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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： | 8/10页 |
| 文件大小： | 209K |
| 代理商： | LM3355MM-4.1/NOPB |
Applications Information
Operating Principle
The LM3355 is designed to provide a step-up/step-down
voltage regulation in battery powered systems. It combines
switched capacitor circuitry, reference, comparator, and
shutdown logic in a single 10-pin MSOP package. The
LM3355 can provide a regulated voltage between 1.8V and
4.1V from an input voltage between 2.5V and 5.5V. It can
supply a load current up to 50 mA.
As shown in Figure 1, the LM3355 employs two feedback
loops to provide regulation in the most efficient manner
possible. The first loop is from V
OUT through the comparator
COMP, the AND gate G
1, the phase generator, and the
switch array. The comparator’s output is high when V
OUT is
less than the reference V
REF. Regulation is provided by
gating the clock to the switch array. In this manner, charge is
transferred to the output only when needed. The second
loop controls the gain configuration of the switch array. This
loop consists of the comparator, the digital control block, the
phase generator, and the switch array. The digital control
block computes the most efficient gain from a set of five
gains based on inputs from the A/D and the comparator. The
gain signal is sent to the phase generator which then sends
the appropriate timing and configuration signals to the switch
array. This dual loop provides regulation over a wide range of
loads efficiently.
Since efficiency is automatically optimized, the curves for
V
OUT vs. VIN and Efficiency vs. VIN in the Typical Perfor-
mance Characteristics section exhibit small variations. The
reason is that as input voltage or output load changes, the
digital control loops are making decisions on how to optimize
efficiency. As the switch array is reconfigured, small varia-
tions in output voltage and efficiency result. In all cases
where these small variations are observed, the part is oper-
ating correctly; minimizing output voltage changes and opti-
mizing efficiency.
Charge Pump Capacitor Selection
A 0.33 F ceramic capacitor is suggested for C1 and C2. To
ensure proper operation over temperature variations, an
X7R dielectric material is recommended.
Filter Capacitor Selection
a) CAPACITOR TECHNOLOGIES
The three major technologies of capacitors that can be used
as filter capacitors for LM3355 are: i) tantalum, ii) ceramic
and iii) polymer electrolytic technologies.
i) Tantalum
Tantalum capacitors are widely used in switching regulators.
Tantalum capacitors have the highest CV rating of any tech-
nology; as a result, high values of capacitance can be ob-
tained in relatively small package sizes. It is also possible to
obtain high value tantalum capacitors in very low profile
(<1.2 mm) packages. This makes the tantalums attractive
for low-profile, small size applications. Tantalums also pos-
sess very good temperature stability; i.e., the change in the
capacitance value, and impedance over temperature is rela-
tively small. However, the tantalum capacitors have relatively
high ESR values which can lead to higher voltage ripple and
their frequency stability (variation over frequency) is not very
good, especially at high frequencies (>1 MHz).
ii) Ceramic
Ceramic capacitors have the lowest ESR of the three tech-
nologies and their frequency stability is exceptionally good.
These characteristics make the ceramics an attractive
choice for low ripple, high frequency applications. However,
the temperature stability of the ceramics is bad, except for
the X7R and X5R dielectric types. High capacitance values
(>1 F) are achievable from companies such as Taiyo-
yuden which are suitable for use with regulators. Ceramics
are taller and larger than the tantalums of the same capaci-
tance value.
20021903
FIGURE 1. Block Diagram
LM3355
www.national.com
7
相关PDF资料 |
PDF描述 |
|---|---|
| LM3355MMX-4.1/NOPB | SWITCHED CAPACITOR REGULATOR, 1400 kHz SWITCHING FREQ-MAX, PDSO8 |
| LM3361AMX | FM, AUDIO SINGLE CHIP RECEIVER, PDSO16 |
| LM3361AM | FM, AUDIO SINGLE CHIP RECEIVER, PDSO16 |
| LM336Z-2.5B | 1-OUTPUT TWO TERM VOLTAGE REFERENCE, 2.49 V, PBCY3 |
| LM3460M5X-1.5/NOPB | 1-OUTPUT THREE TERM VOLTAGE REFERENCE, 1.5 V, PDSO5 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| 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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