ISL6526CR Intersil, ISL6526CR Datasheet - Page 13

• Manufacturer Part Number: ISL6526CR
• Description: IC CTRLR PWM SYNC BUCK 16-QFN
• Manufacturer: Intersil

Specifications of ISL6526CR

• Pwm Type: Voltage Mode
• Number Of Outputs: 1
• Frequency - Max: 325kHz
• Duty Cycle: 100%
• Voltage - Supply: 2.97 V ~ 3.63 V
• Buck: Yes
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 16-VQFN Exposed Pad, 16-HVQFN, 16-SQFN, 16-DHVQFN
• Frequency-max: 325kHz
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

where Q
MOSFET, C
the bootstrap voltage immediately before turn-on, and
V
The bootstrap capacitor begins its refresh cycle when the gate
drive begins to turn-off the upper MOSFET. A refresh cycle
ends when the upper MOSFET is turned on again, which
varies depending on the switching frequency and duty cycle.
The minimum bootstrap capacitance can be calculated by
rearranging the previous equation and solving for C
Typical gate charge values for MOSFETs considered in
these types of applications range from 20 to 100nC. Since
the voltage drop across Q
simply V
minimize the voltage drop across the bootstrap capacitor
during the on-time of the upper MOSFET. Initial calculations
with V
bootstrap capacitor range.
Component Selection Notes:
C
BOOT2
BOOT
C
D1 - 30mA Schottky Diode, MA732 or Equivalent
L
Q
1
3,
1
- 1µH Inductor, Panasonic P/N ETQ-P6F1ROSFA or Equivalent.
- Fairchild MOSFET; ITF86110DK8.
BOOT2
C
8,
GATE
CPVOUT
=
is the bootstrap voltage immediately after turn-on.
C
---------------------------------------------------- -
V
9
BOOT
BOOT1
- Each 150µF, Panasonic EEF-UE0J151R or Equivalent.
no less than 4V will quickly help narrow the
is the maximum total gate charge of the upper
3.3V
GND
Q
- V
ENABLE
GATE
is the bootstrap capacitance, V
–
D
V
. A Schottky diode is recommended to
BOOT2
0.22µF
LOWER
C
4
13
TP
is negligible, V
1
10
4
5
1
9
CT1
CT2
CPGND
GND
ENABLE
FIGURE 8. 3.3V TO 2.5V 5A DC/DC CONVERTER
COMP
8
ISL6526, ISL6526A
6.49kΩ
C
0.1µF
R
1
BOOT1
2
BOOT1
33pF
C
VCC
BOOT
ISL6526, ISL6526A
10
(EQ. 19)
5600pF
11
C
11
is
is
.
FB
CPVOUT
OCSET
UGATE
PHASE
LGATE
7
BOOT
1.07kΩ
U
R
1
5
13
14
12
6
3
2
For example, consider an upper MOSFET is chosen with a
maximum gate charge, Q
drop across the bootstrap capacitor to 1V results in a value
of no less than 0.1µF. The tolerance of the ceramic capacitor
should also be considered when selecting the final bootstrap
capacitance value.
A fast recovery diode is recommended when selecting a
bootstrap diode to reduce the impact of reverse recovery
charge loss. Otherwise, the recovery charge, Q
have to be added to the gate charge of the MOSFET and
taken into consideration when calculating the minimum
bootstrap capacitance.
ISL6526, ISL6526A DC/DC Converter
Application Circuit
Figure 8 shows an application circuit of a DC/DC Converter.
Detailed information on the circuit, including a complete Bill
of Materials and circuit board description, can be found in
Application Note AN1021:
http://www.intersil.com/data/an/an1021.pdf.
TP
D
C
124Ω
1
7
3
R
2.26kΩ
4
R
1000pF
3
0.1µF
9.76kΩ
8200pF
C
R
C
2
1
12
CERAMIC
10µF
CAP
C
5
Q
1
g
, of 100nC. Limiting the voltage
C
C
1µF
6
3
L
1
C
8, 9
2.5V @ 5A
GND
November 24, 2008
RR
, would
FN9055.10