ISL6563IRZ Intersil, ISL6563IRZ Datasheet - Page 16
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ISL6563IRZ
Manufacturer Part Number
ISL6563IRZ
Description
IC CNTRLR PWM 2-PH BUCK 24-QFN
Manufacturer
Intersil
Datasheet
1.ISL6563IR.pdf
(19 pages)
Specifications of ISL6563IRZ
Applications
Controller, Intel VRM9, VRM10, and AMD Hammer Applications
Voltage - Input
5 ~ 12 V
Number Of Outputs
1
Voltage - Output
0.8 ~ 1.85 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
24-VQFN Exposed Pad, 24-HVQFN, 24-SQFN, 24-DHVQFN
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
ISL6563IRZ
Manufacturer:
Intersil
Quantity:
300
The output inductors must be capable of assuming the entire
load current before the output voltage decreases more than
ΔV
While the previous equation addresses the leading edge,
Equation 24 gives the upper limit on L for cases where the
trailing edge of the current transient causes a greater output
voltage deviation than the leading edge.
Normally, the trailing edge dictates the selection of L, since
duty cycles are usually less than 50%. Nevertheless, both
inequalities should be evaluated, and L should be selected
based on the lower of the two results. In all equations in this
paragraph, L is the per-channel inductance and C is the total
output bulk capacitance.
Layout Considerations
MOSFETs switch very fast and efficiently. The speed with
which the current transitions from one device to another
causes voltage spikes across the interconnecting
impedances and parasitic circuit elements. These voltage
spikes can degrade efficiency, radiate noise into the circuit
and lead to device overvoltage stress. Careful component
layout and printed circuit design minimizes the voltage
spikes in the converter. Consider, as an example, the turnoff
transition of the upper PWM MOSFET. Prior to turnoff, the
upper MOSFET was carrying channel current. During the
turnoff, current stops flowing in the upper MOSFET and is
picked up by the lower MOSFET. Any inductance in the
switched current path generates a large voltage spike during
the switching interval. Careful component selection, tight
layout of the critical components, and short, wide circuit
traces minimize the magnitude of voltage spikes.
There are two sets of critical components in a DC-DC
converter using an ISL6563 controller. The power
components are the most critical because they switch large
amounts of energy. Next are small signal components that
connect to sensitive nodes or supply critical bypassing
current and signal coupling.
Note that as the ISL6563 does not allow external adjustment
of the channel-to-channel current balancing (current
information is multiplexed across a single R
is important to have a symmetrical layout, preferably with the
controller equidistantly located from the two power trains it
controls. Equally important are the gate drive lines (UGATE,
LGATE, PHASE): since they drive the power train MOSFETs
using short, high current pulses, it is important to size them
accordingly and reduce their overall impedance. Equidistant
placement of the controller to the two power trains also helps
keeping these traces equally long (equal impedances,
resulting in similar driving of both sets of MOSFETs).
L
L
≤
≤
MAX
4 C V
--------------------------------
2.5 C
---------------- -
(
ΔI
⋅
(
⋅
)
. This places an upper limit on inductance.
ΔI
2
⋅
)
⋅
2
OUT
(
ΔV
MAX
⋅
(
ΔV
–
MAX
ΔI ESR
⋅
–
ΔI ESR
⋅
)
16
⋅
(
V
IN
)
–
V
O
)
ISEN
resistor), it
(EQ. 23)
(EQ. 24)
ISL6563
The power components should be placed first. Locate the
input capacitors close to the power switches. Minimize the
length of the connections between the input capacitors, C
and the power switches. Locate the output inductors and
output capacitors between the MOSFETs and the load.
Locate the high-frequency decoupling capacitors (ceramic)
as close as practicable to the decoupling target, making use
of the shortest connection paths to any internal planes, such
as vias to GND immediately next, or even onto the capacitor
solder pad.
The critical small components include the bypass capacitors
for VCC and PVCC. Locate the bypass capacitors, C
close to the device. It is especially important to locate the
components associated with the feedback circuit close to
their respective controller pins, since they belong to a high-
impedance circuit loop, sensitive to EMI pick-up. It is
important to place the R
terminal of the ISL6563.
A multi-layer printed circuit board is recommended. Figure 9
shows the connections of the critical components for one
output channel of the converter. Note that capacitors C
and C
capacitors. Dedicate one solid layer, usually the one
underneath the component side of the board, for a ground
plane and make all critical component ground connections
with vias to this layer. Dedicate another solid layer as a power
plane and break this plane into smaller islands of common
voltage levels. Keep the metal runs from the PHASE terminal
to inductor L
input power and output power nodes. Use copper filled
polygons on the top and bottom circuit layers for the phase
nodes. Use the remaining printed circuit layers for small signal
wiring. The wiring traces from the IC to the MOSFETs’ gates
and sources should be sized to carry at least one ampere of
current (0.02” to 0.05”).
Component Selection Guidelines
Output Capacitor Selection
The output capacitor is selected to meet both the dynamic
load requirements and the voltage ripple requirements. The
load transient a microprocessor impresses is characterized
by high slew rate (di/dt) current demands. In general,
multiple high quality capacitors of different size and dielectric
are paralleled to meet the design constraints.
Should the load be characterized by high slew rates, attention
should be particularly paid to the selection and placement of
high-frequency decoupling capacitors (MLCCs, typically
multi-layer ceramic capacitors). High frequency capacitors
supply the initially transient current and slow the load
rate-of-change seen by the bulk capacitors. The bulk filter
capacitor values are generally determined by the ESR
(effective series resistance) and capacitance requirements.
xxOUT
OUT
could each represent numerous physical
short. The power plane should support the
ISEN
resistor close to the respective
June 10, 2010
BP
xxIN
FN9126.8
,
IN
,