ISL6527AEVAL2 Intersil, ISL6527AEVAL2 Datasheet - Page 8

• Manufacturer Part Number: ISL6527AEVAL2
• Description: EVALUATION BOARD QFN ISL6527A
• Manufacturer: Intersil

Specifications of ISL6527AEVAL2

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 0.75 ~ 3V
• Current - Output: 5A
• Voltage - Input: 3.3 ~ 5V
• Regulator Topology: Buck
• Frequency - Switching: 600kHz
• Board Type: Fully Populated
• Utilized Ic / Part: ISL6527A
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

Output Voltage Selection
The output voltage can be programmed to any level between
V
divider is used to scale the output voltage relative to the
reference voltage and feed it back to the inverting input of the
error amplifier, see Figure 2. However, since the value of R
affects the values of the rest of the compensation
components, it is advisable to keep its value less than 5kΩ. R
can be calculated based on Equation 3:
If the output voltage desired is V
back to the FB pin through R
Overcurrent Protection
The overcurrent function protects the converter from a shorted
output by using the upper MOSFET ON-resistance, r
to monitor the current. This method enhances the converter’s
efficiency and reduces cost by eliminating a current sensing
resistor.
The overcurrent function cycles the soft-start function in a
hiccup mode to provide fault protection. A resistor (R
programs the overcurrent trip level (see Typical Application
diagrams on page 3 and page 4). An internal 20µA (typical)
current sink develops a voltage across R
referenced to V
MOSFET (also referenced to V
R
sequence.
Figure 3 illustrates the protection feature responding to an
overcurrent event. At time t0, an overcurrent condition is
sensed across the upper MOSFET. As a result, the regulator
R
IN
OCSET
4
and the supplied external reference. An external resistor
=
----------------------------------------
V
OUT1
R
, the overcurrent function initiates a soft-start
ISL6527A
ISL6527,
+3.3V
FIGURE 2. OUTPUT VOLTAGE SELECTION
1
×
VCC
V
–
REF
V
IN
REF
. When the voltage across the upper
CPVOUT
BOOT
UGATE
PHASE
LGATE
FB
COMP
REF_IN
C2
1
C4
D1
, but do not populate R
C1
8
IN
VIN
R2
REF
Q2
) exceeds the voltage across
VREF
Q1
, simply route the output
LOUT
COUT
R4
R1
C3
OCSET
+
R3
that is
VOUT
OCSET
ISL6527, ISL6527A
DS(ON)
4
.
(EQ. 3)
1
)
4
,
is quickly shutdown and the internal soft-start function begins
producing soft-start ramps. The delay interval seen by the
output is equivalent to three soft-start cycles. The fourth
internal soft-start cycle initiates a normal soft-start ramp of the
output, at time t1. The output is brought back into regulation
by time t2, as long as the overcurrent event has cleared.
Had the cause of the overcurrent still been present after the
delay interval, the overcurrent condition would be sensed
and the regulator 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.
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
operating load range, find the R
Equation 4 with:
I
DS(ON)
1. The maximum r
2. The minimum I
3. Determine I
PEAK)
PEAK
0V
temperature.
page 7.
where ΔI is the output inductor ripple current.
FIGURE 3. OVERCURRENT PROTECTION RESPONSE
OCSET
=
determined by Equation 4:
variations. To avoid overcurrent tripping in the normal
t0
I
---------------------------------------------------- -
OCSET
VOUT (2.5V)
INTERNAL SOFT-START FUNCTION
r
is the internal OCSET current source (20µA
DS ON
PEAK
x R
(
DELAY INTERVAL
OCSET
DS(ON)
OCSET
for
)
I
PEAK
from the “Specification Table” on
at the highest junction
TIME
OCSET
>
I
OUT MAX
(
resistor from the
t1
)
+
(
--------- -
ΔI
November 18, 2008
2
)
,
t2
FN9056.10
(EQ. 4)