUT by a resistor
divider along with FB’s compensation network.
GND (Pin 27, Analog Ground)
Signal ground for the IC. All voltage levels are measured
with respect to this pin. This pin should not be left floating.
VMON (Pin 28)
This pin is the output of the differential remote sense
instrumentation amplifier. It is connected internally to the
OV/UV/POOD comparators. The VMON pin should be
connected to the FB pin by a standard feedback network. In
the event of the remote sense buffer is disabled, the VMON
pin should be connected to VOUT by a resistor divider along
with FB’s compensation network. An RC filter should be
used if VMON is to be connected directly to FB instead of to
VOUT through a separate resistor divider network.
GND (Bottom Side Pad, Analog Ground)
Signal ground for the IC. All voltage levels are measured
with respect to this pin. This pin should not be left floating.
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FN9214.0
March 9, 2006