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參數(shù)資料
| 型號： | LM2781 |
| 廠商： | National Semiconductor Corporation |
| 元件分類： | 基準電壓源/電流源 |
| 英文描述： | Ultra-Low Ripple Switched Capacitor Voltage Inverter |
| 中文描述： | 超低紋波電壓型逆變器開關電容 |
| 文件頁數(shù)： | 6/7頁 |
| 文件大小： | 162K |
| 代理商： | LM2781 |
Operation Description
(Continued)
OUTPUT RESISTANCE
Output resistance (R
OUT
) models the internal non-idealities
of a charge pump that result in droop in the output voltage.
The effect of output resistance on output voltage is ex-
pressed in the following equation:
V
OUT
= - [V
IN
- ( |I
OUT
| x R
OUT
)]
Output resistance is a function of the internal switch resis-
tance (R
) , flying capacitance (C1), flying capacitor
equivalent series resistance (ESR
), output capacitor ESR
(ESR
), and internal switching frequency (f
). When the
LM2781 operates as a single charge pump (C2 removed),
the output resistance can be approximated by the following
equation:
1 Fly Cap: R
OUT1
~= 2R
SW1
+[1/(f
SW
*C1)]+4ESR
C1
+ESR
Cout
R
is the sum of the ON resistance of the four internal
MOSFET switches of Charge Pump 1.
With both C1 and C2 in place, the double pumping topology
of the LM2781 cuts the output resistance in half:
2 Fly Caps: R
OUT2
~= 0.5xR
OUT1
Recommendations for minimizing output resistance include
increasing flying capacitance and minimizing output and fly-
ing capacitor ESR.
CAPACITOR SELECTION
Surface-mount multi-layer ceramic capacitors are recom-
mended for use with the LM2781. These capacitors are
small, inexpensive and have very low equivalent series re-
sistance (ESR,
<
15m
typ.). Tantalum capacitors, OS-CON
capacitors, and aluminum electrolytic capacitors generally
are not recommended for use with the LM2781 due to their
high ESR, as compared to ceramic capacitors.
For most applications, ceramic capacitors with X7R or X5R
temperature characteristic are preferred for use with the
LM2781. These capacitors have tight capacitance tolerance
(as good as
±
10%), hold their value over temperature (X7R:
±
15% over -55C to 125C; X5R:
±
15% over -55C to 85C),
and typically have little voltage coefficient.
Capacitors with Y5V and/or Z5U temperature characteristic
are generally not recommended for use with the LM2781.
These types of capacitors typically have wide capacitance
tolerance (+80%, -20%), vary significantly over temperature
(Y5V: +22%, -82% over -30C to +85C range; Z5U: +22%,
-56% over +10C to +85C range), and have poor voltage
coefficients. Under some conditions, a nominal 1μF Y5V or
Z5U capacitor could have a capacitance of only 0.1μF. Such
deviation would severely affect performance of the LM2781
circuit.
L
www.national.com
6
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LM2781TP | 制造商:Texas Instruments 功能描述:IC INVERTER SW CAP PUMP DUAL 2781 制造商:Texas Instruments 功能描述:-LIFETIME BUYS TIL 11/09 |
| LM2781TP/NOPB | 功能描述:IC REG SWITCHD CAP INV ADJ 8USMD RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關穩(wěn)壓器 系列:- 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝: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:- 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® 供應商設備封裝:SOT-6 其它名稱:MAX1836EUT33#TG16DKR |
| LM2781TPX | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Ultra-Low Ripple Switched Capacitor Voltage Inverter |
| LM2781TPX/NOPB | 功能描述:IC REG SWITCHD CAP INV ADJ 8USMD RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關穩(wěn)壓器 系列:- 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝: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:- 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® 供應商設備封裝:SOT-6 其它名稱:MAX1836EUT33#TG16DKR |
| LM2787 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Low Noise Regulated Switched Capacitor Voltage |
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