ISL6545ACRZ Intersil, ISL6545ACRZ Datasheet - Page 14

• Manufacturer Part Number: ISL6545ACRZ
• Description: IC PWM BUCK BST VM 10DFN
• Manufacturer: Intersil

Specifications of ISL6545ACRZ

• Pwm Type: Voltage Mode
• Number Of Outputs: 1
• Frequency - Max: 660kHz
• Duty Cycle: 100%
• Voltage - Supply: 4.5 V ~ 14.4 V
• Buck: Yes
• Boost: Yes
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 10-DFN
• Frequency-max: 660kHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

BOOTSTRAP Considerations
Figure 11 shows the upper gate drive (BOOT pin) supplied by
a bootstrap circuit from V
develops a floating supply voltage referenced to the PHASE
pin. The supply is refreshed to a voltage of V
diode drop (V
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+
-
VCC
ISL6545x
+V
FIGURE 11. UPPER GATE DRIVE BOOTSTRAP
CC
+ V
GND
D
VCC
-
D
) each time the lower MOSFET, Q
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LGATE/OCSET
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BOOT
UGATE
PHASE
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CC
C
. The boot capacitor, C
14
BOOT
+V
IN
Q1
Q2
CC
V
V
G-S
G-S
less the boot
2
≈
≈
, turns on.
BOOT
V
V
CC
ISL6545, ISL6545A
CC
- V
,
D
Check that the voltage rating of the capacitor is above the
maximum V
sufficient for a 12V system. A value of 0.1µF is typical for
many systems driving single MOSFETs.
If V
option is to connect the BOOT pin to 12V, and remove the
BOOT cap (although, you may want to add a local cap from
BOOT to GND). This will make the UGATE V
equal to (12V - 5V = 7V). That should be high enough to
drive most MOSFETs, and low enough to improve the
efficiency slightly. Do NOT leave the BOOT pin open, and try
to get the same effect by driving BOOT through V
internal diode; this path is not designed for the high current
pulses that will result.
For low V
important, an external BOOT diode (in parallel with the
internal one) may be considered. The external diode drop
has to be lower than the internal one; the resulting higher
V
gain in efficiency should be balanced against the extra cost
and area of the external diode.
G-S
CC
of the upper FET will lower its r
is 12V, but V
CC
CC
voltage applications where efficiency is very
voltage in the system; a 16V rating should be
IN
is lower (such as 5V), then another
DS(ON)
. The modest
GS
voltage
CC
March 3, 2011
and the
FN6305.6