isl8120 Intersil Corporation, isl8120 Datasheet - Page 17

• Manufacturer Part Number: isl8120
• Description: Dual/n-phase Buck Pwm Controller With Integrated Drivers
• Manufacturer: Intersil Corporation

Functional Pin Description‘
GND (Pin 33, Signal and Power Ground Pad)
All voltage levels are referenced to this pad.This pad
provides a return path for the low-side MOSFET drives and
internal power circuitries as well as all analog signals.
Connect this pad to the circuit ground using the shortest
possible path (more than 5 to 6 via to the internal ground
plane, placed on the soldering pad are recommended).
VIN (Pin 16, Internal Linear Regulator Input)
This pin should be tied directly to the input rail when using
the internal linear regulator. It provides power to the internal
linear drive circuitry. When used with an external 5V supply,
this pin should be tied directly to PVCC. The internal linear
device is protected against reverse bias generated by the
remaining charge of the decoupling capacitor at PVCC when
losing the input rail.
VCC (Pin 26, Analog Circuit Bias)
This pin provides power for the analog circuitry. A RC filter is
recommended between the connection of this pin to a 2.97V
to 5.6V bias (typically PVCC). R is suggested to be a 5ohm
resistor. And in 3.3V applications, the R could be shorted to
allow the low end input in concerns of the VCC falling
threshold. The Vcc decoupling cap C is strongly
recommended to be as large as 10µF ceramic cap. This pin
can be powered either by the internal linear regulator or by
an external voltage source.
BOOT1, 2 (Pins 25, 17)
This pin provides the bootstrap bias for the high-side driver.
Internal bootstrap diodes connected to the PVCC pin provide
the necessary bootstrap charge. Its typical operational
voltage range is 2.5V to 5.6V.
UGATE1, 2 (Pin 24, 8)
These pins provide the drive for the high-side devices and
should be connected to the MOSFETs’ gates.
PHASE1, 2 (Pins 23,19)
Connect these pins to the source of the high-side MOSFETs
and the drain of the low-side MOSFETs. These pins
represent the return path for the high-side gate drives.
PVCC (Pin 12, Driver Bias Voltage)
This pin is the output of the internal series linear regulator. It
provides the bias for both low-side and high-side drives. Its
operational voltage range is 2.97V to 5.6V.
LGATE1, 2 (Pins 22, 20)
These pins provide the drive for the low-side devices and
should be connected to the MOSFETs’ gates.
FSYNC (Pin 5)
The oscillator switching frequency is adjusted by placing a
resistor (R
will lock to an external frequency source if this pin is
FS
) from this pin to GND. The internal oscillator
17
ISL8120
connected to a switching square pulse waveform, typically
the CLKOUT input signal from another ISL8120 or an
external clock. The internal oscillator synchronizes with the
leading edge of the input signal.
EN/FF1, 2 (Pins 4, 6)
These are triple function pins. The input voltages to these
pins are compared with a precision 0.8V reference and
enable their digital soft-starts. By pulling this pin to voltage
lower than the threshold, the corresponding channel can be
disabled independently. Connecting these pins to input bus
through a voltage resistor divider can monitor the input
voltage. The undervoltage lockout and its hysteresis levels
can be programmed by setting the values of the resistor
dividers. The voltages on these pins are also fed into
controller to be used to adjust the amplitude of each
individual sawtooth independently.
Furthermore, during fault (such as overvoltage, overcurrent,
and over-temperature) conditions, these pins (EN/FF_) are
used to communicate the information to other cascaded ICs
by pulling low.
PGOOD (Pin 8)
Provides an open drain Power-Good signal when both
channels are within 9% of nominal output regulation point
with 4% hysteresis (13%/9%) and soft-start is complete.
PGOOD monitors the outputs (VMON1/2) of the internal
differential amplifiers.
ISEN1A, 2A (Pins 27, 15)
These pins are the positive inputs of the current sensing
amplifier. Together with ISEN1B,2B, these pins provide
r
ISEN1B, 2B (Pins 28, 14)
These pins are the negative inputs of the current sensing
amplifier. Together with the ISEN1A, 2A pins they provide
r
“Typical Application III (2-Phase Operation with r
Sensing and Voltage Trimming)” on page 7 for r
sensing set up and “Typical Application V (4 Phase
Operation with DCR Sensing)” on page 9 for DCR sensing
set up.
ISET (Pin 2)
This pin sources an 15µA offset current plus the average
current of both channels in multiphase mode or only
Channel 1’s current in independent mode. The voltage
(V
average current level of the local active channel(s). V
compared with a 1V threshold for average overcurrent
protections. For full-scale current, R
1V/120µA = 8.33kΩ. Typically 10kΩ is used for R
ISHARE (Pin 3)
This pin is used for current sharing purposes and is
configured to current share bus representing all modules’
DS(ON)
DS(ON)
ISET
) set by an external resistor (R
, DCR, or precision resistor current sensing.
, DCR, or precision resistor current sensing. Refer to
ISET
ISET
should be
) represents the
DS(ON)
DS(ON)
SET
March 28, 2008
.
ISET
FN6641.0
is