LM25575Q0MH【PDF 3/22 页】SWITCHING REGULATOR, PDSO16

收藏本站

您好，
买卖IC网欢迎您。
请登录
免费注册

买卖IC网

Sheet目录39246

1页 2页 [3页]4页 5页 6页 7页

30071107

FIGURE 5. Simplified Oscillator Block Diagram and SYNC I/O Circuit

Error Amplifier and PWM

Comparator

The internal high gain error amplifier generates an error signal

proportional to the difference between the regulated output

voltage and an internal precision reference (1.225V). The

output of the error amplifier is connected to the COMP pin

allowing the user to provide loop compensation components,

generally a type II network, as illustrated in Figure 1. This

network creates a pole at DC, a zero and a noise reducing

high frequency pole. The PWM comparator compares the

emulated current sense signal from the RAMP generator to

the error amplifier output voltage at the COMP pin.

RAMP Generator

The ramp signal used in the pulse width modulator for current

mode control is typically derived directly from the buck switch

current. This switch current corresponds to the positive slope

portion of the output inductor current. Using this signal for the

PWM ramp simplifies the control loop transfer function to a

single pole response and provides inherent input voltage

feed-forward compensation. The disadvantage of using the

buck switch current signal for PWM control is the large leading

edge spike due to circuit parasitics that must be filtered or

blanked. Also, the current measurement may introduce sig-

nificant propagation delays. The filtering, blanking time and

propagation delay limit the minimum achievable pulsewidth.

In applications where the input voltage may be relatively large

in comparison to the output voltage, controlling small

pulsewidths and duty cycles is necessary for regulation. The

LM25575Q0 utilizes a unique ramp generator, which does not

actually measure the buck switch current but rather recon-

structs the signal. Reconstructing or emulating the inductor

current provides a ramp signal to the PWM comparator that

is free of leading edge spikes and measurement or filtering

delays. The current reconstruction is comprised of two ele-

ments; a sample & hold DC level and an emulated current

ramp.

www.national.com

LM25575Q0

发布紧急采购，3分钟左右您将得到回复。

采购需求

(若只采购一条型号，填写一行即可)

*型号	*数量	厂商	批号	封装

添加更多采购

采购需求

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

我的联系方式