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| 型号： | ADP1879-1.0-EVALZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 24/40页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL FOR ADP1879-1.0 |
| 标准包装： | 1 |
| 系列： | * |
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( ?? ?????? ? 0.6 V )
?? ?? = ?? ?? ×
?? ????????
??? ?? = ?? ?? × ?? ????????
≈
( ?? ???? ? ?? ?????? ) ?? ??????
?? =
×
ADP1878/ADP1879
APPLICATIONS INFORMATION
FEEDBACK RESISTOR DIVIDER
The required resistor divider network can be determined for a
given V OUT value because the internal band gap reference (V REF )
is fixed at 0.6 V. Selecting values for R T and R B determine the
minimum output load current of the converter. Therefore, for a
given value of R B , the R T value can be determined through the
following expression:
0.6 V
INDUCTOR SELECTION
The inductor value is inversely proportional to the inductor
ripple current. The peak-to-peak ripple current is given by
where K I is typically 0.33. 3
The equation for the inductor value is given by
where: ??? ?? × ?? ???? ?? ????
V IN is the high voltage input.
V OUT is the desired output voltage.
f SW is the controller switching frequency (300 kHz, 600 kHz, and
1.0 MHz).
When selecting the inductor, choose an inductor saturation
rating that is above the peak current level, and then calculate
the inductor current ripple (see the Valley Current-Limit
Data Sheet
Table 8. Recommended Inductors
L DCR I SAT Dimensions Model
(μH) (mΩ) (A) (mm) Manufacturer Number
0.12 0.33 55 10.2 × 7 Würth Elek. 744303012
0.22 0.33 30 10.2 × 7 Würth Elek. 744303022
0.47 0.8 50 14.2 × 12.8 Würth Elek. 744355147
0.72 1.65 35 10.5 × 10.2 Würth Elek. 744325072
0.9 1.6 32 14 × 12.8 Würth Elek. 744318120
1.2 1.8 25 10.5 × 10.2 Würth Elek. 744325120
1.0 3.8 16 10.2 × 10.2 Würth Elek. 7443552100
1.4 3.2 24 14 × 12.8 Würth Elek. 744318180
2.0 2.6 23 10.2 × 10.2 Würth Elek. 7443551200
0.8 27.5 Sumida CEP125U-0R8
OUTPUT RIPPLE VOLTAGE (ΔV RR )
The output ripple voltage is the ac component of the dc output
voltage during steady state. For a ripple error of 1.0%, the output
capacitor value needed to achieve this tolerance can be determined
using the following equation. (Note that an accuracy of 1.0% is
possible during steady state conditions only, not during load
transients.)
ΔV RR = (0.01) × V OUT
OUTPUT CAPACITOR SELECTION
The primary objective of the output capacitor is to facilitate the
reduction of the output voltage ripple; however, the output capacitor
also assists in the output voltage recovery during load transient
events. For a given load current step, the output voltage ripple
generated during this step event is inversely proportional to the
value chosen for the output capacitor. The speed at which the
output voltage settles during this recovery period depends on
52
50
48
46
44
42
40
38
ΔI = 50%
ΔI = 40%
where the crossover frequency (loop bandwidth) is set. This
crossover frequency is determined by the output capacitor, the
equivalent series resistance (ESR) of the capacitor, and the
compensation network.
1
?? ?????? = ??? ?? × ?
?
??? ????????
?? ?????? = 2 ×
36
34
32
30 ΔI = 33%
28
26
24
22
20
18
16
14
12
10
8
6 8 10 12 14 16 18 20 22 24 26 28 30
VALLEY CURRENT LIMIT (A)
Figure 81. Peak Inductor Current vs. Valley Current Limit for 33%, 40%, and
50% of Inductor Ripple Current
To calculate the small signal voltage ripple (output ripple voltage) at
the steady state operating point, use the following equation:
8 × ?? ???? × [ ??? ???????????? ? ( of × ?????? )]
where ESR is the equivalent series resistance ??? ?? the output
capacitors.
To calculate the output load step, use the following equation:
?? ???? × ???? that V ( ??? is × ?????? )
where Δ V DROOP is the amount ?????????? ? OUT ???????? allowed to ? deviate for
a given positive load current step (Δ I LOAD ).
Rev. B | Page 24 of 40
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| ADP1880ACPZ-R7 | 制造商:Analog Devices 功能描述: |
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