ADP2106-1.8-EVALZ Analog Devices Inc, ADP2106-1.8-EVALZ Datasheet - Page 22

• Manufacturer Part Number: ADP2106-1.8-EVALZ
• Description: BOARD EVAL FOR ADP2106-1.8
• Manufacturer: Analog Devices Inc

Specifications of ADP2106-1.8-EVALZ

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 1.8V
• Current - Output: 1.5A
• Voltage - Input: 2.7 ~ 5.5V
• Regulator Topology: Buck
• Frequency - Switching: 1.2MHz
• Board Type: Fully Populated
• Utilized Ic / Part: ADP2106
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

ADP2105/ADP2106/ADP2107
EFFICIENCY CONSIDERATIONS
Efficiency is the ratio of output power to input power. The high
efficiency of the ADP2105/ADP2106/ADP2107 has two distinct
advantages. First, only a small amount of power is lost in the dc-
to-dc converter package that reduces thermal constraints. Second,
the high efficiency delivers the maximum output power for the
given input power, extending battery life in portable applications.
There are four major sources of power loss in dc-to-dc
converters like the ADP2105/ADP2106/ADP2107:
•
•
•
•
Power Switch Conduction Losses
Power sw
current t
synchronous rectifier, which have intern
associated with them. The amount of power loss can be approx
mated by
where D = V
The internal resistance of the power switches increases with
temperature but decreases with higher input voltage. Figure 20
and Figure 21 show the change in R
whereas Figure 29 and Figure 30 show the change in
temperature for both power devices.
Inductor Losses
Inductor conduction lo
through the inductor, w
associated with it. Larger sized inducto
which can improve inductor conduction losses.
Inductor core losses are related to the magnetic permeability of
the core material. Because the ADP2105/ADP2106/ADP2107
are high switching frequency dc-to-dc converters, shielded ferrite
core materi
The
Switching Losses
Switching losses are associated with the current drawn by the
driver to turn on and turn off the power devices at the
switching frequency. Each time a power device gate is turned o
and turned off, the driver transfers a
supply to the gate a
The amount of power loss can by calculated by
where:
(C
f
SW
GATE − P
= 1.2 MHz, the switching frequency.
total amount of inductor power loss can be calculated by
P
P
P
Power switch conduction losses
Inductor losses
Switching losses
Transition losses
SW − COND
L
SW
= DCR × I
hrough the P-channel power switch and the N-
= (C
+ C
itch conduction losses are caused by the flow of
al is recommended for its low core losses and low EMI.
GATE − N
OUT
GATE − P
= [R
/V
OUT
IN
) ≈ 600 pF.
DS(ON) − P
nd then from the gate to ground.
+ C
.
2
+
sses are caused by the flow of current
GATE − N
hich has an internal resistance (DCR)
Core Losses
× D + R
) × V
DS(ON) − N
IN
DS(ON)
2
charge ΔQ from the input
× f
rs have smaller DCR,
SW
al resistances (R
vs. input voltag
× (1 − D)] × I
R
DS(ON)
channel
OUT
e,
DS(ON)
output
vs.
2
Rev. C | Page 22 of 36
)
i-
n
Transition Losses
Transition losses occur because the P-channel MOSFET power
switch cannot turn on or turn off instantaneously. At the middle o
an L
the in
power switch is half t
Transition losses increase with load current and input voltage
and occur twice for each switching cycle.
The amount of power loss can be calculated by
where t
(swi
THERM
In most applications, the ADP2105/ADP2106/AD
dissipate a lot of heat due to their high ef
applications with high
and high duty cycle, the heat dissipated in the package is large
enough that it can cause the junction temperature of the die to
exceed the maximum junction temperature of 125°C. Once the
junction temperature exceeds 140°C, the converter goes into
thermal shutdown. To prevent any permanent damage it recover
only after the junction temperature has decreased below 100°C.
Therefore, thermal analysis for the chosen a
is very important to guarantee reliable performa
conditions.
The junction temperature of the die is th
tempera ure of t e environment and the temperature rise o
package due to the power dissipation, as shown in the follo
equation:
where:
T
T
T
dissipation in the package.
The rise in temperature of the package is directly proportiona
to the power dissipation in the package. The proportionality
constant for this relationship is defined as the thermal resistance
from the junction of the die to the ambient temperature, as
shown in the following equation:
where:
T
P
θ
amb
JA
D
J
A
R
R
is the junction temperature.
is the ambient temperature.
is the rise in temperature of the package due to the power
is the rise in temperature of the package.
is the power dissipation in the package.
is the th
tch) node, and are both approximately 3
X (switch) nod ransition, the powe
ient temperatur
T = T + T
T
P
ductor current, while the source t
TRAN
J
R
ON
= θ
t
AL CONSIDERATIONS
and t
A
JA
=
ermal resistance from the junction of the die to the
×
V
2
IN
P
OFF
R
h
D
×
e t
are the rise time and fall time of the LX
I
OUT
e of the package.
he input voltage, resulting in power loss.
ambient temperature, low supply voltage,
×
(
t
ON
+
t
OFF
)
×
f
o drain voltage of the
SW
r switch is providing all
ficiency. However, in
e su
pplication solution
ns.
m of the ambient
nce over all
P2107 do not
wing
f the
l
s
f