Analog Devices ADP1660 Evaluation Board ADP1660CB-EVALZ ADP1660CB-EVALZ Ficha De Dados
Códigos do produto
ADP1660CB-EVALZ
ADP1660
Data Sheet
Rev. 0 | Page 24 of 28
APPLICATIONS INFORMATION
EXTERNAL COMPONENT SELECTION
Selecting the Inductor
boost converter increases the battery voltage to
allow driving of two LEDs when the forward voltage of the LEDs
is higher than the battery voltage minus 2× the current source
headroom voltage. This allows the converter to regulate the LED
current over the entire battery voltage range and with a wide
variation of LED forward voltages.
The inductor saturation current should be greater than the sum
of the dc input current and half the inductor ripple current. A
reduction in the effective inductance due to saturation increases
the inductor ripple current. Table 28 provides a list of suggested
is higher than the battery voltage minus 2× the current source
headroom voltage. This allows the converter to regulate the LED
current over the entire battery voltage range and with a wide
variation of LED forward voltages.
The inductor saturation current should be greater than the sum
of the dc input current and half the inductor ripple current. A
reduction in the effective inductance due to saturation increases
the inductor ripple current. Table 28 provides a list of suggested
inductors.
Table 28. Suggested Inductors
Vendor
Value
(µH)
Part No.
DCR
(mΩ)
I
SAT
(A)
Dimensions
L × W × H (mm)
Toko
1.0
FDSD0312
43
4.5
3.0 × 3.0 × 1.2
Toko
1.0
DFE2520
50
3.4
2.5 × 2.0 × 1.0
Coilcraft 1.0
XFL3010
43
2.4
3.0 × 3.0 × 1.0
Murata
1.0
LQM32P_G0 48
3
3.2 × 2.5 × 1.0
FDK
1.0
MIP3226D
40
3
3.2 × 2.6 × 1.0
Selecting the Input Capacitor
The
requires an input bypass capacitor to supply tran-
sient currents while maintaining constant input and output
voltages. The input capacitor carries the input ripple current,
allowing the input power source to supply only the dc current.
Increased input capacitance reduces the amplitude of the switching
frequency ripple on the battery. Due to the dc bias characteristics
of ceramic capacitors, the recommended capacitor is a 10.0 µF,
voltages. The input capacitor carries the input ripple current,
allowing the input power source to supply only the dc current.
Increased input capacitance reduces the amplitude of the switching
frequency ripple on the battery. Due to the dc bias characteristics
of ceramic capacitors, the recommended capacitor is a 10.0 µF,
6.3 V, X5R/X7R ceramic capacitor.
Higher input capacitor values help to reduce the input voltage
Higher input capacitor values help to reduce the input voltage
ripple and improve transient response.
To minimize supply noise, place the input capacitor as close to
the VIN pin of the
To minimize supply noise, place the input capacitor as close to
the VIN pin of the
as possible. A low ESR capacitor is
required. Table 29 provides a list of suggested input and output
capacitors.
Table 29. Suggested Input and Output Capacitors
Vendor
Value
Part No.
Dimensions
L × W × H (mm)
Murata
10 µF, 6.3 V
GRM188R60J106ME47 1.6 × 0.8 × 0.8
TDK
10 µF, 6.3 V
C1608JB0J106K
1.6 × 0.8 × 0.8
Taiyo
Yuden
10 µF, 6.3 V
JMK107BJ106MA
1.6 × 0.8 × 0.8
Selecting the Output Capacitor
The output capacitor maintains the output voltage and supplies
the LED current during the on period of the N-FET power
switch. It also stabilizes the loop. The recommended capacitor
the LED current during the on period of the N-FET power
switch. It also stabilizes the loop. The recommended capacitor
is a 10.0 µF, 6.3 V, X5R/X7R ceramic capacitor (see Table 29).
Note that dc bias characterization data is available from capacitor
manufacturers and should be taken into account when selecting
input and output capacitors. Capacitors of 6.3 V or 10 V are best
manufacturers and should be taken into account when selecting
input and output capacitors. Capacitors of 6.3 V or 10 V are best
for most designs.
Higher output capacitor values reduce the output voltage ripple
and improve load transient response. When selecting an output
capacitor value, it is also important to account for the loss of
Higher output capacitor values reduce the output voltage ripple
and improve load transient response. When selecting an output
capacitor value, it is also important to account for the loss of
capacitance due to output voltage dc bias.
Ceramic capacitors have a variety of dielectrics, each with different
behavior over temperature and applied voltage. Capacitors must
have a dielectric that ensures the minimum capacitance over the
necessary temperature range and dc bias conditions. X5R or X7R
dielectrics with a voltage rating of 6.3 V or 10 V are recommended
for best performance. Y5V and Z5U dielectrics are not recom-
mended 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 calculated
Ceramic capacitors have a variety of dielectrics, each with different
behavior over temperature and applied voltage. Capacitors must
have a dielectric that ensures the minimum capacitance over the
necessary temperature range and dc bias conditions. X5R or X7R
dielectrics with a voltage rating of 6.3 V or 10 V are recommended
for best performance. Y5V and Z5U dielectrics are not recom-
mended 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 calculated
using the following equation:
C
EFF
= C
OUT
× (1 − TEMPCO) × (1 − TOL)
where:
C
EFF
is the effective capacitance at the operating voltage.
TEMPCO is the worst-case capacitor temperature coefficient.
TOL is the worst-case component tolerance.
For example, a 10 μF, X5R capacitor has the following
For example, a 10 μF, X5R capacitor has the following
characteristics:
TEMPCO from −40°C to +85°C is 15%.
TOL is 10%.
TEMPCO from −40°C to +85°C is 15%.
TOL is 10%.
C
OUT
at V
OUT (MAX)
= 5 V is 3 μF (see Figure 31).
10
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
6.30
5.04
3.78
2.52
DC BIAS VOLTAGE (V)
CA
P
ACI
T
ANCE
CHANG
E
(
%)
1.26
0
1
1018-
026
Figure 31. DC Bias Characteristic of a 10 μF, 6.3 V Ceramic Capacitor
Substituting these values in the equation yields
C
EFF
= 3 μF × (1 − 0.15) × (1 − 0.1) = 2.3 μF
The effective capacitance needed for stability, which includes
temperature and dc bias effects, is 3.0 μF.