ADP3209JCPZ-RL ON Semiconductor, ADP3209JCPZ-RL Datasheet - Page 23

• Manufacturer Part Number: ADP3209JCPZ-RL
• Description: IC CTRLR BUCK 5BIT GMCH 32LFCSP
• Manufacturer: ON Semiconductor

Specifications of ADP3209JCPZ-RL

• Applications: Controller, Power Supplies for Next-Generation Intel Processors
• Voltage - Input: 4.5 ~ 5.5 V
• Number Of Outputs: 1
• Voltage - Output: 0.4 ~ 1.25 V
• Operating Temperature: 0°C ~ 100°C
• Mounting Type: Surface Mount
• Package / Case: 32-LFCSP
• Output Voltage: 0.4 V to 1.25 V
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 100 C
• Minimum Operating Temperature: 0 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: ADP3209JCPZ-RLTR

INDUCTOR SELECTION
The choice of inductance determines the ripple current of the
inductor. Less inductance results in more ripple current, which
increases the output ripple voltage and the conduction losses in
the MOSFETs. However, this allows the use of smaller-size
inductors, and for a specified peak-to-peak transient deviation,
it allows less total output capacitance. Conversely, a higher
inductance results in lower ripple current and reduced conduction
losses, but it requires larger-size inductors and more output
capacitance for the same peak-to-peak transient deviation. For
a buck converter, the practical value for peak-to-peak inductor
ripple current is less than 50% of the maximum dc current of
that inductor. Equation 5 shows the relationship between the
inductance, oscillator frequency, and peak-to-peak ripple
current. Equation 6 can be used to determine the minimum
inductance based on a given output ripple voltage.
In this example, R
capacitance, which results in an optimal transient response. Solving
Equation 6 for a 16 mV peak-to-peak output ripple voltage yields
If the resultant ripple voltage is less than the initially selected
value, the inductor can be changed to a smaller value until the
ripple value is met. This iteration allows optimal transient
response and minimum output decoupling. In this example, the
iteration showed that a 560 nH inductor was sufficient to
achieve a good ripple.
The smallest possible inductor should be used to minimize the
number of output capacitors. Choosing a 560 nH inductor is a
good choice for a starting point, and it provides a calculated
ripple current of 6.6 A. The inductor should not saturate at the
peak current of 18.3 A, and it should be able to handle the sum
of the power dissipation caused by the winding’s average current
(15 A) plus the ac core loss.
Another important factor in the inductor design is the DCR,
which is used for measuring the inductor current. Too large of a
DCR causes excessive power losses, whereas too small of a value
leads to increased measurement error. For this example, an
inductor with a DCR of 1.3 mΩ is used.
≥
≥
=
1.
174
×
V
3
×
0 9
1 (
×
×
O
5
−
×
kHz
×
is assumed to be the ESR of the output
1 .
1 (
mΩ
−
×
16
×
)
1 (
mV
)
−
. 0
062
)
=
901
nH
Rev. 2 | Page 23 of 32 | www.onsemi.com
(5)
(6)
After the inductance and DCR are known, select a standard
inductor that best meets the overall design goals. It is also
important to specify the inductance and DCR tolerance to
maintain the accuracy of the system. Using 20% tolerance for
the inductance and 15% for the DCR at room temperature are
reasonable values that most manufacturers can meet.
The following companies provide surface-mount power inductors
optimized for high power applications upon request.
•
•
•
•
The design requires that the regulator output voltage measured at
the chipset pins decreases when the output current increases. The
specified voltage drop corresponds to the droop resistance (R
The output current is measured by low-pass filtering the voltage
across the inductor or current sense resistor. The filter is
implemented by the CS amplifier that is configured with R
R
following equations:
where
Either R
current drive ability of the CSCOMP pin, the R
should be greater than 100 kΩ. For example, initially select R
to be equal to 200 kΩ, and then use Equation 8 to solve for C
If C
case, the required C
required. For best accuracy, C
Next, solve for R
CS
, and C
CS
Vishay Dale Electronics, Inc.
[phone]
Panasonic
[phone]
Sumida Electric Company
[phone]
NEC Tokin Corporation
[phone]
is not a standard capacitance, R
SENSE
CS
=
=
=
CS
or R
1
. The output resistance of the regulator is set by the
is the DCR of the output inductors.
3 .
PH
mΩ
×
560
PH
can be chosen for added flexibility. Due to the
×
by rearranging Equation 7 as follows:
×
CS
nH
200
is a standard value and no tuning is
kΩ
=
CS
2
should be a 5% NPO capacitor.
2 .
nF
CS
can be tuned. In this
CS
resistance
PH
,
CS
CS
O
(7)
(8)
).
: