isl8120 Intersil Corporation, isl8120 Datasheet - Page 19

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

standard feedback network when both channels operating
independently. When VSEN1-, 2- are pulled within 700mV of
VCC, the corresponding differential amplifier is disabled and
its output (VMON pin) is high impedance. In such an event,
the VMON pin can be used as an additional monitor of the
output voltage with a resistor divider to protect the system
against single point of failure, which occurs in the system
using the same resistor divider for both of the UV/OV
comparator and output voltage feedback.
Modes of Operation
There are 9 typical operation modes depending upon the
signal levels on EN1/FF1, EN2/FF2, VSEN2+, VSEN2-, FB2,
and CLKOUT/REFIN.
MODE 1: The IC is completely disabled when EN1/FF1 and
EN2/FF2 are pulled below 0.8V.
MODE 2: With EN1/FF1 pulled low and EN2/FF2 pulled high
(Mode 2A), or EN1/FF1 pulled high and EN2/FF2 pulled low
(Mode 2B), the ISL8120 operates as a single phase
regulator. the current sourcing out from the ISHARE pin
represents the first channel current plus 15µA offset current.
MODE 3: When VSEN2- is used as a negative sense line,
both channels’ phase shift depends upon the voltage level of
CLKOUT/REFIN. When the CLKOUT/REFIN pin is within
29% to 45% of VCC, Channel 2 delays 0° over Channel 1
(Mode 3A); when within 45% to 62% of VCC, 90°delay
(Mode 3B); when greater than 62% to VCC, 180° delay
(Mode 3C). Refer to the “DDR and Dual Mode Operation” on
page 30.
MODE 4: When VSEN2- is used as a negative remote sense
line, and CLKOUT/REFIN is connected to a external voltage
ramp lower than the internal soft-start ramp and lower than
0.6V, the external ramp signal will replaces Channel 2’s
internal soft-start ramp to be tracked at startup, controller
operating in DDR mode. The controller will use the lowest
voltage among the internal 0.6V reference, the external
voltage in CLKOUT/REFIN pin and the soft-start ramp signal.
Channel 1 is delayed 60° behind Channel 2. Refer to the
“DDR and Dual Mode Operation” on page 30.
MODE 5: With VSEN2- pulled within 700mV of VCC and
FB2 pulled to ground, the internal channels are 180°
out-of-phase and operate in 2-phase single output mode
(5A). The CLKOUT/REFIN pin (rising edge) also signals out
clock with 60° phase shift relative to the Channel 1’s clock
signal (falling edge of PWM) for 6-phase operation with two
other ISL8120s (5B). When the share Pins are not
connected to each other for the three ICs in sync, two of
which can operate in Mode 5A (3 independent outputs can
be generated (Mode 5D)) and Modes 3 and 4 (to generate 4
independent outputs (Mode 5C)) respectively.
MODE 6: With VSEN2- pulled within 700mV of VCC, FB2
pulled high and VSEN2+ pulled low, the internal channels
(as 1
st
and 3
rd
Phase, respectively) are 240° out-of-phase
19
ISL8120
and operate in 3-phase single output mode, combined with
another ISL8120 at MODE 2B. The CLKOUT/REFIN pin
signals out 120° relative phases to the falling edge of
Channel 1’s clock signal to synchronize with the second
ISL8120’s Channel 1 (as 2
MODE 7: With VSEN2- pulled within 700mV of VCC and
FB2 and VSEN2+ pulled high, the internal channels is 180°
out-of-phase. The CLKOUT/REFIN pin (rising edge) signals
out 90° relative phase to the Channel 1’s clock signal (falling
edge of PWM) to synchronize with another ISL8120, which
can operate at Mode 3, 4, 5A, or 7A. A 4-phase single output
converter can be constructed with two ISL8120s operating in
Mode 5A or 7A (Mode 7A). If the share bus is not connected
between ICs, each IC could generate an independent output
(Mode 7B). When the second ISL8120 operates as two
independent regulators (Mode 3) or in DDR mode (Mode 4),
then three independent output system is generated (Mode
7C). Both ICs can also be constructed as a 3-phase
converter (0°, 90°, and 180°, not a equal phase shift for
3-phase) with a single phase regulator (270°).
MODE 8: The output CLKOUT signal allows expansion for
12-phase operation with the cascaded sequencing as shown
in Table 1. No external clock is required in this mode for the
desired phase shift.
MODE 9: With an external clock, the part can be expanded
for 5, 7, 8, 9 10 and 11 phase single output operation with the
desired phase shift.
nd
Phase).
March 28, 2008
FN6641.0