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| 型号： | LT3470HDDB |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 0.2 A SWITCHING REGULATOR, PDSO8 |
| 封装： | 3 X 2 MM, 0.75MM INCH HEIGHT, MO-229WECD-1, PLASTIC, DFN-8 |
| 文件页数： | 3/20页 |
| 文件大小： | 256K |
| 代理商： | LT3470HDDB |
11
LT3470
3470fc
Ceramic Capacitors
Ceramic capacitors are small, robust and have very low
ESR. However, ceramic capacitors can cause problems
when used with the LT3470. Not all ceramic capacitors are
suitable. X5R and X7R types are stable over temperature
and applied voltage and give dependable service. Other
types, including Y5V and Z5U have very large temperature
and voltage coefficients of capacitance. In an application
circuit they may have only a small fraction of their nominal
capacitance resulting in much higher output voltage ripple
than expected.
Ceramic capacitors are piezoelectric. The LT3470’s switch-
ing frequency depends on the load current, and at light
loads the LT3470 can excite the ceramic capacitor at audio
frequencies, generating audible noise. Since the LT3470
operates at a lower current limit during Burst Mode
operation, the noise is typically very quiet to a casual ear.
If this audible noise is unacceptable, use a high perfor-
mance electrolytic capacitor at the output. The input
capacitor can be a parallel combination of a 2.2
F ceramic
capacitor and a low cost electrolytic capacitor.
A final precaution regarding ceramic capacitors concerns
the maximum input voltage rating of the LT3470. A ce-
ramic input capacitor combined with trace or cable induc-
tance forms a high quality (under damped) tank circuit. If
the LT3470 circuit is plugged into a live supply, the input
voltage can ring to twice its nominal value, possibly
exceeding the LT3470’s rating. This situation is easily
avoided; see the Hot-Plugging Safely section.
BOOST and BIAS Pin Considerations
Capacitor C3 and the internal boost Schottky diode (see
Block Diagram) are used to generate a boost voltage that
is higher than the input voltage. In most cases a 0.22
F
capacitor will work well. Figure 2 shows two ways to
arrange the boost circuit. The BOOST pin must be more
than 2.5V above the SW pin for best efficiency. For outputs
of 3.3V and above, the standard circuit (Figure 2a) is best.
For outputs between 2.5V and 3V, use a 0.47
F. For lower
output voltages the boost diode can be tied to the input
Table 3. Capacitor Vendors
Vendor
Phone
URL
Part Series
Comments
Panasonic
(714) 373-7366
www.panasonic.com
Ceramic,
Polymer,
EEF Series
Tantalum
Kemet
(864) 963-6300
www.kemet.com
Ceramic,
Tantalum
T494, T495
Sanyo
(408) 749-9714
www.sanyovideo.com
Ceramic,
Polymer,
POSCAP
Tantalum
Murata
(404) 436-1300
www.murata.com
Ceramic
AVX
www.avxcorp.com
Ceramic,
Tantalum
TPS Series
Taiyo Yuden
(864) 963-6300
www.taiyo-yuden.com
Ceramic
VIN
BOOST
LT3470
(2a)
(2b)
SW
C3
0.22
F
VIN
VOUT
VBOOST – VSW VOUT
MAX VBOOST VIN + VOUT
BIAS
GND
VIN
BOOST
LT3470
SW
BIAS
C3
0.22
F
VIN
VOUT
3470 F02
VBOOST – VSW VIN
MAX VBOOST 2VIN
GND
Figure 2. Two Circuits for Generating the Boost Voltage
APPLICATIO S I FOR ATIO
WU
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相关代理商/技术参数 |
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|---|---|
| LT3470HDDB#TRMPBF | 功能描述:IC REG BUCK ADJ 0.2A 8DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3470HDDB#TRPBF | 功能描述:IC REG BUCK ADJ 0.2A 8DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3470HTS8 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Micropower Buck Regulator with Integrated Boost and Catch Diodes |
| LT3470HTS8#PBF | 制造商:Linear Technology 功能描述:SP-SWREG/Monolithic, Cut Tape 300mA, 40V MicroPower Step-Down Regulator with Int |
| LT3470HTS8#TRMPBF | 功能描述:IC REG BUCK ADJ 0.2A TSOT23-8 RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
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