ADP2106 Analog Devices, ADP2106 Datasheet - Page 17

• Manufacturer Part Number: ADP2106
• Description: 1.5 Amp Synchronous, Step-Down DC-to-DC Converter
• Manufacturer: Analog Devices

When R
(R
The ADP2105/ADP2106/ADP2107(x.x V) include the resistive
voltage divider internally, reducing the external circuitry required.
For improved load regulation, connect the FB to the output
voltage as close as possible to the load.
INDUCTOR SELECTION
The high switching frequency of ADP2105/ADP2106/ADP2107
allows for minimal output voltage ripple even with small inductors.
The sizing 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
ADP2105/ADP2106/ADP2107, shielded ferrite core inductors
are recommended for their low core losses and low electromagnetic
interference (EMI).
As a guideline, the inductor peak-to-peak current ripple (ΔI
typically set to 1/3 of the maximum load current for optimal
transient response and efficiency, as shown in the following
equations:
where f
The ADP2105/ADP2106/ADP2107 use slope compensation in
the current control loop to prevent subharmonic oscillations
when operating beyond 50% duty cycle. The fixed slope compen-
sation limits the minimum inductor value as a function of
output voltage.
For the ADP2105
For the ADP2106
For the ADP2107
Inductors 4.7 μH or larger are not recommended because they
may cause instability in discontinuous conduction mode under
light load conditions. It is also important that the inductor be
capable of handling the maximum peak inductor current (I
determined by the following equation:
TOP
) by using the following equation:
L > (1.12 μH/V) × V
L > (0.83 μH/V) × V
L > (0.66 μH/V) × V
R
Δ
⇒
I
PK
TOP
I
SW
L
BOT
L
=
=
IDEAL
is the switching frequency (1.2 MHz).
=
I
is determined, calculate the value of the top resistor
V
LOAD
R
OUT
BOT
V
=
(
IN
MAX
×
2
⎡
⎢
⎣
V
5 .
(
×
V
OUT
)
×
IN
f
V
+
V
SW
V
IN
FB
⎛ Δ
⎜
⎝
−
OUT
−
V
×
×
OUT
OUT
OUT
V
2
I
FB
L
I
OUT
×
L
LOAD
⎞
⎟
⎠
⎤
⎥
⎦
(
V
)
IN
( MAX
≈
−
I
V
LOAD
)
OUT
3
(MAX
)
μ
H
)
PK
L
Rev. C | Page 17 of 36
) is
)
Ensure that the maximum rms current of the inductor is greater
than the maximum load current and that the saturation current
of the inductor is greater than the peak current limit of the
converter used in the application.
Table 6. Minimum Inductor Value for Common Output
Voltage Options for the ADP2105 (1 A)
V
1.2 V
1.5 V
1.8 V
2.5 V
3.3 V
Table 7. Minimum Inductor Value for Common Output
Voltage Options for the ADP2106 (1.5 A)
V
1.2 V
1.5 V
1.8 V
2.5 V
3.3 V
Table 8. Minimum Inductor Value for Common Output
Voltage Options for the ADP2107 (2 A)
V
1.2 V
1.5 V
1.8 V
2.5 V
3.3 V
Table 9. Inductor Recommendations for the ADP2105/
ADP2106/ADP2107
Vendor
Sumida
Toko
Coilcraft
Cooper
Bussmann
OUT
OUT
OUT
2.7 V
1.67 μH
1.68 μH
2.02 μH
2.80 μH
3.70 μH
2.7 V
1.11 μH
1.25 μH
1.49 μH
2.08 μH
2.74 μH
2.7 V
0.83 μH
0.99 μH
1.19 μH
1.65 μH
2.18 μH
Small-Sized Inductors
(< 5 mm × 5 mm)
CDRH2D14, 3D16,
3D28
1069AS-DB3018,
1098AS-DE2812,
1070AS-DB3020
LPS3015, LPS4012,
DO3314
SD3110, SD3112,
SD3114, SD3118,
SD3812, SD3814
ADP2105/ADP2106/ADP2107
3.6 V
2.00 μH
2.19 μH
2.25 μH
2.80 μH
3.70 μH
3.6 V
2.33 μH
1.46 μH
1.50 μH
2.08 μH
2.74 μH
3.6 V
1.00 μH
1.09 μH
1.19 μH
1.65 μH
2.18 μH
V
V
V
IN
IN
IN
4.2 V
2.14 μH
2.41 μH
2.57 μH
2.80 μH
3.70 μH
4.2 V
2.43 μH
1.61 μH
1.71 μH
2.08 μH
2.74 μH
4.2 V
1.07 μH
1.21 μH
1.29 μH
1.65 μH
2.18 μH
Large-Sized Inductors
(> 5 mm × 5 mm)
CDRH4D18, 4D22,
4D28, 5D18, 6D12
D52LC, D518LC,
D62LCB
DO1605T
SD10, SD12, SD14, SD52
5.5 V
2.35 μH
2.73 μH
3.03 μH
3.41 μH
3.70 μH
5.5 V
1.56 μH
1.82 μH
2.02 μH
2.27 μH
2.74 μH
5.5 V
1.17 μH
1.36 μH
1.51 μH
1.70 μH
2.18 μH