ADP2116-EVALZ AD [Analog Devices], ADP2116-EVALZ Datasheet - Page 26

• Manufacturer Part Number: ADP2116-EVALZ
• Description: Configurable, Dual 3 A/Single 6 A, Synchronous, Step-Down DC-to-DC Regulator
• Manufacturer: AD [Analog Devices]

ADP2116
EXTERNAL COMPONENTS SELECTION
INPUT CAPACITOR SELECTION
The input current to a buck converter is pulsating in nature. The
current is zero when the high-side switch is off and approximately
equal to the load current when the high-side switch is on. Because
this pulsation occurs at reasonably high frequencies (300 kHz to
1.2 MHz), the input bypass capacitor supplies most of the high
frequency current (ripple current), allowing the input power source
to supply only the average (dc) current. The input capacitor needs a
sufficient ripple current rating to handle the input ripple, as well
as an ESR that is low enough to mitigate the input voltage ripple.
For the ADP2116, place a 22 μF, 6.3 V X5R ceramic capacitor
close to the VINx pin for each channel. X5R or X7R dielectrics
are recommended with a voltage rating of 6.3 V or 10 V. Y5V
and Z5U dielectrics are not recommended due to their poor
temperature and dc bias characteristics.
VDD RC FILTER
It is recommended that the input power, V
VDD pin through a low-pass RC filter, as shown in Figure 68.
Connecting a 10 Ω resistor in series with V
(or X7R) ceramic capacitor between VDD and GND creates a
16 kHz (−3 dB) low-pass filter that effectively attenuates voltage
glitches on the input power rail caused by the switching regulator.
This provides a clean power supply to the internal, sensitive analog
and digital circuits in the ADP2116, ensuring robust operation.
INDUCTOR SELECTION
The high switching frequency of the ADP2116 allows for minimal
output voltage ripple even with small inductors. The size of the
inductor is a trade-off between efficiency and transient response. A
small inductor leads to larger inductor current ripple that provides
excellent transient response but degrades efficiency. Due to the
high switching frequency of the ADP2116, shielded ferrite core
inductors are recommended for their low core losses and low EMI.
V
Figure 68. Low-Pass Filter at VDD
IN
10Ω
1µF
VDD
GND
ADP2116
IN
IN
and a 1 μF, 6.3 V X5R
, be apply to the
Rev. 0 | Page 26 of 36
As a guideline, the inductor peak-to-peak current ripple, ΔI
typically set to be one-third of the maximum load current for
optimal transient response and efficiency.
where:
V
V
f
The internal slope compensation introduces additional limitations
on the optimal inductor value for stable operation because the
internal ramp is scaled for each V
different V
Table 8. Minimum and Maximum Inductor Values
f
300
300
300
300
300
300
300
300
300
300
300
600
600
600
600
600
600
600
600
600
600
600
1200
1200
1200
1200
1200
1200
1200
1200
1200
SW
SW
IN
OUT
is the converter switching frequency.
(kHz)
is the input voltage on the VINx terminal.
⇒
is the desired output voltage.
Δ
I
L
L
=
IDEAL
IN
V
, V
V
5
5
3.3
5
3.3
5
3.3
5
3.3
5
3.3
5
5
3.3
5
3.3
5
3.3
5
3.3
5
3.3
5
5
3.3
5
3.3
5
3.3
5
3.3
OUT
IN
V
=
OUT
(V)
IN
3
×
f
, and f
×
SW
(
×
V
V
IN
f
OUT
×
SW
V
−
SW
IN
V
3.3
2.5
2.5
1.8
1.8
1.5
1.5
1.2
1.2
0.8
0.8
3.3
2.5
2.5
1.8
1.8
1.5
1.5
1.2
1.2
0.8
0.8
2.5
1.8
1.8
1.5
1.5
1.2
1.2
0.8
0.8
×
V
×
OUT
L
OUT
(
combinations are listed in Table 8.
×
V
I
IN
(V)
LOAD
)
−
≈
OUT
V
(
I
MAX
OUT
LOAD
Min L (μH)
6.8
5.6
5.6
4.7
4.7
2.2
2.2
2.2
2.2
1.5
1.5
3.3
3.3
3.3
2.2
2.2
1.5
1.5
1.5
1.5
1.0
1.0
1.0
1.0
1.0
0.8
0.8
0.8
0.8
0.47
0.47
setting. The limits for
)
)
3
(MAX
)
Max L (μH)
10
15
6.8
12
8.2
12
8.2
10
8.2
6.8
6.8
4.7
6.8
3.3
6.8
3.3
5.6
4.7
4.7
3.3
3.3
3.3
3.3
3.3
2.2
2.2
2.2
2.2
2.2
1.5
1.5
L
, is
(5)