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參數(shù)資料
| 型號： | MAX1742-MAX1842 |
| 廠商： | Maxim Integrated Products, Inc. |
| 元件分類： | 數(shù)字信號處理 |
| 英文描述： | Replaced by TMS320C6410 : Digital Signal Processor 40-PDIP 0 to 0 |
| 中文描述： | 1A/2.7A的1MHz，降壓型同步整流和內(nèi)部開關(guān)穩(wěn)壓器 |
| 文件頁數(shù)： | 13/16頁 |
| 文件大小： | 597K |
| 代理商： | MAX1742-MAX1842 |
M
1A/2.7A, 1MHz, Step-Down Regulators with
Synchronous Rectification and Internal Switches
______________________________________________________________________________________
13
The peak inductor current at full load is 1.125 x I
OUT
if
the above equation is used; otherwise, the peak current
is calculated by:
Choose an inductor with a saturation current at least as
high as the peak inductor current. The inductor you
select should exhibit low losses at your chosen operat-
ing frequency.
Capacitor Selection
The input filter capacitor reduces peak currents and
noise at the voltage source. Use a low-ESR and low-
ESL capacitor located no further than 5mm from IN.
Select the input capacitor according to the RMS input
ripple-current requirements and voltage rating:
where I
RIPPLE
= input RMS current ripple.
The output filter capacitor affects the output voltage rip-
ple, output load-transient response, and feedback loop
stability. For stable operation, the MAX1742/MAX1842
requires a minimum output ripple voltage of V
RIPPLE
≥
1% x V
OUT
.
The minimum ESR of the output capacitor should be:
Stable operation requires the correct output filter capaci-
tor. When choosing the output capacitor, ensure that:
Integrator Amplifier
An internal transconductance amplifier fine tunes the
output DC accuracy. A capacitor, C
COMP
, from COMP
to V
CC
compensates the transconductance amplifier.
For stability, choose C
COMP
= 470pF.
A large capacitor value maintains a constant average
output voltage but slows the loop response to changes
in output voltage. A small capacitor value speeds up
the loop response to changes in output voltage but
decreases stability. Choose the capacitor values that
result in optimal performance.
Soft-Start
Soft-start allows a gradual increase of the internal cur-
rent limit to reduce input surge currents at startup and
at exit from shutdown. A timing capacitor, C
SS
, placed
from SS to GND sets the rate at which the internal cur-
rent limit is changed. Upon power-up, when the device
comes out of undervoltage lockout (2.6V typ) or after
the
SHDN
pin is pulled high, a 4μA constant-current
source charges the soft-start capacitor and the voltage
on SS increases. When the voltage on SS is less than
approximately 0.7V, the current limit is set to zero. As
the voltage increases from 0.7V to approximately 1.8V,
the current limit is adjusted from 0 to the current-limit
threshold (see the
Electrical Characteristics
).The volt-
age across the soft-start capacitor changes with time
according to the equation:
The soft-start current limit varies with the voltage on the
soft-start pin, SS, according to the equation:
where I
LIMIT
is the current threshold from the
Electrical
Characteristics
.
SSI
V
V
V
I
LIMIT
SS
LIMIT
=
.
×
.
0 7
1 1
V
A
C
t
SS
SS
×
=
4
μ
C
t
V
FV
μ
s for the MAX
μ
OUT
OFF
OUT
≥
/
79
1842
C
t
V
FV
μ
s for the MAX
μ
OUT
OFF
OUT
≥
/
33
1742
ESR
L
t
OFF
%
1
>
I
I
V
V
V
V
RIPPLE
LOAD
OUT
IN
OUT
IN
=
(
)
I
I
V
t
L
PEAK
OUT
OUT
OFF
=
+
×
×
2
0.7V
1.8V
I
LIMIT
t
SHDN
0
0
0
V
SS
(V)
I
LIMIT
(A)
Figure 5. Soft-Start Current Limit over Time
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PDF描述 |
|---|---|
| MAX1742EEE | Replaced by TMS320C6410 : |
| MAX1843 | 2.7A, 1MHz, Low-Voltage, Step-Down Regulator with Internal Synchronous Rectification in QFN Package |
| MAX1843EGI | 2.7A, 1MHz, Low-Voltage, Step-Down Regulator with Internal Synchronous Rectification in QFN Package |
| MAX1845 | Dual, High-Efficiency, Step-Down Controller with Accurate Current Limit |
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| MAX17435ETG+ | 功能描述:電池管理 High f SMBus Battery Charger RoHS:否 制造商:Texas Instruments 電池類型:Li-Ion 輸出電壓:5 V 輸出電流:4.5 A 工作電源電壓:3.9 V to 17 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:VQFN-24 封裝:Reel |
| MAX17435ETG+T | 功能描述:電池管理 High f SMBus Battery Charger RoHS:否 制造商:Texas Instruments 電池類型:Li-Ion 輸出電壓:5 V 輸出電流:4.5 A 工作電源電壓:3.9 V to 17 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:VQFN-24 封裝:Reel |
| MAX17435EVKIT+ | 功能描述:電池管理 High Frequency SMBus Battery Charger RoHS:否 制造商:Texas Instruments 電池類型:Li-Ion 輸出電壓:5 V 輸出電流:4.5 A 工作電源電壓:3.9 V to 17 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:VQFN-24 封裝:Reel |
| MAX1744AUB | 功能描述:DC/DC 開關(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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