ISL62881HRTZ-T Intersil, ISL62881HRTZ-T Datasheet - Page 19

• Manufacturer Part Number: ISL62881HRTZ-T
• Description: IC REG PWM SGL PHASE 28TQFN
• Manufacturer: Intersil

Specifications of ISL62881HRTZ-T

• Applications: Controller, Intel IMVP-6.5™
• Voltage - Input: 5 V ~ 25 V
• Number Of Outputs: 1
• Voltage - Output: 0.0125 V ~ 1.5 V
• Operating Temperature: -10°C ~ 100°C
• Mounting Type: *
• Package / Case: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 17 shows the output voltage ring back problem
during load transient response. The load current i
fast step change, but the inductor current i
accurately follow. Instead, i
system fashion due to the nature of current loop. The
ESR and ESL effect of the output capacitors makes the
output voltage V
However, the controller regulates V
droop current i
of i
causing the ring back problem. This phenomenon is not
observed when the output capacitors have very low ESR
and ESL, such as all ceramic capacitors.
Figure 18 shows two optional circuits for reduction of the
ring back. R
R
beginning of i
effect at steady state. Through proper selection of R
and C
V
100W. C
transient response waveforms on an actual board. The
recommended range for C
C
constant. It usually takes the parallel of two (or more)
capacitors to get the desired value. Figure 18 shows
FIGURE 18. OPTIONAL CIRCUITS FOR RING BACK
o
FIGURE 17. OUTPUT VOLTAGE RING BACK PROBLEM
i
n
, providing a lower impedance path than R
L
will not ring back. The recommended value for R
is the capacitor used to match the inductor time
; therefore it pulls V
ip
Rntcs
Rntc
values, i
ip
should be determined through tuning the load
ip
BACK
RING
REDUCTION
o
Rp
and C
droop
change. R
droop
o
i
O
dip quickly upon load current change.
OPTIONAL
ip
, which is a real-time representation
form an R-C branch in parallel with
can resemble i
i
L
Cn.1
o
Rn
ip
back to the level dictated by i
19
ip
L
and C
is 100pF~2000pF.
responds in first order
V
O
OPTIONAL
ip
Rip Cip
o
Cn.2
do not have any
o
+
according to the
-
Ri
rather than i
Vcn
ISUM+
ISL62881, ISL62881B
ISUM-
L
i
cannot
at the
o
L
has a
, and
ip
ip
is
L
,
that two capacitors C
Resistor R
ring back. At steady state, C
desired C
the effective capacitance is less because R
the impedance of the C
explains, V
effect will reduce the V
pronounced when C
also more pronounced when R
presence of R
C
greater than 2200pF. R
C
through tuning the load transient response waveforms
on an actual board.
R
providing a lower impedance path than R
beginning of i
effect at steady state. Through proper selection of R
and C
and V
R
the load transient response waveforms on an actual
board. The recommended range for C
100pF~2000pF. However, it should be noted that the
R
Instead of being triangular as the real inductor current,
i
affect i
may affect OCP accuracy. User discretion is advised.
Resistor Current-Sensing Network
Figure 19 shows the resistor current-sensing network.
The inductor has a series current-sensing resistor R
R
capture the inductor current information. The R
the sensed information to capacitor C
droop
FIGURE 19. RESISTOR CURRENT-SENSING NETWORK
sum
n.2
n.1
ip
ip
ip
and C
is 100Ω. C
-C
, C
is too small. It is recommended to keep C
o
and is connected to the R
ip
ip
may have sharp spikes, which may adversely
droop
n.2
will not ring back. The recommended value for
RSEN
values, i
branch may distort the i
DCR
n
ip
n
PHASE
Io
o
and R
L
capacitance. At the beginning of i
form an R-C branch in parallel with R
is an optional component to reduce the V
tends to dip when C
average value detection and therefore
n
o
ip
change. R
increases the ripple of the V
should be determined through tuning
droop
n
values should be determined
RSUM
n.1
n.1
can resemble i
o
n
n.1
is much larger than C
ring back. This effect is more
and C
value usually is a few ohms.
ip
Vcn
branch. As Figure 15
and C
n.1
n
sen
n.2
is bigger. However, the
+ C
n
droop
ip
Cn
is too small, and this
pad to accurately
are in parallel.
Ri
do not have any
n.2
n
o
. R
ip
waveform.
rather than i
provides the
is
sum
ISUM+
ISUM-
i
n
at the
n
increases
and C
o
n.2
sum
March 9, 2011
signal if
change,
n.2
. It is
FN6924.2
i
,
feeds
sen
n
L
,
ip
.
o