
5
FN9049.7
December 28, 2004
Functional Pin Description
GND (Pin 1)
Signal ground for the IC.
LGATE1, LGATE2 (Pin 2, 27)
These are outputs of the lower MOSFET drivers.
PGND1, PGND2 (Pin 3, 26)
These pins provide the return connection for lower gate 
drivers. These pins are connected to sources of the lower 
MOSFETs of their respective converters.
PHASE1, PHASE2 (Pin 4, 25)
The PHASE1 and PHASE2 points are the junction points of 
the upper MOSFET sources, output filter inductors, and 
lower MOSFET drains. Connect these pins to the respective 
converter’s upper MOSFET source.
UGATE1, UGATE2 (Pin 5, 24)
These pins provide the gate drive for the upper MOSFETs.
BOOT1, BOOT2 (Pin 6, 23)
These pins power the upper MOSFET drivers of the PWM 
converter. Connect this pin to the junction of the bootstrap 
capacitor with the cathode of the bootstrap diode. Anode of 
the bootstrap diode is connected to the VCC pin.
ISEN1, ISEN2 (Pin 7, 22)
These pins are used to monitor the voltage drop across the 
lower MOSFET for current feedback and overcurrent 
protection. For precise current detection these inputs can be 
connected to the optional current sense resistors placed in 
series with the source of the lower MOSFETs.
EN1, EN2 (Pin 8, 21)
These pins enable operation of the respective converter 
when high. When both pins are low, the chip is disabled and 
only low leakage current <1
μ
A is taken from V
CC
 and V
IN
. 
These pins are to be connected together and switched at the 
same time.
VOUT1, VOUT2 (Pin 9, 20)
These pins when connected to the converters’ respective 
outputs provide the output voltage inside the chip to reduce 
output voltage excursion during HYS/PWM transition. When 
connected to ground, these pins command forced 
converters operate in continuous conduction mode at all 
load levels.
VSEN1, VSEN2 (Pin 10, 19)
These pins are connected to the resistive dividers that set 
the desired output voltage. The PGOOD, UVP, and OVP 
circuits use this signal to report output voltage status.
OCSET1 (Pin 11)
A resistor from this pin to ground sets the overcurrent 
threshold for the first controller.
SOFT1, SOFT2 (Pin 12, 17)
These pins provide soft-start function for their respective 
controllers. When the chip is enabled, the regulated 5
μ
A 
pull-up current source charges the capacitor connected from 
the pin to ground. The output voltage of the converter follows 
the ramping voltage on the SOFT pin. 
DDR (Pin 13)
This pin, when high, transforms dual channel chip into 
complete DDR memory solution. The OCSET2 pin becomes 
an input to provide the required tracking function. The 
channel synchronization is changed from out-of-phase to in-
phase. The PG2/REF pin becomes the output of the VDDQ/
2 buffered voltage that is used as a reference voltage by the 
second channel.
VIN (Pin 14)
Provides battery voltage to the oscillator for feed-forward 
rejection of the input voltage variation. 
When connected to ground via 100k
 resistor while the 
DDR pin is high, this pin commands the out-of-phase 90
o 
channels synchronization for reduced inter-channel 
interference.
PG1 (Pin 15)
PGOOD1 is an open drain output used to indicate the status 
of the output voltage. This pin is pulled low when the first 
channel output is not within
±10% of the set value. 
PG2/REF (Pin 16)
This pin has a double function depending on the mode the 
chip is operating. When the chip is used as a dual channel 
PWM controller (DDR = 0), the pin provides a PGOOD2 
function for the second channel. The pin is pulled low when 
the second channel output is not within
±10% of the set value.
In DDR mode (DDR = 1), this pin serves as an output of the 
buffer amplifier that provides VDDQ/2 reference voltage 
applied to the OCSET2 pin.
OCSET2 (Pin 18)
In a dual channel application (DDR = 0), a resistor from this 
pin to ground sets the overcurrent threshold for the second 
controller. 
In the DDR application (DDR = 1), this pin sets the output 
voltage of the buffer amplifier and the second controller and 
should be connected to the center point of a divider from the 
VDDQ output.
VCC (Pin 28)
This pin powers the controller.
ISL6225