4
FN9027.13
August 28, 2015
Functional Pin Description
NOTE: Pin numbers refer to the SOIC package. Check PINOUT
diagrams for QFN pin numbers.
VCC (Pin 1)
Supplies all the power necessary to operate the chip. The IC
starts to operate when the voltage on this pin exceeds the
rising POR threshold and shuts down when the voltage on
this pin drops below the falling POR threshold. Connect this
pin to a 5V (±5%) supply.
PGOOD (Pin 2)
Power good is an open drain output used to indicate the
status of the output voltage. This pin is pulled low when the
converter output voltage is either 10% below or 15% above
the reference voltage.
COMP (Pin 3)
Output of the internal error amplifier. Connect this pin to the
external feedback compensation network.
DROOP (Pin 4)
Output voltage droop or active voltage positioning is
provided by connecting this pin to the FB pin. An internal
current source creates the droop across an external
feedback resistor, R
FB
. If no droop is desired, this pin MUST
be left open.
FB (Pin 5)
The FB pin is the inverting input of the internal error
amplifier. Connect this pin to the external feedback
compensation network and a resistor divider from the output
for proper control and protection of converter load.
VSEN (Pin 6)
This pin is connected through a resistor divider to the
converter’s output voltage to provide remote sensing. The
undervoltage and overvoltage protection comparators trigger
off this input.
FS/EN (Pin 7)
Connecting a resistor from this pin to ground sets the
internal oscillator frequency. The switching frequency, F
SW
,
of the converter is adjustable between 80kHz and 1.5MHz.
Pulling this pin to ground disables the converter and three-
states the PWM outputs.
GND (Pin 8)
Bias and reference ground for all controller signals.
PWM1 (Pin 13), PWM2 (Pin 12), PWM3 (Pin 9),
PWM4 (Pin 16)
The controller PWM drive signals are connected to the
individual HIP660x driver PWM input pins. The number of
active channels is determined by the state of PWM3 and
PWM4. If PWM3 is tied to VCC, this indicates to the
controller that two channel operation is desired. In this case,
PWM4 should be left open or tied to VCC. Tying PWM4 to
VCC indicates that three channel operation is desired.
ISEN1 (Pin 14), ISEN2 (Pin 11), ISEN3 (Pin 10),
ISEN4 (Pin 15)
These pins are used to monitor the voltage drop across the
lower MOSFETs for current feedback, output voltage droop
and overcurrent protection. A resistor must be placed in
series with each of these inputs and their respective PHASE
node. The resistor is sized such that the current feedback is
50A at full load. Sense lines corresponding to inactive
channels should be left open. Inactive channels are those in
which the PWM pin has been tied to VCC or left open.
Thermal Pad (in QFN only)
In the QFN package, the pad underneath the center of the
IC is a thermal substrate. The PCB “thermal land” design
for this exposed die pad should include thermal vias that
drop down and connect to one or more buried copper
plane(s). This combination of vias for vertical heat escape
and buried planes for heat spreading allows the QFN to
achieve its full thermal potential. This pad should be either
grounded or floating, and it should not be connected to
other nodes. Refer to TB389 for design guidelines.
ISL6558
