ADP2380-EVALZ Analog Devices, ADP2380-EVALZ Datasheet - Page 20

• Manufacturer Part Number: ADP2380-EVALZ
• Description: Power Management IC Development Tools 20V 4A Evaluation Board
• Manufacturer: Analog Devices
• Type: DC/DC Converters, Regulators & Controllersr
• Series: ADP2380r

Specifications of ADP2380-EVALZ

• Rohs: yes
• Tool Is For Evaluation Of: ADP2380
• Input Voltage: 4.5 V to 20 V
• Factory Pack Quantity: 1

ADP2380
DESIGN EXAMPLE
This section provides the procedures for selecting the external
components based on the example specifications listed in Table 10.
The schematic of this design example is shown in Figure 36.
Table 10. Step-Down DC-to-DC Regulator Requirements
OUTPUT VOLTAGE SETTING
Choose a 10 kΩ resistor as the top feedback resistor (R
calculate the bottom feedback resistor (R
To set the output voltage to 3.3 V, the resistors values are
R
FREQUENCY SETTING
Connect a 100 kΩ resistor from the RT pin to GND to set the
switching frequency at 500 kHz.
INDUCTOR SELECTION
The peak-to-peak inductor ripple current, ∆I
the maximum output current. Use the following equation to
estimate the inductor value:
where:
V
V
D = V
∆I
f
This results in L = 3.987 μH. Choose the standard inductor
value of 4.7 μH.
Calculate the peak-to-peak inductor ripple current using the
following equation:
This results in ∆I
Calculate the peak inductor current using the following equation:
This results in I
SW
Parameter
Input Voltage
Output Voltage
Output Current
Output Voltage Ripple
Load Transient
Switching Frequency
TOP
IN
OUT
L
= 500 kHz.
= 12 V.
= 1.2A.
= 10 kΩ, R
= 3.3 V.
R
L
∆
I
OUT
PEAK
BOT
I
=
L
/V
(
=
V
=
=
IN
IN
(
V
∆
R
I
= 0.275.
−
I
IN
OUT
TOP
L
PEAK
BOT
V
L
L
×
−
OUT
×
= 1.02 A.
+
×
= 2.21 kΩ.
V
f
= 4.51 A.




SW
OUT
∆
)
V
f
2
I
SW
×
OUT
L
)
D
0
×
6 .
−
D
0
6 .




Specification
V
V
I
∆V
±5%, 1 A to 4 A, 2 A/μs
f
OUT
SW
IN
OUT
OUT_RIPPLE
= 12.0 V ± 10%
= 500 kHz
= 4 A
= 3.3 V
BOT
).
= 33 mV
L
, is set to 30% of
TOP
) and
Rev. 0 | Page 20 of 28
Calculate the rms current flowing through the inductor using
the following equation:
This results in I
According to the calculated rms and peak inductor current
values, select an inductor with a minimum rms current rating of
4.01 A and a minimum saturation current rating of 4.51 A.
To protect the inductor from reaching its saturation limit, the
inductor should be rated for at least a 7 A saturation current for
reliable operation.
Based on these requirements, select a 4.7 μH inductor, such as
the FDVE1040-4R7M from Toko, which has a 13.8 mΩ DCR
and an 8.2 A saturation current.
OUTPUT CAPACITOR SELECTION
The output capacitor is required to meet both the output voltage
ripple requirement and the load transient response.
To meet the output voltage ripple requirement, use the following
equation to calculate the ESR and capacitance of the output
capacitor:
This results in C
To meet the ±5% overshoot and undershoot transient
requirements, use the following equations to calculate the
capacitance:
where:
K
∆I
∆V
∆V
This results in C
According to the preceding calculation, the output capacitance
must be larger than 76 μF, and the ESR of the output capacitor
must be smaller than 32 mΩ. It is recommended that two pieces
of 47 μF/X5R/6.3 V ceramic capacitors be used, such as the
GRM32ER60J476ME20 from Murata, with an ESR of 2 mΩ.
OV
STEP
OUT_OV
OUT_UV
= K
C
C
C
I
R
= 3 A, the load transient step.
RMS
OUT
ESR
OUT
OUT
UV
= 5%V
= 5%V
=
= 2, the coefficients for estimation purposes.
_
=
_
_
OV
UV
RIPPLE
∆
I
V
OUT
=
=
RMS
OUT
OUT_RIPPLE
OUT
OUT
OUT_OV
(
2
∆
=
V
2
= 4.01 A.
I
×
_
, the overshoot voltage.
, the undershoot voltage.
OUT
+
8
L
RIPPLE
(
×
V
∆
K
= 76 μF and C
12
K
IN
I
f
+
UV
L
OV
SW
= 7.7 μF and R
2
∆
−
V
×
V
×
×
OUT
OUT
∆
∆
∆
∆
I
I
V
I
STEP
L
_
STEP
)
OUT
OV
×
2
∆
)
_
2
OUT_UV
2
RIPPLE
×
V
×
−
OUT
ESR
L
L
V
= 32 mΩ.
OUT
_
= 30 μF.
UV
Data Sheet
2