ISL62882HRTZ-T Intersil, ISL62882HRTZ-T Datasheet - Page 21

• Manufacturer Part Number: ISL62882HRTZ-T
• Description: IC REG PWM 2PHASE BUCK 40TQFN
• Manufacturer: Intersil

Specifications of ISL62882HRTZ-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

Key Component Selection
R
The ISL62882 uses a resistor (1% or better tolerance is
recommended) from the RBIAS pin to GND to establish
highly accurate reference current sources inside the IC.
Refer to Table 2 to select the resistance according to
desired configuration. Do not connect any other
components to this pin. Do not connect any capacitor to
the RBIAS pin as it will create instability.
Care should be taken in layout that the resistor is placed
very close to the RBIAS pin and that a good quality signal
ground is connected to the opposite side of the R
resistor.
R
As Figures 1 thru 4 show, the ISL62882 needs the R
- C
stabilize the droop amplifier. The preferred values are
R
recommended values are acceptable. Large deviations
may result in instability.
Inductor DCR Current-Sensing Network
Figure 17 shows the inductor DCR current-sensing
network for a 2-phase solution. An inductor current flows
through the DCR and creates a voltage drop. Each
inductor has two resistors in R
the pads to accurately sense the inductor current by
sensing the DCR voltage drop. The R
are connected in a summing network as shown, and feed
the total current information to the NTC network
(consisting of R
is a negative temperature coefficient (NTC) thermistor,
used to temperature-compensate the inductor DCR
change.
The inductor output side pads are electrically shorted in
the schematic, but have some parasitic impedance in
is
BIAS
is
DCR
is
= 82.5Ω and C
FIGURE 17. DCR CURRENT-SENSING NETWORK
and C
Phase1
L
network across the ISUM+ and the ISUM- pins to
Io
DCR
is
Phase2
L
ntcs
is
, R
= 0.01µF. Slight deviations from the
Rsum
Rsum
ntc
Ro
Ro
Rntcs
Rntc
and R
21
sum
p
Rp
) and capacitor C
and R
sum
o
and R
ISL62882, ISL62882B
connected to
Cn
Ri
Vcn
o
resistors
ISUM+
BIAS
ISUM-
n
. R
is
ntc
actual board layout, which is why one cannot simply
short them together for the current-sensing summing
network. It is recommended to use 1Ω~10Ω R
quality signals. Since R
rest of the current sensing circuit, the following analysis
will ignore it for simplicity.
The summed inductor current information is presented to
the capacitor C
frequency-domain relationship between inductor total
current I
R
where N is the number of phases.
Transfer function A
inductor DCR value increases as the winding temperature
increases, giving higher reading of the inductor DC
current. The NTC R
temperature decreases. Proper selections of R
R
inductor total DC current over the temperature range of
interest.
There are many sets of parameters that can properly
temperature-compensate the DCR change. Since the
NTC network and the R
divider, V
voltage. It is recommended to have a higher ratio of V
to the inductor DCR voltage, so the droop circuit has
higher signal level to work with.
A typical set of parameters that provide good
temperature compensation are: R
11kΩ, R
The NTC network parameters may need to be fine tuned
on actual boards. One can apply full load DC current
and record the output voltage reading immediately;
then record the output voltage reading again when the
board has reached the thermal steady state. A good
NTC network can limit the output voltage drift to within
2mV. It is recommended to follow the Intersil evaluation
V
A
ω
ω
p
Cn
ntcnet
cs
L
sns
and R
s ( )
=
s ( )
=
DCR
-------------
=
L
=
--------------------------------------------------------
=
R
------------------------------------------
R
ntcs
o
---------------------- -
1
ntcnet
ntcnet
ntc
⎛
⎜
⎜
⎜
⎝
cn
(
----------------------------------------------------
1
(s) and C
------------------------------------------
R
R
R
+
+
ntcnet
ntcs
ntcs
------------ -
ω
is always a fraction of the inductor DCR
= 2.61kΩ and R
parameters ensure that V
------ -
ω
sns
R
s
s
L
×
+
ntcnet
n
+
+
1
R
-------------- -
R
-------------- -
. Equations 14 thru 18 describe the
+
R
R
sum
sum
N
N
ntc
ntc
R
-------------- -
cs
n
ntc
sum
N
(s) always has unity gain at DC. The
)
×
voltage V
+
×
C
R
values decreases as its
o
R
sum
×
p
n
p
value is much smaller than the
DCR
-------------
N
resistors form a voltage
ntc
⎞
⎟
⎟
⎟
⎠
Cn
×
= 10kΩ (ERT-J1VR103J).
I
(s).
o
s ( )
sum
×
A
Cn
= 3.65kΩ, R
cs
represent the
s ( )
sum
o
to create
, R
FN6890.3
(EQ. 14)
(EQ. 15)
(EQ. 16)
(EQ. 17)
(EQ. 18)
p
ntcs
=
cn
,