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參數(shù)資料
| 型號： | DS14287 |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | Timer or RTC |
| 英文描述： | 1 TIMER(S), REAL TIME CLOCK, PDIP24 |
| 封裝： | 0.740 INCH, ENCAPSULATED, DIP-24 |
| 文件頁數(shù)： | 4/16頁 |
| 文件大小： | 312K |
| 代理商： | DS14287 |
MAX774/MAX775/MAX776
inductor should not be so large that the peak current
never reaches the current limit. That is:
[V+(min) - VSW(max)] x 12s
L(max)
≤ _______________________________
ILIM(max)
This is only important if
VIN
1tOFF(min)
_______< — = ___________
VOUT
6tON(max)
More important is that the inductor not be so small that
the current rises much faster than the current-limit
comparator can respond. This would be wasteful and
reduce efficiency. Calculate the minimum inductor value
as follows:
[V+(max) - VSW(min)] x 0.3s
L(min)
≥ _______________________________
δ(I) x ILIM(min)
Where L is in H, 0.3s is an ample time for the com-
parator response, ILIM is the current limit (see the
Current-Sense Resistor section), and
δ(I) is the allow-
able percentage of overshoot. As an example, Figure
2's circuit uses a 3A peak current. If we allow a 15%
overshoot and 15V is the maximum input voltage, then
L(min) is 16H. The actual value of L above this limit
has minimal effect on this circuit's operation.
For highest efficiency, use a coil with low DC resistance.
Coils with 30m
or lower resistance are available. To min-
imize radiated noise, use a torroid, pot-core, or shielded-
bobbin inductor. Inductors with a ferrite core or equivalent
are recommended. Make sure that the inductor’s satura-
tion current rating is greater than ILIM(max).
Diode Selection
The ICs’ high switching frequencies demand a high-
speed rectifier. Schottky diodes such as the 1N5817 to
1N5822 families are recommended. Choose a diode
with an average current rating approximately equal to
or greater than ILIM (max) and a voltage rating higher
than VIN(max) + VOUT. For high-temperature applica-
tions, Schottky diodes may be inadequate due to their
high leakage currents; instead, high-speed silicon
diodes may be used. At heavy loads and high tempera-
ture, the benefits of a Schottky diode’s low forward volt-
age may outweigh the disadvantages of its high leak-
age current.
Current-Sense Resistor
The current-sense resistor limits the peak switch cur-
rent to 210mV/RSENSE, where RSENSE is the value of
the current-sense resistor, and 210mV is the current-
sense comparator threshold (see Current-Limit Trip
Level in the Electrical Characteristics).
To maximize efficiency and reduce the size and cost of
external components, minimize the peak current.
However, since the output current is a function of the
peak current, do not set the limit too low. See Figures
6–9 to determine the sense resistor, as well as the peak
current, for the required load current.
-5V/-12V/-15V or Adjustable, High-Efficiency,
Low IQ Inverting DC-to-DC Controllers
12
______________________________________________________________________________________
MAXIMUM
OUTPUT
CURRENT
(mA)
INPUT VOLTAGE (V)
0
500
1000
1500
2000
2500
34
5 6
7
8
9 10 11 12 13 14 15
VOUT = -5V
RSENSE = 0.05
RSENSE = 0.06
RSENSE = 0.08
RSENSE = 0.09
RSENSE = 0.07
MAX775-fig6
Figure 6. MAX774 Maximum Output Current vs. Input Voltage
(VOUT = -5V)
Figure 7. MAX775 Maximum Output Current vs. Input Voltage
(VOUT = -12V)
MAXIMUM
OUTPUT
CURRENT
(mA)
0
200
400
600
800
1000
9
INPUT VOLTAGE (V)
MAX775-FIG07
3
4
56
78
RSENSE = 0.05
RSENSE = 0.06
RSENSE = 0.07
RSENSE = 0.08
RSENSE = 0.09
VOUT = -12V
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| DS14287+ | 功能描述:實時時鐘 RoHS:否 制造商:Microchip Technology 功能:Clock, Calendar. Alarm RTC 總線接口:I2C 日期格式:DW:DM:M:Y 時間格式:HH:MM:SS RTC 存儲容量:64 B 電源電壓-最大:5.5 V 電源電壓-最小:1.8 V 最大工作溫度:+ 85 C 最小工作溫度: 安裝風格:Through Hole 封裝 / 箱體:PDIP-8 封裝:Tube |
| DS1-48-0001 | 功能描述:固定電感器 DS Storage choke 3.15A RoHS:否 制造商:AVX 電感:10 uH 容差:20 % 最大直流電流:1 A 最大直流電阻:0.075 Ohms 工作溫度范圍:- 40 C to + 85 C 自諧振頻率:38 MHz Q 最小值:40 尺寸:4.45 mm W x 6.6 mm L x 2.92 mm H 屏蔽:Shielded 端接類型:SMD/SMT 封裝 / 箱體:6.6 mm x 4.45 mm |
| DS1-48-0002 | 功能描述:固定電感器 DS Storage choke 4A RoHS:否 制造商:AVX 電感:10 uH 容差:20 % 最大直流電流:1 A 最大直流電阻:0.075 Ohms 工作溫度范圍:- 40 C to + 85 C 自諧振頻率:38 MHz Q 最小值:40 尺寸:4.45 mm W x 6.6 mm L x 2.92 mm H 屏蔽:Shielded 端接類型:SMD/SMT 封裝 / 箱體:6.6 mm x 4.45 mm |
| DS1-48-0003 | 制造商:Schurter Electronic Components 功能描述: |
| DS1-48-0004 | 制造商:Schurter Electronic Components 功能描述: |
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