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參數(shù)資料
| 型號(hào)： | LM2853MH-1.5 |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 3A 550 kHz Synchronous SIMPLE SWITCHER Buck Regulator |
| 中文描述： | 5 A SWITCHING REGULATOR, 725 kHz SWITCHING FREQ-MAX, PDSO14 |
| 封裝： | TSSOP-14 |
| 文件頁(yè)數(shù)： | 8/12頁(yè) |
| 文件大小： | 620K |
| 代理商： | LM2853MH-1.5 |
Applications Information
(Continued)
Since it is undesirable for the power supply to start up in
current limit, a soft-start capacitor must be chosen to force
the LM2853 to start up in a more controlled fashion based on
the charging of the soft-start capacitance. In this example,
suppose a 3 ms start time is desired. Three time constants
are required for charging the soft-start capacitor to 95% of
the final reference voltage. So in this case RC = 1 ms. The
DAC resistor, R, is 450 k
so C can be calculated to be 2.2
nF. A 2.2 nF ceramic capacitor can be chosen to yield
approximately a 3 ms start-up time.
SOFT-START CAPACITOR (C
SS
) AND FAULT
CONDITIONS
Various fault conditions such as short circuit and UVLO of
the LM2853 activate internal circuitry designed to control the
voltage on the soft-start capacitor. For example, during a
short circuit current limit event, the output voltage typically
falls to a low voltage. During this time, the soft-start voltage
is forced to track the output so that once the short is re-
moved, the LM2853 can restart gracefully from whatever
voltage the output reached during the short circuit event. The
range of soft-start capacitors is therefore restricted to values
1 nF to 50 nF.
COMPENSATION
The LM2853 provides a highly integrated solution to power
supply design. The compensation of the LM2853, which is
type-three, is included on-chip. The benefit of integrated
compensation is straight-forward, simple power supply de-
sign. Since the output filter capacitor and inductor values
impact the compensation of the control loop, the range of L
,
C
O
and C
ESR
values is restricted in order to ensure stability.
OUTPUT FILTER VALUES
Table 1
details the recommended inductor and capacitor
ranges for the LM2853 that are suggested for various typical
output voltages. Values slightly different than those recom-
mended may be used, however the phase margin of the
power supply may be degraded. For best performance when
output voltage ripple is a concern, ESR values near the
minimum of the recommended range should be paired with
capacitance values near the maximum. If a minimum output
voltage ripple solution from a 5V input voltage is desired, a
6.8 μH inductor can be paired with a 220 μF (50 m
)
capacitor without degraded phase margin.
TABLE 1. Recommended L
O
and C
O
Values
V
OUT
(V)
0.8
0.8
VIN (V)
5
3.3
L
O
(μH)
C
O
(μF)
C
ESR
(m
)
Min
4.7
4.7
Max
6.8
4.7
Min
120
150
Max
220
220
Min
70
50
Max
100
100
1
1
5
4.7
4.7
6.8
4.7
120
150
220
220
70
50
100
100
3.3
1.2
1.2
5
4.7
4.7
6.8
4.7
120
120
220
220
70
60
100
100
3.3
1.5
1.5
5
4.7
4.7
6.8
4.7
120
120
220
220
70
60
100
100
3.3
1.8
1.8
5
4.7
4.7
6.8
4.7
120
100
220
220
70
70
120
120
3.3
2.5
2.5
5
4.7
4.7
6.8
4.7
120
100
220
220
70
80
150
150
3.3
3.0
3.0
5
4.7
4.7
6.8
4.7
120
100
220
220
70
80
150
150
3.3
3.3
5
4.7
6.8
120
220
70
150
L
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8
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| LM2853MH-1.8 | 3A 550 kHz Synchronous SIMPLE SWITCHER Buck Regulator |
| LM2853MH-2.5 | 3A 550 kHz Synchronous SIMPLE SWITCHER Buck Regulator |
| LM2853MH-3.0 | 3A 550 kHz Synchronous SIMPLE SWITCHER Buck Regulator |
| LM2853MH-3.3 | 3A 550 kHz Synchronous SIMPLE SWITCHER Buck Regulator |
| LM2853MHX-0.8 | 3A 550 kHz Synchronous SIMPLE SWITCHER Buck Regulator |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM2853MH-2.5 | 功能描述:直流/直流開(kāi)關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開(kāi)關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| LM2853MH-2.5/NOPB | 功能描述:直流/直流開(kāi)關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開(kāi)關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| LM2853MH-2.5/NOPB | 制造商:Texas Instruments 功能描述:DC/DC Converter IC |
| LM2853MH-3.0 | 功能描述:直流/直流開(kāi)關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開(kāi)關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| LM2853MH-3.0/NOPB | 功能描述:直流/直流開(kāi)關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開(kāi)關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
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