ISL6537ACRZ Intersil, ISL6537ACRZ Datasheet - Page 11

• Manufacturer Part Number: ISL6537ACRZ
• Description: IC REG/CTRLR ACPI DUAL DDR 28QFN
• Manufacturer: Intersil

Specifications of ISL6537ACRZ

• Applications: Memory, DDR/DDR2 Regulator
• Current - Supply: 7mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 28-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Supply: -

diagrams on page 4). An internal 20μA (typical) current sink
develops a voltage across R
converter input voltage. When the voltage across the upper
MOSFET (also referenced to the converter input voltage)
exceeds the voltage across R
initiates a soft-start sequence. The initiation of soft-start may
affect other regulators. The V
affected as it receives its reference and input from V
The overcurrent function will trip at a peak inductor current
(I
where I
typical). The OC trip point varies mainly due to the MOSFET
r
normal operating load range, find the R
the equation above with:
For an equation for the ripple current see the section under
component guidelines titled ‘Output Inductor Selection’.
A small ceramic capacitor should be placed in parallel with
R
presence of switching noise on the input voltage.
Thermal Protection (S0/S3 State)
If the ISL6537A IC junction temperature reaches a nominal
temperature of +140°C, all regulators will be disabled. The
ISL6537A will not re-enable the outputs until the junction
temperature drops below +110°C and either the bias voltage
is toggled in order to initiate a POR or the SLP_S5 signal is
forced LOW and then back to HIGH.
Shoot-Through Protection
A shoot-through condition occurs when both the upper and
lower MOSFETs are turned on simultaneously, effectively
shorting the input voltage to ground. To protect from a shoot-
through condition, the ISL6537A incorporates specialized
circuitry on the V
complementary MOSFETs are not ON simultaneously.
The adaptive shoot-through protection utilized by the V
regulator looks at the lower gate drive pin, LGATE, and the
upper gate drive pin, UGATE, to determine whether a
MOSFET is ON or OFF. If the voltage from UGATE or from
LGATE to GND is less than 0.8V, then the respective
MOSFET is defined as being OFF and the other MOSFET is
allowed to turned ON. This method allows the V
regulator to both source and sink current.
I
DS(ON)
1. The maximum r
2. The minimum I
3. Determine I
PEAK
PEAK)
OCSET
temperature.
where ΔI is the output inductor ripple current.
=
OCSET
determined by:
variations. To avoid overcurrent tripping in the
to smooth the voltage across R
I
---------------------------------------------------- -
OCSET
r
is the internal OCSET current source (20μA
DS ON
PEAK
DDQ
x R
(
OCSET
DS(ON)
OCSET
)
for
regulator which insures that
I
PEAK
from the specification table.
at the highest junction
OCSET
TT_DDR
OCSET
11
>
I
OUT MAX
that is referenced to the
, the overcurrent function
regulator is directly
(
OCSET
OCSET
)
+
(
--------- -
resistor from
ΔI
2
in the
DDQ
)
,
DDQ
(EQ. 3)
DDQ
.
ISL6537A
Since the voltage of the MOSFET gates are being measured
to determine the state of the MOSFET, the designer is
encouraged to consider the repercussions of introducing
external components between the gate drivers and their
respective MOSFET gates before actually implementing
such measures. Doing so may interfere with the shoot-
through protection.
Application Guidelines
Layout Considerations
Layout is very important in high frequency switching
converter design. With power devices switching efficiently at
250kHz, the resulting current transitions from one device to
another cause 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 board design minimizes these
voltage spikes.
As an example, consider the turn-off transition of the control
MOSFET. Prior to turn-off, the MOSFET is carrying the full
load current. During turn-off, current stops flowing in the
MOSFET and is picked up by the lower MOSFET. Any
parasitic 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 traces minimizes the magnitude of voltage
spikes.
There are two sets of critical components in the ISL6537A
switching converter. The switching components are the most
critical because they switch large amounts of energy, and
therefore tend to generate large amounts of noise. Next are
the small signal components which connect to sensitive
nodes or supply critical bypass current and signal coupling.
A multi-layer printed circuit board is recommended. Figure 2
shows the connections of the critical components in the
converter. Note that capacitors C
represent numerous physical capacitors. Dedicate one solid
layer, usually a middle layer of the PC 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 terminals to the output inductor short. The power
plane should support the 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 GATE pins to the MOSFET gates should be kept short
and wide enough to easily handle the 1A of drive current.
In order to dissipate heat generated by the internal V
LDO, the ground pad, pin 29, should be connected to the
internal ground plane through at least four vias. This allows
IN
and C
OUT
could each
TT
FN9143.5