ISL6540A Intersil Corporation, ISL6540A Datasheet - Page 15

• Manufacturer Part Number: ISL6540A
• Description: Single-Phase Buck PWM Controller
• Manufacturer: Intersil Corporation

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/undershoot the
interconnecting wires indicated by heavy lines should be part
of ground or power plane in a printed circuit board. The
ISL6540A
FIGURE 7. PRINTED CIRCUIT BOARD POWER AND
UGATE
PHASE
LGATE
PGND
GROUND PLANES OR ISLANDS
VOUT (LOCAL)
GND (LOCAL)
FIGURE 6. SIMPLIFIED UNITY GAIN DIFFERENITAL SENSING IMPLEMENTATION
V
Q2
Q1
RETURN
IN
15
1.8V
VCC
C
10Ω
10Ω
IN
L
(REMOTE)
VSENSE-
O
C
O
VSEN-
V
OUT
R
C
OS
SEN
(REMOTE)
VSENSE+
ISL6540A
VSEN+
R
GAIN=1
FB
V
SS
components shown in Figure 8 should be located as close
together as possible. Please note that the capacitors C
and C
Locate the ISL6540A within 3 inches of the MOSFETs, Q1
and Q2. The circuit traces for the MOSFETs’ gate and
source connections from the ISL6540A must be sized to
handle up to 4A peak current.
Proper grounding of the IC is important for correct operation
in noisy environments. The PGND pin should be connected
to board ground at the source of the low side MOSFET with
a wide short trace. The GND pin should be connected to a
large copper fill under the IC which is subsequently
connected to board ground at a quite location on the board,
typically found at an input or output bulk (electrolytic)
capacitor.
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
VMON
C
FIGURE 8. PRINTED CIRCUIT BOARD SMALL SIGNAL
SS
SS
Z
OV/UV
COMP
O
IN
each represent numerous physical capacitors.
ISL6540A
GND
LAYOUT GUIDELINES
ERROR AMP
FB
PGND
Z
FB
PHASE
C
PVCC
BOOT
BOOT
+5V
COMP
C
PVCC
D1
Q1
+V
Q2
IN
L
O
C
O
March 12, 2007
FN6288.2
V
IN
OUT