參數(shù)資料
型號(hào)： LT3470HDDB
廠商： LINEAR TECHNOLOGY CORP
元件分類： 穩(wěn)壓器
英文描述： 0.2 A SWITCHING REGULATOR, PDSO8
封裝： 3 X 2 MM, 0.75MM INCH HEIGHT, MO-229WECD-1, PLASTIC, DFN-8
文件頁(yè)數(shù)： 3/20頁(yè)
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
UU
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LT3470HDDB#TRMPBF 功能描述:IC REG BUCK ADJ 0.2A 8DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:50mA 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:10-MSOP 裸露焊盤
LT3470HDDB#TRPBF 功能描述:IC REG BUCK ADJ 0.2A 8DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:50mA 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:10-MSOP 裸露焊盤
LT3470HTS8 制造商:LINER 制造商全稱: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 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V，1.5V，1.8V，2.5V 輸入電壓:2.7 V ~ 20 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:50mA 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬）裸露焊盤 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:10-MSOP 裸露焊盤
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