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參數(shù)資料
| 型號(hào)： | LM3351 |
| 廠商： | National Semiconductor Corporation |
| 元件分類： | 基準(zhǔn)電壓源/電流源 |
| 英文描述： | Switched Capacitor Voltage Converter |
| 中文描述： | 開關(guān)電容電壓轉(zhuǎn)換器 |
| 文件頁數(shù)： | 5/8頁 |
| 文件大?。?/td> | 265K |
| 代理商： | LM3351 |
Detailed Operation
(Continued)
STEP-UP APPLICATIONS NEED AN EXTRA DIODE
The LM3351 is biased from pin V
. Thus for step-up appli-
cations, an external Schottky diode (D1) is needed to supply
power to V
during startup (See Figure 1). Note that during
shutdown, this diode will provide a DC path from V
to V
.
The load may therefore continue to draw current from the in-
put voltage source. This Schottky diode is not required for
step-down applications (See Figure 2).
SHUTDOWN MODE
When ENABLE is a logic low (ground), the LM3351 enters a
low power shutdown mode. In this mode, all circuitry is dis-
abled and therefore, all switching action stops. During shut-
down, the current consumption drops to 250 nA (typical).
When ENABLE is a logic high, (i.e. 3.3V for step-up mode
and 5.0V for step-down mode), the LM3351 returns to nor-
mal operation.
Application Information
CAPACITOR SELECTION
The LM3351 requires four capacitors: an input bypass ca-
pacitor (connected between V
and ground), an output hold
capacitor (connected between V
and ground), and two
sampling capacitors (C1 and C2 in Figures 1, 2). 1.0 μF
(
±
20%) ceramic chip type capacitors are recommended for
all four capacitors. The usable operating frequency should
be greater than 5 MHz for all capacitors.
The output hold capacitor value determines the output ripple.
Increasing the value of the hold capacitor decreases the
ripple. The value of this capacitor (C
) can be calculated
(approximately) based on the output ripple (
V
out
) require-
ments from:
where I
load
is the load current and f
O
is the oscillator fre-
quency.
In order to ensure superior performance over the entire oper-
ating temperature range, capacitors made of X7R dielectric
material are suggested. However, capacitors made of other
dielectric materials that still meet the
±
20% specification
over the entire temperature range can also be used.
PRECAUTIONS
The LM3351 is not short circuit protected.
L
www.national.com
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|---|---|
| LM3351A WAF | 制造商:Texas Instruments 功能描述: |
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| LM3351MM | 功能描述:IC REG MULTI CONFIG 50MA 8-MSOP 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:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:1 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3.3V 輸入電壓:4.5 V ~ 24 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:125mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-6 包裝:Digi-Reel® 供應(yīng)商設(shè)備封裝:SOT-6 其它名稱:MAX1836EUT33#TG16DKR |
| LM3351MM/NOPB | 功能描述:IC REG MULTI CONFIG 50MA 8-MSOP 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:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:1 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3.3V 輸入電壓:4.5 V ~ 24 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:125mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-6 包裝:Digi-Reel® 供應(yīng)商設(shè)備封裝:SOT-6 其它名稱:MAX1836EUT33#TG16DKR |
| LM3351MM/NOPB | 制造商:Texas Instruments 功能描述:DC/DC Charge Pump Converter IC |
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