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LM5005MHX

LM5005MHX首页预览图
型号: LM5005MHX
PDF文件:
  • LM5005MHX PDF文件
  • LM5005MHX PDF在线浏览
功能描述: LM5005 High Voltage 2.5 Amp Buck Regulator
PDF文件大小: 947.25 Kbytes
PDF页数: 共28页
制造商: TI[Texas Instruments]
制造商LOGO: TI[Texas Instruments] LOGO
制造商网址: http://www.ti.com
捡单宝LM5005MHX
PDF页面索引
120%
SYNC
10k
S
R
Q
Q
DEADTIME
ONE-SHOT
5V
2.5V
I = f(RT)
LM5005
www.ti.com
SNVS397D SEPTEMBER 2005REVISED MARCH 2013
Figure 13. 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 9. This network creates a pole at unity frequency, 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 significant 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 LM5005 utilizes a unique ramp generator, which does not actually measure the buck switch
current but rather reconstructs the signal. Reconstructing or emulating the inductor current provides a ramp
signal to the PWM comparator that is free of leading edge spike and measurement or filtering delays. The current
reconstruction is comprised of two elements; a sample & hold DC level and an emulated current ramp.
Copyright © 2005–2013, Texas Instruments Incorporated Submit Documentation Feedback 11
Product Folder Links: LM5005
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