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參數(shù)資料
| 型號(hào)： | MAX1745 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | High-Voltage, Step-Down DC-DC Controller in レMAX |
| 中文描述： | 高壓、降壓型DC-DC控制器，µMAX封裝 |
| 文件頁(yè)數(shù)： | 12/14頁(yè) |
| 文件大小： | 256K |
| 代理商： | MAX1745 |
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M
High-Voltage, Step-Down DC-DC
Controller in μMAX
12
______________________________________________________________________________________
Diode Selection
The MAX1744/MAX1745
’
s high switching frequency
demands a high-speed rectifier. Schottky diodes, such
as the 1N5817
–
1N5822 family or surface-mount equiva-
lents, are recommended. Ultra-high-speed rectifiers
with reverse recovery times around 50ns or faster
should be used for high output voltages, where the
increased forward drop causes less efficiency degra-
dation. Make sure that the diode
’
s peak current rating
exceeds the peak current limit set by R
SENSE
, and that
its breakdown voltage exceeds V
IN
. Schottky diodes
are preferred for heavy loads due to their low forward
voltage, especially in low-voltage applications. For
high-temperature applications, some Schottky diodes
may be inadequate due to their high leakage currents.
In such cases, ultra-high-speed rectifiers are recom-
mended, although a Schottky diode with a higher
reverse voltage rating can often provide acceptable
performance.
Capacitor Selection
Choose filter capacitors to service input and output
peak currents with acceptable voltage ripple. ESR in
the output capacitor is a major contributor to output rip-
ple, so low-ESR capacitors are recommended. Low-
ESR tantalum, polymer, or ceramic capacitors are best.
Low-ESR aluminum electrolytic capacitors are tolera-
ble, but standard aluminum electrolytic capacitors are
not recommended.
Voltage ripple is the sum of contributions from ESR and
the capacitor value:
For tantalum capacitors, the ripple is determined by the
ESR, but for ceramic capacitors, the ripple is mostly
due to the capacitance. Voltage ripple as a conse-
quence of ESR is approximated by:
The ripple due to the capacitance is approximately:
Estimate input and output capacitor values for given
voltage ripple as follows:
where I
L
is the change in inductor current.
These equations are suitable for initial capacitor selec-
tion; final values should be set by testing a prototype or
evaluation kit. When using tantalum capacitors, use
good soldering practices to prevent excessive heat
from damaging the devices and increasing their ESR.
Also, ensure that the tantalum capacitors
’
surge-current
ratings exceed the startup inrush and peak switching
currents.
Pursuing output ripple lower than the error compara-
tor
’
s hysteresis (0.6% of the output voltage) is not prac-
tical, since the MAX1744/MAX1745 will switch at slower
frequencies, increasing inductor ripple current thresh-
old. Choose an output capacitor with a working voltage
rating higher than the output voltage.
The input filter capacitor reduces peak currents drawn
from the power source and reduces noise and voltage
C
LI
V
C
LI
V
V
V
V
IN
L
RIPPLECIN IN
,
OUT
L
RIPPLECOUT OUT
,
IN
IN
OUT
=
=
1
2
2
1
2
2
V
LI
2CV
RIPPLE,C
PEAK
O
≈
2
V
RIPPLE,ESR
≈
(
)
R
ESR
Ip p
V
RIPPLE
≈
+
,
,
V
V
RIPPLEESR
RIPPLEC
Table 1. Component Suppliers
COMPANY
COUNTRY
PHONE
803-946-0690
or
800-282-4975
847-639-6400
516-241-7876
402-564-3131
408-986-0424
FAX
AVX
USA
803-626-3123
Coilcraft
Coiltronics
Dale/Vishay
Kemet
USA
USA
USA
USA
847-639-1469
516-241-9339
402-563-6418
408-986-1442
Inter nati onal
Recti i er
USA
310-322-3331
310-322-3332
IRC
Motorola
USA
USA
512-992-7900
602-303-5454
512-992-3377
602-994-6430
Nichicon
USA
Japan
847- 843- 7500
81- 7- 5231- 8461
847-843-2798
81-7-5256-4158
Nihon
USA
Japan
805- 867- 2555
81- 3- 3494- 7411
805-867-2698
81-3-3494-7414
Sanyo
USA
Japan
619- 661- 6835
81- 7- 2070- 6306
619-661-1055
81-7-2070-1174
408-988-8000
or
800-554-5565
603-224-1961
Siliconix
USA
408-970-3950
Sprague
USA
603-224-1430
Sumida
USA
Japan
847- 956- 0666
81- 3- 3607- 5111
847-956-0702
81-3-3607-5144
United
Chemi-Con
USA
714-255-9500
714-255-9400
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| MAX1745EUB | High-Voltage, Step-Down DC-DC Controller in レMAX |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX1745AUB | 功能描述:DC/DC 開(kāi)關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| MAX1745AUB+ | 功能描述:DC/DC 開(kāi)關(guān)控制器 Step-Down DC/DC Controller RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| MAX1745AUB+T | 功能描述:DC/DC 開(kāi)關(guān)控制器 Step-Down DC/DC Controller RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| MAX1745AUB-T | 功能描述:DC/DC 開(kāi)關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| MAX1745EUB | 功能描述:DC/DC 開(kāi)關(guān)控制器 Step-Down DC/DC Controller RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
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