ISL6525 Intersil Corporation, ISL6525 Datasheet - Page 4

• Manufacturer Part Number: ISL6525
• Description: Buck and Synchronous-Rectifier Pulse-Width Modulator (PWM) Controller
• Manufacturer: Intersil Corporation

Typical Performance Curves
Functional Pin Descriptions
RT (Pin 1)
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
to V
following equation.:
OCSET (Pin 2)
Connect a resistor (R
upper MOSFET. R
(I
the converter over-current (OC) trip point according to the
following equation:
I
An over-current trip cycles the soft-start function.
SS (Pin 3)
Connect a capacitor from this pin to ground. This capacitor,
along with an internal 10 A current source, sets the soft-
start interval of the converter.
COMP (Pin 4) and FB (Pin 5)
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.
Fs 200kHz
Fs 200kHz
PEAK
OCS
CC
1000
100
), and the upper MOSFET on-resistance (r
10
=
reduces the switching frequency according to the
10
FIGURE 1. R
I
------------------------------------------- -
OCS
r
+
–
DS ON
-------------------- -
R
-------------------- -
R
5 10
4 10
T
R
T
OCSET
k
k
OCSET
7
SWITCHING FREQUENCY (kHz)
6
T
OCSET
RESISTANCE vs FREQUENCY
T
R
) from this pin to GND, the nominal
, an internal 200 A current source
T
TO +12V
(R
(R
PULLUP
T
R
T
) from this pin to the drain of the
T
to 12V)
to GND)
4
PULLDOWN
TO V
100
SS
T
) from this pin
DS(ON)
1000
) set
ISL6525
GND (Pin 6)
Signal ground for the IC. All voltage levels are measured with
respect to this pin.
PGOOD (Pin 7)
PGOOD is an open-drain output used to indicate the status
of the converter output voltage. This pin is pulled low when
the converter output is not within 10% of the set voltage. A
delay time can be programmed using the DELAY pin (pin
14). See Pin 14 description for more information.
PHASE (Pin 8)
Connect the PHASE pin to the upper MOSFET source. This
pin is used to monitor the voltage drop across the MOSFET
for over-current protection. This pin also provides the return
path for the upper gate drive.
UGATE (Pin 9)
Connect UGATE to the upper MOSFET gate. This pin
provides the gate drive for the upper MOSFET.
BOOT (Pin 10)
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 (Pin 11)
This is the power ground connection. Tie the lower MOSFET
source to this pin.
LGATE (Pin 12)
Connect LGATE to the lower MOSFET gate. This pin
provides the gate drive for the lower MOSFET.
VCC (Pin 13)
Provide a 12V bias supply for the chip to this pin.
DELAY (Pin 14)
This pin is used to program the delay of the PGOOD (pin 7)
signal by placing a capacitor between this pin and GND or
VCC. The external capacitor only delays the rising edge of
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