ADP3208C ON Semiconductor, ADP3208C Datasheet - Page 33

• Manufacturer Part Number: ADP3208C
• Description: 7-bit,programmable,dual- Phase,mobile,cpu,synchronous Buck Controller
• Manufacturer: ON Semiconductor

The following procedure and expressions yield values for
R
R
1.
2.
3.
4.
5.
CS1
CS
value.
, R
Select an NTC to be used based on its type and value.
Because the value needed is not yet determined, start with
a thermistor with a value close to R
initial tolerance of better than 5%.
Find the relative resistance value of the NTC at two
temperatures. The appropriate temperatures will depend
on the type of NTC, but 50°C and 90°C have been shown
to work well for most types of NTCs. The resistance values
are called A (A is R
R
NTC is always 1 at 25°C.
Find the relative value of R
temperatures. The relative value of R
percentage of change needed, which is initially assumed to
be 0.39%/°C in this example.
The relative values are called r
and r
T
Compute the relative values for r
the following equations:
Calculate R
the closest value available. In addition, compute a scaling
factor k based on the ratio of the actual thermistor value
used relative to the computed one:
r
r
r
CS2
CS1
TH
TH
1
CS2
is 50°C, and T
(90°C)/R
, and R
=
=
=
Figure 36. Temperature-Compensation Circuit Values
k =
2
(r
(
1
1
A
−
2
−
R
is 1/(1 + TC × (T
1
1
−
r
r
CS2
TH
A
CS2
R
TH
TH
B
1 (
TH
TH
1
×
(
)
(the thermistor value at 25°C) for a given
CALCULATED
= r
×
−
(25°C)). Note that the relative value of the
−
−
1 (
(
ACTUAL
r
r
A
r
2
−
TH
1
CS1
1
1
is 90°C.
)
×
B
−
TH
× R
A
r
)
r
2
(50°C)/R
×
CS2
)
−
CS
r
)
1
A
, and then select a thermistor of
−
2
CS
×
B
− 25))), where TC is 0.0039,
1 (
required for each of the two
×
1
TH
−
1 (
(r
(25°C)) and B (B is
CS1
B
1
−
)
is 1/(1+ TC × (T
, r
CS
×
A
CS
CS2
r
)
and an NTC with an
2
×
is based on the
, and r
+
r
2
B
−
×
(
1 (
A
TH
−
Rev. 1 | Page 33 of 41 | www.onsemi.com
−
by using
A
B
1
)
)
− 25)))
×
r
1
(8)
(7)
6.
For example, if a thermistor value of 100 kΩ is selected in Step 1,
an available 0603-size thermistor with a value close to R
Vishay NTHS0603N04 NTC thermistor, which has resistance
values of A = 0.3359 and B = 0.0771. Using the equations in
Step 4, r
yields 241 kΩ, so a thermistor of 220 kΩ would be a reasonable
selection, making k equal to 0.913. Finally, R
to be 72.1 kΩ and 166 kΩ. Choosing the closest 1% resistor for
R
is used for R
C
The required output decoupling for processors and platforms is
typically recommended by Intel. For systems containing both
bulk and ceramic capacitors, however, the following guidelines
can be a helpful supplement.
Select the number of ceramics and determine the total ceramic
capacitance (C
capacitors used. Keep in mind that the best location to place
ceramic capacitors is inside the socket; however, the physical
limit is twenty 0805-size pieces inside the socket. Additional
ceramic capacitors can be placed along the outer edge of the
socket. A combined ceramic capacitor value of 200 μF to 300 μF
is recommended and is usually composed of multiple 10 μF or
22 μF capacitors.
Ensure that the total amount of bulk capacitance (C
its limits. The upper limit is dependent on the VID on-the-fly
output voltage stepping (voltage step, V
of V
for load release at a given maximum load step, ΔI
version of the IMVP-6+ specification allows a maximum V
overshoot (V
step-off load current.
where
C
C
CS2
OUT
X
X
(
(
MAX
ERR
MIN
yields 165 kΩ. To correct for this approximation, 73.3 kΩ
Calculate values for R
equations:
Selection
); the lower limit is based on meeting the critical capacitance
)
k
)
≤
CS1
≥
=
n
R
R
⎛
⎜
⎜
⎜
⎜
⎜
⎝
−
is 0.359, r
×
CS1
CS2
n
CS1
ln
k
OSMAX
×
L
2
Z
.
=
=
⎛
⎜
⎜
⎝
×
). This is based on the number and type of
⎛
⎜
⎜
⎝
V
R
R
R
R
V
O
) of 10 mV more than the VID voltage for a
2
ERR
CS
CS
O
V
×
CS2
+
×
×
L
V
⎞
⎟
⎟
⎠
((
V
V
k
VID
×
is 0.729, and r
V
1
×
OSMAX
Δ
Δ
−
I
r
×
CS1
CS1
I
O
k
O
⎛
⎜
⎜
⎜
⎝
)
and R
+
⎞
⎟
⎟
⎠
1
(
×
+
k
⎛
⎜
⎜
⎝
V
×
t
CS2
r
VID
v
CS2
V
V
TH
VID
by using the following
V
))
−
V
is 1.094. Solving for r
, in time, t
C
×
CS1
ADP3208C
Z
n
⎞
⎟
⎟
⎟
⎟
⎟
⎠
×
and R
k
L
×
R
O
O
CS2
. The current
V
X
, with error
⎞
⎟
⎟
⎠
) is within
2
are found
−
CS
1
⎞
⎟
⎟
⎟
⎠
is the
−
CORE
(10)
(11)
C
(9)
TH
Z