ISL6522EVAL1 Intersil, ISL6522EVAL1 Datasheet - Page 8

• Manufacturer Part Number: ISL6522EVAL1
• Description: EVALUATION BOARD ISL6522
• Manufacturer: Intersil

Specifications of ISL6522EVAL1

• Main Purpose: DC/DC, Step Down
• Voltage - Input: 10.8 ~ 13.2V
• Regulator Topology: Buck
• Board Type: Fully Populated
• Utilized Ic / Part: ISL6522
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Current - Output: -
• Voltage - Output: -
• Power - Output: -
• Frequency - Switching: -
• Outputs And Type: -

maximum voltage rating of the ISL6522 may be exceeded and
the IC will experience a catastrophic 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 these failure modes.
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 5 shows the critical power components of the
converter. To minimize the voltage overshoot the
interconnecting wires indicated by heavy lines should be part
of ground or power plane in a printed circuit board. The
components shown in Figure 6 should be located as close
together as possible. Please note that the capacitors C
and C
Locate the ISL6522 within three inches of the MOSFETs, Q1
and Q2. The circuit traces for the MOSFETs’ gate and
source connections from the ISL6522 must be sized to
handle up to 1A peak current.
Figure 6 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 SS PIN and locate the capacitor, C
close to the SS pin because the internal current source is
only 10µA. Provide local V
GND pins. Locate the capacitor, C
to the BOOT and PHASE pins.
FIGURE 5. PRINTED CIRCUIT BOARD POWER AND
ISL6522
O
each represent numerous physical capacitors.
UGATE
PHASE
LGATE
PGND
GROUND PLANES OR ISLANDS
CC
V
Q2
Q1
RETURN
IN
decoupling between VCC and
8
D2
BOOT
C
as close as practical
IN
L
O
C
O
V
OUT
IN
SS
ISL6522
Feedback Compensation
Figure 7 highlights the voltage-mode control loop for a
synchronous rectified buck converter. The output voltage
(V
amplifier (error amp) output (V
oscillator (OSC) triangular wave to provide a pulse-width
modulated (PWM) wave with an amplitude of V
PHASE node. The PWM wave is smoothed by the output filter
(L
The modulator transfer function is the small-signal transfer
function of V
gain and the output filter (L
break frequency at F
the modulator is simply the input voltage (V
peak-to-peak oscillator voltage ∆V
O
OUT
C
FIGURE 6. PRINTED CIRCUIT BOARD SMALL SIGNAL
SS
SS
and C
) is regulated to the reference voltage level. The error
ISL6522
O
GND
).
OUT
LAYOUT GUIDELINES
/V
E/A
LC
PHASE
C
VCC
BOOT
. This function is dominated by a DC
BOOT
and a zero at F
+12V
O
and C
C
E/A
VCC
D1
) is compared with the
OSC
O
), with a double pole
.
ESR
Q1
+V
Q2
IN
IN
. The DC gain of
L
) divided by the
O
IN
C
O
at the
March 10, 2006
FN9030.8
V
OUT