Datasheet > AN701

AN701

更新时间： 2022-11-25 11:11:34

品牌	Logo	应用领域
威世 - VISHAY		转换器开关控制器
页数	文件大小	规格书
20页	1116K
描述
Designing High-Frequency DC-to-DC Converters With the Si9114A Switchmode Controller

阅读下载

中文翻译

获取价格

数据手册

如果您发现信息不准确，欢迎纠错

AN701 数据手册

AN701

Vishay Siliconix

Typical open loop voltage gain is 77 dB, and unity gain

bandwidth is typically 2.7 MHz. The soft-start circuit (see Pin 7

description) forces the output to within 0.7 V above ground,

and additional clamp diodes limit the positive output excursion

to within 2xV_BEabove V_{REF .}Operation at high frequency

allows high closed loop bandwidths and permits excellent

transient response to both input and output changes. Under

normal operation, a small 100 pF bypass capacitor is

recommended from N_INVto Comp to increase high-frequency

noise rejection. This should be calculated, however, in

conjunction with the loop dynamics.

oscillations may occur. These can be prevented with the use

of long soft-start times. The soft-start pin can also be used as

a non-latching shutdown pin by connecting it to –V_IN. This

approach allows a shutdown with soft re-start.

PINS 8 AND 9 - OSCILLATOR

The oscillator circuit uses external timing components R_Tand

C_T. An internal divide-by-two prevents pulses with greater than

50% duty cycle, so that core saturation can be avoided. When

the R_Tterminal is connected to V_CC, comparator C₂

disconnects the oscillator output from the SYNC terminal using

SW₁, and allows an external oscillator circuit to take control of

the current mode comparator circuit.

PIN 7: SOFTĆSTART

The soft-start circuit is designed to help dc-to-dc converters

start in an orderly manner and reduce component stress. The

output of the error amplifier is clamped by a PNP transistor.

The current programmed by R_Tdefines the charging current of

C_Tand the on and off times with the following design

equations:

The external capacitor C_SSis supplied by a 20-mA current

source and will charge linearly to 4.6 V. In the event of an

under-voltage lockout (or during start-up), this capacitor is held

low.

1.025 x R_Tx C_T

(1)

(2)

(3)

t_ON

where R = 25 W

t_OFF+ 5 x R_qlx C_T

t_ON) t_OFF

Feedback

Error Amp

f_OSC

Actual values taken from a prototype board have been

plotted (Figure 6), and are a close match (except for 47 pF,

where stray parasitics have more significant effect).

REF

Comparator

4.6 V

20 mA

1000

47 pF

100 pF

150 pF

200 pF

100

UV-low

Note: These curves were measured in

board with 3.5 pF of

Figure 5 Soft-Start

external parasitic capacitance.

Soft-start is a very important feature and has many beneficial

effects, especially in applications connecting to telecom lines

where source impedances are high. In such cases, there is an

initial start-up current caused by the input capacitor, followed

by a secondary peak caused by the converter running at

maximum duty cycle while trying to reach regulation. Where

large output capacitances and peak loads are encountered,

100

(kW)

1000

OSC

Figure 6 Oscillator Frequency Selection

Document Number: 70575

16-Jan-01

www.vishay.com

1 2 345 6 7...20

中文翻译

下载PDF

与AN701相关器件

型号	品牌	获取价格	描述	数据表
AN7017	PANASONIC	获取价格	FM/TV Front-end ICs for 1.5V Headphone Stereo, Radio Cassette Recorder
AN7017S	PANASONIC	获取价格	FM/TV Front-end ICs for 1.5V Headphone Stereo, Radio Cassette Recorder
AN7017SB	PANASONIC	获取价格	FM/TV Front-end ICs for 1.5V Headphone Stereo, Radio Cassette Recorder
AN7024	ETC	获取价格	AM/FM Receiver Circuit
AN7025K	ETC	获取价格	AM/FM Receiver Circuit
AN7030S	PANASONIC	获取价格	Audio Preamplifier, 1 Channel(s), 1 Func, Bipolar, PDSO42, 0.450 INCH, PLASTIC, SSOP-42
AN7035SC	PANASONIC	获取价格	Consumer Circuit, Bipolar, PDSO32, 0.375 INCH, PLASTIC, SSOP-32
AN7036FHP	PANASONIC	获取价格	Consumer Circuit, Bipolar, PQFP48, 7 X 7 MM, PLASTIC, QFH-48
AN7050	ETC	获取价格	Dual Audio Amplifier
AN706	PANASONIC	获取价格	High Voltage Input Amplifier Circuit for Hi-Fi Power Amplifier

与AN701相关文章

压敏电阻器在直流电路中的过压保护应用探讨
2024-06-07

1
电感耐压值及其与电感大小的关系
2024-06-07

4
CNY17F光耦合器：特性、应用、封装、引脚功能及替换型号解析
2024-06-07

3
DS1307资料解析：特性、引脚说明、替代推荐
2024-06-07

2

产品中心

服务支持

精选活动

关于我们

帮助中心

AN701

AN701 数据手册

与AN701相关器件

与AN701相关文章

您还可以找

产品中心

服务支持

精选活动

关于我们

帮助中心

AN701

AN701 数据手册

与AN701相关器件

与AN701相关文章

您还可以找

您在本页遇到什么问题？