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| 型號(hào)： | LM2575HVN-ADJ |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SIMPLE SWITCHER 1A Step-Down Voltage Regulator |
| 中文描述： | 3.2 A SWITCHING REGULATOR, 63 kHz SWITCHING FREQ-MAX, PDIP16 |
| 封裝： | PLASTIC, DIP-16 |
| 文件頁(yè)數(shù)： | 8/12頁(yè) |
| 文件大?。?/td> | 195K |
| 代理商： | LM2575HVN-ADJ |
www.ti.com
Input Capacitor (C
IN
)
For stability concerns, an input bypass capacitor (electrolytic, C
IN
≥
47
μ
F) needs to be located as close as
possible to the regulator. For operating temperatures below –25
°
C, C
IN
may need to be larger in value. In
addition, since most electrolytic capacitors have decreasing capacitances and increasing ESR as temperature
drops, adding a ceramic or solid tantalum capacitor in parallel increases the stability in cold temperatures.
I
C,RMS
1.2(t
on
T) I
LOAD
, where:
V
OUT
V
IN
|V
OUT
|
(|V
OUT
|
t
on
T
{buck regulator}, and
t
on
T
V
IN
){buckboost regulator}
Output Capacitor (C
OUT
)
For both loop stability and filtering of ripple voltage, an output capacitor also is required, again in close proximity
to the regulator. For best performance, low-ESR aluminum electrolytics are recommended, although standard
aluminum electrolytics may be adequate for some applications. Based on the following equation:
Output Ripple Voltage = (ESR of C
OUT
)
×
(inductor ripple current)
Output ripple of 50 mV to 150 mV typically can be achieved with capacitor values of 220
μ
F to 680
μ
F. Larger
C
OUT
can reduce the ripple 20 mV to 50 mV peak-to-peak. To improve further on output ripple, paralleling of
standard electrolytic capacitors may be used. Alternatively, higher-grade capacitors such as “high frequency”,
“l(fā)ow inductance”, or “l(fā)ow ESR” can be used.
Catch Diode
As with other external components, the catch diode should be placed close to the output to minimize unwanted
noise. Schottky diodes have fast switching speeds and low forward voltage drops and, thus, offer the best
performance, especially for switching regulators with low output voltages (V
OUT
< 5 V). If a high-efficiency,
fast-recovery, or ultra-fast-recovery diode is used in place of a Schottky, it should have a soft recovery (versus
abrupt turn-off characteristics) to avoid the chance of causing instability and EMI. Standard 50-/60-Hz diodes,
such as the 1N4001 or 1N5400 series, are NOT suitable.
Inductor
Proper inductor selection is key to the performance-switching power-supply designs. One important factor to
consider is whether the regulator will be used in continuous (inductor current flows continuously and never drops
to zero) or in discontinuous mode (inductor current goes to zero during the normal switching cycle). Each mode
has distinctively different operating characteristics and, therefore, can affect the regulator performance and
requirements. In many applications, the continuous mode is the preferred mode of operation, since it offers
greater output power with lower peak currents, and also can result in lower output ripple voltage. The advantages
of continuous mode of operation come at the expense of a larger inductor required to keep inductor current
continuous, especially at low output currents and/or high input voltages.
LM2575
1-A SIMPLE STEP-DOWN SWITCHING VOLTAGE REGULATOR
SLVS569D–JANUARY 2005–REVISED JULY 2005
APPLICATION INFORMATION (continued)
To extend the capacitor operating lifetime, the capacitor RMS ripple current rating should be:
The following should be taken into account when selecting C
OUT
:
At cold temperatures, the ESR of the electrolytic capacitors can rise dramatically (typically 3
×
nominal value
at –25
°
C). Because solid tantalum capacitors have significantly better ESR specifications at cold
temperatures, they should be used at operating temperature lower than –25
°
C. As an alternative, tantalums
also can be paralleled to aluminum electrolytics and should contribute 10% to 20% to the total capacitance.
Low ESR for C
is desirable for low output ripple. However, the ESR should be greater than 0.05
to
avoid the possibility of regulator instability. Hence, a sole tantalum capacitor used for C
OUT
is most
susceptible to this occurrence.
The capacitor’s ripple current rating of 52 kHz should be at least 50% higher than the peak-to-peak inductor
ripple current.
8
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| LM2575HVN-ADJ/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 |
| LM2575HVS-12 | 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 |
| LM2575HVS-12/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 |
| LM2575HVS-12/NOPB | 制造商:Texas Instruments 功能描述:DC/DC Converter IC |
| LM2575HVS-15 | 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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