ISL6522B Datasheet, PDF (6/15 Pages) Intersil Corporation – Buck and Synchronous Rectifier Pulse-Width Modulator (PWM) Controller

ISL6522B
Functional Pin Descriptions
ISL6522B (SOIC)
TOP VIEW
RT 1
OCSET 2
SS 3
COMP 4
FB 5
EN 6
GND 7
14 _VCC
13 PVCC
12 LGATE
11 PGND
10 BOOT
9 UGATE
8 PHASE
ISL6522B (QFN)
TOP VIEW
16 15 14 13
SS 1
COMP 2
FB 3
12 PVCC
11 LGATE
10 PGND
EN 4
9 BOOT
5678
RT
This pin provides oscillator switching frequency adjustment.
By placing a resistor (R_T) from this pin to GND, the nominal
200kHz switching frequency is increased according to the
following equation:
Fs
≈
200
kH
z
+
-⁵----^•-----¹---⁰----⁶-
R_T
(R_T to GND)
Conversely, connecting a pull-up resistor (R_T) from this pin
to V_CC reduces the switching frequency according to the
following equation:
Fs
≈
200
k
H
z
–
4_-----•_-----1_---0_----⁷_-
R_T
(R_T to 12V)
OCSET
Connect a resistor (R_OCSET) from this pin to the drain of the
upper MOSFET. R_OCSET, an internal 200µA current source
(I_OCS), and the upper MOSFET on-resistance (r_DS(ON)) set
the converter overcurrent (OC) trip point according to the
following equation:
I_PEAK
=
I_{--O-----C----S-----}•_----R_{-----O----C-----S----E---T--}
r_DS(ON)
An overcurrent trip cycles the soft-start function.
SS
Connect a capacitor from this pin to ground. This capacitor,
along with an internal 10µA current source, sets the soft-start
interval of the converter.
COMP and FB
COMP and FB are the available external pins of the error
amplifier. The FB pin is the inverting input of the error
amplifier and the COMP pin is the error amplifier output.
These pins are used to compensate the voltage-control
feedback loop of the converter.
EN
This pin is the open-collector enable pin. Pull this pin below
1V to disable the converter. In shutdown, the soft-start pin is
discharged and the UGATE and LGATE pins are held low.
GND
Signal ground for the IC. All voltage levels are measured
with respect to this pin.
PHASE
Connect the PHASE pin to the upper MOSFET source. This
pin is used to monitor the voltage drop across the MOSFET
for overcurrent protection. This pin also provides the return
path for the upper gate drive.
UGATE
Connect UGATE to the upper MOSFET gate. This pin
provides the gate drive for the upper MOSFET. This pin is also
monitored by the adaptive shoot through protection circuitry to
determine when the upper MOSFET has turned off.
BOOT
This pin provides bias voltage to the upper MOSFET driver.
A bootstrap circuit may be used to create a BOOT voltage
suitable to drive a standard N-Channel MOSFET.
PGND
This is the power ground connection. Tie the lower MOSFET
source to this pin.
LGATE
Connect LGATE to the lower MOSFET gate. This pin provides
the gate drive for the lower MOSFET. This pin is also
monitored by the adaptive shoot through protection circuitry to
determine when the lower MOSFET has turned off.
PVCC
Provide a bias supply for the lower gate drive to this pin.
VCC
Provide a 12V bias supply for the chip to this pin.
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