ADP5043 Analog Devices, ADP5043 Datasheet - Page 21

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ADP5043

Manufacturer Part Number
ADP5043
Description
Micro-PMU with 0.8 A Buck, 300 mA LDO, Supervisory, Watchdog, and Manual Reset
Manufacturer
Analog Devices
Datasheet

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Part Number
Manufacturer
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Part Number:
ADP5043ACPZ-1-R7
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11 308
Data Sheet
APPLICATIONS INFORMATION
BUCK EXTERNAL COMPONENT SELECTION
Trade-offs between performance parameters such as efficiency
and transient response are made by varying the choice of
external components in the applications circuit, as shown in
Figure 48.
Inductor
The high switching frequency of the buck regulator of the
ADP5043 allows for the selection of small chip inductors. For
best performance, use inductor values between 0.7 μH and
3 μH. Suggested inductors are shown in Table 11.
The peak-to-peak inductor current ripple is calculated using
the following equation:
where:
f
L is the inductor value.
The minimum dc current rating of the inductor must be greater
than the inductor peak current. The inductor peak current is
calculated using the following equation:
Table 11. Suggested 1.0 μH Inductors
Vendor
Murata
Murata
Taiyo Yuden
Coilcraft
TDK
Coilcraft
Toko
Inductor conduction losses are caused by the flow of current
through the inductor, which has an associated internal dc
resistance (DCR). Larger sized inductors have smaller DCR,
which may decrease inductor conduction losses. Inductor core
losses are related to the magnetic permeability of the core material.
SW
is the switching frequency.
I
I
RIPPLE
PEAK
=
=
ADP5043
I
LOAD
Model
LQM2MPN1R0NG0B
LQM18FN1R0M00B
CBMF1608T1R0M
EPL2014-102ML
GLFR1608T1R0M-LR
0603LS-102
MDT2520-CN
V
VIN1
V
OUT
Figure 48. Typical Applications Circuit
CC
VOUT1
VOUT2
nRSTO
V
(
WDI1
WDI2
MAX
IN
×
(
×
V
)
f
IN
+
SW
I
RIPPLE
×
V
2
L
OUT
)
Dimensions
(mm)
2.0 × 1.6 × 0.9
1.6 × 0.8 × 0.8
1.6 × 0.8 × 0.8
2.0 × 2.0 × 1.4
1.6 × 0.8 × 0.8
1.8 × 1.69 × 1.1
2.5 × 2.0 × 1.2
MICROPROCESSOR
VCORE
VDDIO
RESET
I/O
I/O
I
(mA)
1400
150
290
900
230
400
1350
SAT
Rev. A | Page 21 of 32
DCR
(mΩ)
85
26
90
59
80
81
85
Because the buck is a high switching frequency dc-to-dc converter,
shielded ferrite core material is recommended for its low core
losses and low EMI.
Output Capacitor
Higher output capacitor values reduce the output voltage
ripple and improve load transient response. When choosing
the capacitor value, it is also important to account for the loss
of capacitance due to output voltage dc bias.
Ceramic capacitors are manufactured with a variety of dielec-
trics, each with a different behavior over temperature and
applied voltage. Capacitors must have a dielectric adequate
to ensure the minimum capacitance over the necessary tem-
perature range and dc bias conditions. X5R or X7R dielectrics
with a voltage rating of 6.3 V or 10 V are highly recommended
for best performance. Y5V and Z5U dielectrics are not
recommended for use with any dc-to-dc converter because
of their poor temperature and dc bias characteristics.
The worst-case capacitance accounting for capacitor variation
over temperature, component tolerance, and voltage is calcu-
lated using the following equation:
where:
C
TEMPCO is the worst-case capacitor temperature coefficient.
TOL is the worst-case component tolerance.
In this example, the worst-case temperature coefficient (TEMPCO)
over −40°C to +85°C is assumed to be 15% for an X5R dielectric.
The tolerance of the capacitor (TOL) is assumed to be 10%,
and C
Substituting these values in the equation yields
To guarantee the performance of the buck regulator, it is
imperative that the effects of dc bias, temperature, and
tolerances on the behavior of the capacitors be evaluated
for each application.
EFF
is the effective capacitance at the operating voltage.
C
C
OUT
EFF
EFF
12
10
8
6
4
2
0
0
= C
= 9.2481 μF × (1 − 0.15) × (1 − 0.1) = 7.0747 μF
is 9.2481 μF at 1.8 V, as shown in Figure 49.
OUT
Figure 49. Typical Capacitor Performance
× (1 − TEMPCO) × (1 − TOL)
1
2
DC BIAS VOLTAGE (V)
3
4
5
ADP5043
6

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