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参数资料
| 型号： | LM3355MM-4.1/NOPB |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHED CAPACITOR REGULATOR, 1400 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封装： | MSOP-8 |
| 文件页数： | 9/10页 |
| 文件大小： | 209K |
| 代理商： | LM3355MM-4.1/NOPB |
Filter Capacitor Selection (Continued)
iii) Polymer Electrolytic
Polymer electrolytic is a third suitable technology. Polymer
capacitors provide some of the best features of both the
ceramic and the tantalum technologies. They provide very
low ESR values while still achieving high capacitance val-
ues. However, their ESR is still higher than the ceramics,
and their capacitance value is lower than the tantalums of
the same size. Polymers offer good frequency stability (com-
parable to ceramics) and good temperature stability (compa-
rable to tantalums). The Aluminum Polymer Electrolytics
offered by Cornell-Dubilier and Panasonic, and the POS-
CAPs offered by Sanyo fall under this category.
Table 1 compares the features of the three capacitor tech-
nologies.
TABLE 1. Comparison of Capacitor Technologies
Ceramic
Tantalum
Polymer
Electrolytic
ESR
Lowest
High
Low
Relative Height
Low for Small Values (<10 F); Taller for
Higher Values
Lowest
Low
Relative Footprint
Large
Small
Largest
Temperature Stability
X7R/X5R-Acceptable
Good
Frequency Stability
Good
Acceptable
Good
V
OUT Ripple Magnitude @ <50 mA
Low
High
Low
V
OUT Ripple Magnitude @ >100 mA
Low
Slightly Higher
Low
dv/dt of V
OUT Ripple @ All Loads
Lowest
High
Low
b) CAPACITOR SELECTION
i) Output Capacitor (C
OUT)
The output capacitor C
OUT directly affects the magnitude of
the output ripple voltage so C
OUT should be carefully se-
lected. The graphs titled V
OUT Ripple vs. COUT in the Typical
Performance Characteristics section show how the ripple
voltage magnitude is affected by the C
OUT value and the
capacitor technology. These graphs are taken at the gain at
which worst case ripple is observed. In general, the higher
the value of C
OUT, the lower the output ripple magnitude. At
lighter loads, the low ESR ceramics offer a much lower V
OUT
ripple than the higher ESR tantalums of the same value. At
higher loads, the ceramics offer a slightly lower V
OUT ripple
magnitude than the tantalums of the same value. However,
the dv/dt of the V
OUT ripple with the ceramics and polymer
electrolytics is much lower than the tantalums under all load
conditions. The tantalums are suggested for very low profile,
small size applications. The ceramics and polymer electro-
lytics are a good choice for low ripple, low noise applications
where size is less of a concern.
ii) Input Capacitor (C
IN)
The input capacitor C
IN directly affects the magnitude of the
input ripple voltage, and to a lesser degree the V
OUT ripple.
A higher value C
IN will give a lower VIN ripple. To optimize
low input and output ripple as well as size a 10 F polymer
electrolytic or ceramic, or 15 F tantalum capacitor is rec-
ommended. This will ensure low input ripple at 50 mA load
current. If lower currents will be used or higher input ripple
can be tolerated then a smaller capacitor may be used to
reduce the overall size of the circuit. The lower ESR ceram-
ics and polymer electrolytics achieve a lower V
IN ripple than
the higher ESR tantalums of the same value. Tantalums
make a good choice for small size, very low profile applica-
tions. The ceramics and polymer electrolytics are a good
choice for low ripple, low noise applications where size is
less of a concern. The 10 F polymer electrolytics are physi-
cally much larger than the 15 F tantalums and 10 F
ceramics.
iii) C
FIL
A 1 F, X7R ceramic capacitor should be connected to pin
C
FIL. This capacitor provides the filtering needed for the
internal supply rail of the LM3355.
Of the different capacitor technologies, a sample of vendors
that have been verified as suitable for use with the LM3355
are shown in Table 2.
TABLE 2. Capacitor Vendor Information
Manufacturer
Tel
Fax
Website
Ceramic
Taiyo-yuden
(408) 573-4150
(408) 573-4159
www.t-yuden.com
AVX
(803) 448-9411
(803) 448-1943
www.avxcorp.com
Sprague/Vishay
(207) 324-4140
(207) 324-7223
www.vishay.com
Tantalum
Nichicon
(847) 843-7500
(847) 843-2798
www.nichicon.com
Polymer Electrolytic
Cornell-Dubilier (ESRD)
(508) 996-8561
(508) 996-3830
www.cornell-dubilier.com
Sanyo (POSCAP)
(619) 661-6322
(619) 661-1055
www.sanyovideo.com
Thermal Protection
During output short circuit conditions, the LM3355 will draw
high currents causing a rise in the junction temperature.
On-chip thermal protection circuitry disables the charge
pump action once the junction temperature exceeds the
thermal trip point, and re-enables the charge pump when the
junction temperature falls back to a safe operating point.
LM3355
www.national.com
8
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相关代理商/技术参数 |
参数描述 |
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| LM3355MMX-4.1 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Regulated 50mA Buck-Boost Switched Capacitor DC/DC Converter |
| LM335A | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Precision Temperature Sensors |
| LM335AD | 功能描述:板上安装温度传感器 Precision 1 Deg Cel RoHS:否 制造商:Omron Electronics 输出类型:Digital 配置: 准确性:+/- 1.5 C, +/- 3 C 温度阈值: 数字输出 - 总线接口:2-Wire, I2C, SMBus 电源电压-最大:5.5 V 电源电压-最小:4.5 V 最大工作温度:+ 50 C 最小工作温度:0 C 关闭: 安装风格: 封装 / 箱体: 设备功能:Temperature and Humidity Sensor |
| LM335ADT | 功能描述:板上安装温度传感器 Precision 1 Deg Cel RoHS:否 制造商:Omron Electronics 输出类型:Digital 配置: 准确性:+/- 1.5 C, +/- 3 C 温度阈值: 数字输出 - 总线接口:2-Wire, I2C, SMBus 电源电压-最大:5.5 V 电源电压-最小:4.5 V 最大工作温度:+ 50 C 最小工作温度:0 C 关闭: 安装风格: 封装 / 箱体: 设备功能:Temperature and Humidity Sensor |
| LM335AH | 功能描述:板上安装温度传感器 RoHS:否 制造商:Omron Electronics 输出类型:Digital 配置: 准确性:+/- 1.5 C, +/- 3 C 温度阈值: 数字输出 - 总线接口:2-Wire, I2C, SMBus 电源电压-最大:5.5 V 电源电压-最小:4.5 V 最大工作温度:+ 50 C 最小工作温度:0 C 关闭: 安装风格: 封装 / 箱体: 设备功能:Temperature and Humidity Sensor |
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