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參數(shù)資料
| 型號： | C3216X7R1E225K |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | N-Channel FET Synchronous Buck Regulator Controller for Low Output Voltages |
| 中文描述： | N溝道場效應管同步降壓穩(wěn)壓控制器輸出電壓低 |
| 文件頁數(shù)： | 9/22頁 |
| 文件大?。?/td> | 602K |
| 代理商： | C3216X7R1E225K |
Block Diagram
20049401
Application Information
THEORY OF OPERATION
The LM2727 is a voltage-mode, high-speed synchronous
buck regulator with a PWM control scheme. It is designed for
use in set-top boxes, thin clients, DSL/Cable modems, and
other applications that require high efficiency buck convert-
ers. It has power good (PWRGD), output shutdown (SD),
over voltage protection (OVP) and under voltage protection
(UVP). The over-voltage and under-voltage signals are OR
gated to drive the Power Good signal and a shutdown latch,
which turns off the high side gate and turns on the low side
gate if pulled low. Current limit is achieved by sensing the
voltage V
DS
across the low side FET. During current limit the
high side gate is turned off and the low side gate turned on.
The soft start capacitor is discharged by a 95μA source
(reducing the maximum duty cycle) until the current is under
control. The LM2737 does not latch off during UVP or OVP,
and uses the HIGH and LOW comparators for the power-
good function only.
START UP
When V
exceeds 4.2V and the enable pin EN sees a logic
high the soft start capacitor begins charging through an
internal fixed 10μA source. During this time the output of the
error amplifier is allowed to rise with the voltage of the soft
start capacitor. This capacitor, Css, determines soft start
time, and can be determined approximately by:
An application for a microprocessor might need a delay of
3ms, in which case C
would be 12nF. For a different
device, a 100ms delay might be more appropriate, in which
case C
would be 400nF. (390 10%) During soft start the
PWRGD flag is forced low and is released when the voltage
reaches a set value. At this point this chip enters normal
operation mode, the Power Good flag is released, and the
OVP and UVP functions begin to monitor Vo.
NORMAL OPERATION
While in normal operation mode, the LM2727/37 regulates
the output voltage by controlling the duty cycle of the high
side and low side FETs. The equation governing output
voltage is:
The PWM frequency is adjustable between 50kHz and
2MHz and is set by an external resistor, R
, between the
FREQ pin and ground. The resistance needed for a desired
frequency is approximately:
L
www.national.com
9
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相關代理商/技術參數(shù) |
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| C3216X7R1E225K/8 | 功能描述:CAP CER 2.2UF 25V 10% X7R 1206 RoHS:是 類別:電容器 >> 陶瓷 系列:C 標準包裝:4,000 系列:- 電容:1000pF 電壓 - 額定:50V 容差:±10% 溫度系數(shù):X7R 安裝類型:表面貼裝，MLCC 工作溫度:-55°C ~ 125°C 應用:自動 額定值:AEC-Q200 封裝/外殼:0805（2012 公制） 尺寸/尺寸:0.079" L x 0.047" W（2.00mm x 1.20mm） 高度 - 座高（最大）:- 厚度（最大）:- 引線間隔:- 特點:- 包裝:帶卷 (TR) 引線型:- |
| C3216X7R1E225K160AA | 制造商:TDK Innoveta 功能描述:Cap Ceramic 2.2uF 25V X7R 10% SMD 1206 125°C Plastic T/R 制造商:TDK 功能描述:CAP 2.2UF 25VDC X7R 10% SMD 1206 - Tape and Reel 制造商:TDK 功能描述:CAP CER 2.2UF 25V 10% X7R 1206 制造商:TDK 功能描述:C Series 1206 2.2 uF 25 V 10 % Tolerance X7R SMT Multilayer Ceramic Capacitor 制造商:TDK 功能描述:CAPACITOR CERAMIC, 2.2UF, 25V, X7R, 10%, 1206; Capacitance:2.2F; Capacitance Tolerance: 10%; Dielectric Characteristic:X7R; Voltage Rating:25V; Capacitor Case Style:1206 [3216 Metric]; Capacitor Terminals:SMD; No. of Pins:2 ;RoHS Compliant: Yes 制造商:TDK 功能描述:CAPACITOR CERAMIC, 2.2UF, 25V, X7R, 10%, 1206; Capacitance:2.2F; Capacitance Tolerance: 10%; Dielectric Characteristic:X7R; Voltage Rating:25V; Capacitor Case Style:1206 [3216 Metric]; Operating Temperature Min:-55C; No. of Pins:2;RoHS Compliant: Yes 制造商:TDK CORPORATION OF AMERICA 功能描述:Case:C3216, T.C:X7R, Voltage:1E, Cap Value:225, Tol:K, Thickness:1.6, E series: 3 制造商:TDK CORPORATION OF AMERICA 功能描述:CASE:C3216, T.C:X7R, VOLTAGE:1E, CAP VALUE:225, TOL:K, THICKNESS:1.6 |
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