ADP3209CJCPZ-RL ON Semiconductor, ADP3209CJCPZ-RL Datasheet - Page 27

• Manufacturer Part Number: ADP3209CJCPZ-RL
• Description: IC CTLR BUCK 5BIT 1PH 32LFCSP
• Manufacturer: ON Semiconductor

Specifications of ADP3209CJCPZ-RL

• Applications: Controller, Power Supplies for Next-Generation Intel Processors
• Voltage - Input: 3.3 ~ 22 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
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

RAMP RESISTOR SELECTION
The ramp resistor (R
ramp. The value of this resistor is chosen to provide the best
combination of stability and transient response. Use the
following expression to determine a starting value:
where:
Another consideration in the selection of R
internal ramp voltage (see Equation 20). For stability and noise
immunity, keep the ramp size larger than 0.5 V. Taking this into
consideration, the value of R
The internal ramp voltage magnitude can be calculated as follows:
The size of the internal ramp can be increased or decreased. If it
is increased, stability and transient response improves but
thermal balance degrades. Conversely, if the ramp size is
decreased, thermal balance improves but stability and transient
response degrade. In the denominator of Equation 19, the factor
of 3 sets the minimum ramp size that produces an optimal
balance of good stability and transient response.
COMP PIN RAMP
In addition to the internal ramp, there is a ramp signal on the
COMP pin due to the droop voltage and output voltage ramps.
This ramp amplitude adds to the internal ramp to produce the
following overall ramp signal at the PWM input:
where
resistance of the regulator.
For this example, the overall ramp signal is 0.23 V.
is the internal ramp amplifier gain.
is the internal ramp capacitor value.
is the current balancing amplifier gain.
is the total low-side MOSFET on resistance.
=
=
=
=
=
is the total bulk capacitance, and
3
3
0
340
§
¨
¨
©
×
2 .
×
1
5
×
×
−
0
×
kΩ
1 (
2 .
1 (
×
3
×
×
−
−
4 .
×
2
×
560
. 0
R
5
×
) is used to set the size of the internal PWM
mΩ
×
×
062
)
pF
(
1
×
×
nH
−
×
)
×
×
5
×
390
R
. 1
pF
)
in this example is selected as 340 kΩ.
174
kHz
=
·
¸
¸
¹
439
V
=
kΩ
. 0
33
V
R
is the size of the
is the droop
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(19)
(20)
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CURRENT LIMIT SETPOINT
To select the current limit setpoint, the resistor value for R
be determined. The current limit threshold for the ADP3209 is
set with R
where:
inductor switch node to the current sense amplifier.
If R
than expected and require an adjustment of R
example, I
supply. For this example, choosing 20 A for I
R
POWER MONITOR
The PMON duty cycle is proportional to the load current. R
sets the maximum duty cycle at the maximum current.
where
duty cycle, and
When PMON is connected with a pull-up resistor to the output
voltage, as shown in Figure 33, the average PMON voltage is
given by
FEEDBACK LOOP COMPENSATION DESIGN
Optimized compensation of the ADP3209 allows the best
possible response of the regulator’s output to a load change. The
basis for determining the optimum compensation is to make
the regulator and output decoupling appear as an output
impedance that is entirely resistive over the widest possible
frequency range, including dc, and that is equal to the droop
resistance (R
voltage droops in proportion with the load current at any load
current slew rate, ensuring the optimal position and allowing
the minimization of the output decoupling.
CLIM
is the current sense amplifier feedback resistor.
CLIM
is the resistor connecting the current sense resistor or
is the current limit setpoint.
of 104 kΩ.
is the sense current resistor or the inductor DCR.
is greater than 500 kΩ, the current limit may be lower
CLIM
CLIM
=
is the load current in amps when PMON is 100%
O
=
. R
). With the resistive output impedance, the output
=
is the average current limit for the output of the
(
(
CLIM
×
is the droop resistance in ohms.
10
can be found using the following equation:
×
×
×
10
×
×
10
10
μA
×
μA
μA
9 +
×
×
)
)
−
1
×
1
V
9
V
CLIM
CLIM
, results in an
. In this
CLIM
PMONFS
must
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