ISL6522A Intersil Corporation, ISL6522A Datasheet - Page 4

• Manufacturer Part Number: ISL6522A
• Description: Buck and Synchronous Rectifier Pulse-Width Modulator (PWM) Controller
• Manufacturer: Intersil Corporation

Typical Performance Curves
Functional Pin Descriptions
RT
This pin provides oscillator switching frequency adjustment.
By placing a resistor (R
200kHz switching frequency is increased according to the
following equation:
Conversely, connecting a pull-up resistor (R
V
following equation:
OCSET
Connect a resistor (R
upper MOSFET. R
(I
the converter overcurrent (OC) trip point according to the
following equation:
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
Fs
Fs 200kHz
I
OCS
PEAK
CC
≈
≈
1000
reduces the switching frequency according to the
200kHz
100
), and the upper MOSFET on-resistance (r
10
=
10
FIGURE 1. R
I
------------------------------------------- -
OCS
+
–
r
DS ON
4 10
------------------
5 10
------------------
•
•
•
R
R
R
(
OCSET
T
T
OCSET
7
6
SWITCHING FREQUENCY (kHz)
)
T
OCSET
RESISTANCE vs FREQUENCY
T
) from this pin to GND, the nominal
, an internal 200µA current source
(R
R
(R
T
T
T
) from this pin to the drain of the
PULLUP
TO +12V
R
to 12V)
to GND)
4
T
100
PULLDOWN
TO V
SS
T
) from this pin to
DS(ON)
) set
1000
ISL6522A
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
80
70
60
50
40
30
20
10
FIGURE 2. BIAS SUPPLY CURRENT vs FREQUENCY
0
100
200
300
SWITCHING FREQUENCY (kHz)
400
C
GATE
500
= 3300pF
600
C
GATE
C
GATE
700
= 1000pF
= 10pF
800
900
1000