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參數(shù)資料
| 型號(hào)： | LTC1435IG#TRPBF |
| 廠(chǎng)商： | LINEAR TECHNOLOGY CORP |
| 元件分類(lèi)： | 穩(wěn)壓器 |
| 英文描述： | High Efficiency Low Noise Synchronous Step-Down Switching Regulator |
| 中文描述： | 2 A SWITCHING CONTROLLER, 400 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | 0.209 INCH, PLASTIC, SSOP-16 |
| 文件頁(yè)數(shù)： | 2/20頁(yè) |
| 文件大?。?/td> | 338K |
| 代理商： | LTC1435IG#TRPBF |
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10
LTC1435
APPLICATIONS INFORMATION
WU
U
where
δ is the temperature dependency of RDS(ON) and k
is a constant inversely related to the gate drive current.
Both MOSFETs have I2R losses while the topside
N-channel equation includes an additional term for tran-
sition losses, which are highest at high input voltages.
For VIN < 20V the high current efficiency generally im-
proves with larger MOSFETs, while for VIN > 20V the
transition losses rapidly increase to the point that the use
of a higher RDS(ON) device with lower CRSS actual pro-
vides higher efficiency. The synchronous MOSFET losses
are greatest at high input voltage or during a short circuit
when the duty cycle in this switch is nearly 100%. Refer
to the Foldback Current Limiting section for further
applications information.
The term (1 +
δ) is generally given for a MOSFET in the
form of a normalized RDS(ON) vs Temperature curve, but
δ = 0.005/°C can be used as an approximation for low
voltage MOSFETs. CRSS is usually specified in the MOSFET
characteristics. The constant k = 2.5 can be used to
estimate the contributions of the two terms in the main
switch dissipation equation.
The Schottky diode D1 shown in Figure 1 conducts during
the dead-time between the conduction of the two large
power MOSFETs. This prevents the body diode of the
bottom MOSFET from turning on and storing charge
during the dead-time, which could cost as much as 1% in
efficiency. A 1A Schottky is generally a good size for 3A
regulators.
CIN and COUT Selection
In continuous mode, the source current of the top
N-channel MOSFET is a square wave of duty cycle VOUT/
VIN. To prevent large voltage transients, a low ESR input
capacitor sized for the maximum RMS current must be
used. The maximum RMS capacitor current is given by:
C
required
IN
II
VV
V
RMS
MAX
OUT
IN
OUT
IN
≈
()
[]12/
This formula has a maximum at VIN = 2VOUT, where
IRMS = IOUT/2. This simple worst-case condition is com-
monly used for design because even significant deviations
do not offer much relief. Note that capacitor manufacturer’s
ripple current ratings are often based on only 2000 hours
of life. This makes it advisable to further derate the
capacitor or to choose a capacitor rated at a higher
temperature than required. Several capacitors may also be
paralleled to meet size or height requirements in the
design. Always consult the manufacturer if there is any
question.
The selection of COUT is driven by the required effective
series resistance (ESR). Typically, once the ESR require-
ment is satisfied the capacitance is adequate for filtering.
The output ripple (
VOUT) is approximated by:
V
I ESR
fC
OUT
L
OUT
≈+
1
4
where f = operating frequency, COUT = output capacitance
and
IL= ripple current in the inductor. The output ripple
is highest at maximum input voltage since
IL increases
with input voltage. With
IL = 0.4IOUT(MAX) the output
ripple will be less than 100mV at max VIN assuming:
COUT required ESR < 2RSENSE
Manufacturers such as Nichicon, United Chemicon and
Sanyo should be considered for high performance through-
hole capacitors. The OS-CON semiconductor dielectric
capacitor available from Sanyo has the lowest ESR(size)
product of any aluminum electrolytic at a somewhat
higher price. Once the ESR requirement for COUT has been
met, the RMS current rating generally far exceeds the
IRIPPLE(P-P) requirement.
In surface mount applications multiple capacitors may
have to be paralleled to meet the ESR or RMS current
handling requirements of the application. Aluminum elec-
trolytic and dry tantalum capacitors are both available in
surface mount configurations. In the case of tantalum, it is
critical that the capacitors are surge tested for use in
switching power supplies. An excellent choice is the AVX
TPS series of surface mount tantalum, available in case
heights ranging from 2mm to 4mm. Other capacitor types
include Sanyo OS-CON, Nichicon PL series and Sprague
593D and 595D series. Consult the manufacturer for other
specific recommendations.
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相關(guān)代理商/技術(shù)參數(shù) |
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| LTC1435IS | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC RoHS:否 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱(chēng):LM1771SSDX |
| LTC1435IS#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱(chēng):LM1771SSDX |
| LTC1435IS#TR | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Sync Step Down 3.5V to 36V Input 16-Pin SOIC N T/R |
| LTC1435IS#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱(chēng):LM1771SSDX |
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