ADP2380-EVALZ Analog Devices, ADP2380-EVALZ Datasheet - Page 17

• 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

Data Sheet
OUTPUT CAPACITOR SELECTION
The output capacitor selection affects both the output ripple
voltage and the loop dynamics of the regulator.
During a load step transient on the output, for example, when
the load is suddenly increased, the output capacitor supplies the
load until the control loop has a chance to ramp up the inductor
current, which causes the output to undershoot. The output
capacitance required to satisfy the voltage droop requirement
can be calculated using the following equation:
where:
K
ΔI
ΔV
Another case occurs when a load is suddenly removed from
the output. The energy stored in the inductor rushes into the
capacitor, which causes the output to overshoot. The output
capacitance required to meet the overshoot requirement can
be calculated using the following equation:
where:
K
ΔV
The output ripple is determined by the ESR and the capaci-
tance. Use the following equation to select a capacitor that can
meet the output ripple requirements:
where:
ΔV
R
Table 8. Recommended MOSFETs
Vendor
Fairchild
Fairchild
Fairchild
Vishay
AOS
AOS
ESR
UV
OV
STEP
OUT_UV
OUT_OV
OUT_RIPPLE
is a factor, typically, of 2.
is a factor typically of 2.
is the equivalent series resistance of the output capacitor.
C
C
C
R
is the load step.
OUT
OUT
ESR
OUT
is the allowable overshoot on the output voltage.
is the allowable undershoot on the output voltage.
_
_
=
_
UV
RIPPLE
OV
is the allowable output ripple voltage.
∆
V
=
=
OUT
2
∆
(
V
=
×
I
_
OUT
L
8
RIPPLE
(
V
×
K
IN
K
UV
+
f
OV
−
SW
∆
V
Part No.
FDS6298
FDS8880
FDMS7578
SiA430DJ
AON7402
AO4884L
×
V
×
OUT
×
∆
OUT
∆
I
∆
∆
STEP
I
I
)
V
STEP
_
L
×
OUT
OV
∆
2
V
2
)
×
_
2
OUT
×
RIPPLE
L
−
L
V
_
OUT
UV
2
V
30
30
25
20
30
40
DS
(V)
Rev. 0 | Page 17 of 28
Select the largest output capacitance given by C
and C
performance.
The selected output capacitor voltage rating should be greater
than the output voltage. The rms current rating of the output
capacitor should be larger than the result of the following equation:
LOW-SIDE POWER DEVICE SELECTION
The
drives the low-side NFET. The selection of the low-side NFET
affects the dc-to-dc regulator performance.
The selected MOSFET must meet the following requirements:
•
•
•
•
•
Some recommended MOSFETs are listed in Table 8.
I
13
10.7
17
10.8
39
10
D
(A)
ADP2380
Drain-source voltage (VDS) must be greater than
1.2 × VIN.
Drain current (ID) must be greater than 1.2 × I
which is the selected maximum current-limit threshold.
The
that the selected MOSFET can fully turn on at 8 V. Total
gate charge (Qg at 8 V) must be less than 50 nC. Lower Qg
characteristics constitute higher efficiency.
The low-side MOSFET carries the inductor current when
the high-side MOSFET is turned off. For low duty cycle
applications, the low-side MOSFET carries the output
current during most of the period. To achieve higher
efficiency, it is important to select a low on-resistance
MOSFET. The power conduction loss of the low-side
MOSFET can be calculated by using the following
equation:
where R
Make sure that the MOSFET can handle the thermal
dissipation due to the power loss.
I
OUT_RIPPLE
C
OUT
ADP2380
P
_
FET_LOW
RMS
DSON
has an integrated low-side MOSFET driver that
to meet both load transient and output ripple
=
is the on resistance of the low-side MOSFET.
∆
= I
12
I
low-side gate drive voltage is 8 V. Ensure
L
R
12
12
8
18.5
15
16
OUT
DSON
2
× R
(mΩ)
DSON
× (1 – D)
Q
10
12
8
5.3
7.1
13.6
g
(nC)
OUT_UV
ADP2380
LIMIT_MAX
, C
OUT_OV
,
,