ISL6530EVAL2

Manufacturer Part NumberISL6530EVAL2
DescriptionEVALUATION BOARD 2 ISL6530
ManufacturerIntersil
ISL6530EVAL2 datasheet
 


Specifications of ISL6530EVAL2

Main PurposeSpecial Purpose DC/DC, DDR Memory SupplyOutputs And Type2, Non-Isolated
Power - Output31.25WVoltage - Output2.5V, 1.25V
Current - Output10A, 5AVoltage - Input4.5 ~ 5.5V
Regulator TopologyBuckFrequency - Switching300kHz
Board TypeFully PopulatedUtilized Ic / PartISL6530
Lead Free Status / RoHS StatusContains lead / RoHS non-compliant  
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One method that may be employed to bypass the internal
V
reference generation is to supply an external reference
TT
directly to the V
pin. When doing this the SENSE1 pin
REF_IN
must remain unconnected. Caution must be exercised when
using this method as the V
regulator does not employ a
TT
soft-start of its own.
A second method would be to overdrive the internal
resistors. Figure 4 shows how to implement this method. The
external resistors used to overdrive the internal resistors
should be less than 2kΩ and have a tolerance of 1% or
better. This method still supplies a buffer between the
resistor network and any loading on the V
no loading on the V
pin, then no buffering is necessary
REF
and the reference voltage created by the resistor network
can be tied directly to V
.
REF
V
DDQ
SENSE1
VREF_IN
R
A
VREF
R
B
FIGURE 4. V
REFERENCE OVERDRIVE
TT
Converter Shutdown
Pulling and holding the OCSET/SD pin below 0.8V will
shutdown both regulators. During this state, PGOOD will be
held LOW. Upon release of the OCSET/SD pin, the IC enters
into a soft start cycle which brings both outputs back into
regulation.
Voltage Monitoring
The ISL6530 offers a PGOOD signal that will communicate
whether the regulation of both V
and V
DDQ
±15% of regulation, the V2_SD pin is held low and the bias
voltage of the IC is above the POR level. If all the criteria
above are true, the PGOOD pin will be at a high impedence
level. When one or more of the criteria listed above are false,
the PGOOD pin will be held low.
Overcurrent Protection
The overcurrent function protects the converter from a shorted
output by using the upper MOSFET on-resistance, r
V
to monitor the current. This method enhances the
DDQ
converter’s efficiency and reduces cost by eliminating a
current sensing resistor.
The over-current function cycles the soft-start function in a
hiccup mode to provide fault protection. A resistor (R
9
ISL6530
programs the overcurrent trip level (see Figure 1). An internal
40µA (typical) current sink develops a voltage across R
that is referenced to V
MOSFET of V
voltage across R
soft-start sequence.
Figure 5 illustrates the protection feature responding to an
over current event on V
condition is sensed across the upper MOSFET of the V
regulator. As a result, both regulators are quickly shutdown
and the internal soft-start function begins producing soft-
pin. If there is
start ramps. The delay interval seen by the output is
REF
equivalent to three soft-start cycles. The fourth internal soft-
start cycle initiates a normal soft-start ramp of the output, at
time T1. Both outputs are brought back into regulation by
time t2, as long as the overcurrent event has cleared.
ISL6530
Had the cause of the overcurrent still been present after the
delay interval, the overcurrent condition would be sensed
and both regulators would be shut down again for another
delay interval of three soft-start cycles. The resulting hiccup
mode style of protection would continue to repeat
indefinitely.
+
-
TO ERROR
AMPLIFIER
0V
are within
TT
FIGURE 5. OVERCURRENT PROTECTION RESPONSE
The overcurrent function will trip at a peak inductor current
(I
, of
PEAK)
DS(ON)
I
PEAK
where I
typical). The OC trip point varies mainly due to the MOSFET
)
OCSET
. When the voltage across the upper
IN
(also referenced to V
) exceeds the
DDQ
IN
, the overcurrent function initiates a
OCSET
. At time T0, an over current
DDQ
V
(2.5V)
DDQ
V
(1.25V)
TT
INTERNAL SOFT-START FUNCTION
DELAY INTERVAL
T0
T1
TIME
determined by:
I
x R
OCSET
OCSET
=
---------------------------------------------------- -
r
(
)
DS ON
is the internal OCSET current source (40µA
OCSET
OCSET
DDQ
T2
FN9052.2
November 15, 2004