ISL6545ACRZ Intersil, ISL6545ACRZ Datasheet - Page 10

• 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

sense resistor), the regular boot refresh circuit will still be
active.
Current Sinking
The ISL6545x incorporates a MOSFET shoot-through
protection method which allows a converter to sink current
as well as source current. Care should be exercised when
designing a converter with the ISL6545x when it is known
that the converter may sink current.
When the converter is sinking current, it is behaving as a
boost converter that is regulating its input voltage. This
means that the converter is boosting current into the V
rail, which supplies the bias voltage to the ISL6545x. If there
is nowhere for this current to go, such as to other distributed
loads on the V
device, or other methods, the capacitance on the V
will absorb the current. This situation will allow voltage level
of the V
boosted to a level that exceeds the maximum voltage rating
of the ISL6545x, then the IC will experience an irreversible
failure and the converter will no longer be operational.
Ensuring that there is a path for the current to follow other
than the capacitance on the rail will prevent this failure
mode.
Application Guidelines
Layout Considerations
As in any high frequency switching converter, layout is very
important. Switching current from one power device to another
can generate voltage transients across the impedances of the
interconnecting bond wires and circuit traces. These
interconnecting impedances should be minimized by using
wide, short printed circuit traces. The critical components
should be located as close together as possible, using ground
plane construction or single point grounding.
Figure 7 shows the critical power components of the converter.
To minimize the voltage overshoot, the interconnecting wires
indicated by heavy lines should be part of a ground or power
plane in a printed circuit board. The components shown should
be located as close together as possible. Please note that the
FIGURE 7. PRINTED CIRCUIT BOARD POWER AND
ISL6545,
ISL6545A
LGATE/OCSET
CC
UGATE
PHASE
rail to increase. If the voltage level of the rail is
GROUND PLANES OR ISLANDS
CC
rail, through a voltage limiting protection
Q
V
Q
RETURN
2
IN
1
10
C
IN
L
O
C
O
V
OUT
CC
ISL6545, ISL6545A
CC
bus
capacitors C
capacitors. For best results, locate the ISL6545x within 1 inch
of the MOSFETs, Q
MOSFET gate and source connections from the ISL6545x
must be sized to handle up to 1A peak current.
Figure 8 shows the circuit traces that require additional
layout consideration. Use single point and ground plane
construction for the circuits shown. Minimize any leakage
current paths on the COMP/SD pin and locate the resistor,
R
current source is only 20µA. Provide local V
between V
as close as practical to the BOOT and PHASE pins. All
components used for feedback compensation (not shown)
should be located as close to the IC as practical.
Feedback Compensation
This section highlights the design consideration for a
voltage-mode controller requiring external compensation. To
address a broad range of applications, a type-3 feedback
network is recommended, as shown in the top part of
Figure 9.
Figure 9 also highlights the voltage-mode control loop for a
synchronous-rectified buck converter, applicable to the
ISL6545x circuit. The output voltage (V
reference voltage, V
voltage) is compared with the oscillator (OSC) modified
sawtooth wave to provide a pulse-width modulated wave with
an amplitude of V
smoothed by the output filter (L and C). The output filter
capacitor bank’s equivalent series resistance is represented by
the series resistor E.
OSCET
FIGURE 8. PRINTED CIRCUIT BOARD SMALL SIGNAL
LGATE/OCSET
close to the COMP/SD pin because the internal
ISL6545A
ISL6545,
CC
IN
GND
LAYOUT GUIDELINES
and GND pins. Locate the capacitor, C
and C
IN
1
REF
at the PHASE node. The PWM wave is
O
and Q
BOOT
PHASE
VCC
C
may each represent numerous physical
. The error amplifier output (COMP pin
BOOT
2
+V
. The circuit traces for the
CC
C
VCC
OUT
Q
+V
Q
) is regulated to the
1
2
IN
CC
L
O
C
decoupling
O
March 3, 2011
BOOT
FN6305.6
V
OUT