参数资料
型号: LM3423MHBSTEVAL/NOPB
厂商: National Semiconductor
文件页数: 18/67页
文件大小: 0K
描述: BOARD EVAL BOOST FOR LM3423
标准包装: 1
系列: PowerWise®
电流 - 输出 / 通道: 1A
输出及类型: 1,非隔离
输出电压: 35V
特点: 可调光
输入电压: 4.5 ~ 35 V
已供物品:
已用 IC / 零件: LM3423
其它名称: LM3423MHBSTEVAL
SNVS574E – JULY 2008 – REVISED MAY 2013
Z P 2 =
1
5 e 6 : x C CMP
(19)
It may also be necessary to add one final pole at least one decade above the crossover frequency to attenuate
switching noise and, in some cases, provide better gain margin. This pole can be placed across R SNS to filter the
ESL of the sense resistor at the same time. Figure 23 shows how the compensation is physically implemented in
the system.
The high frequency pole ( ω P3 ) can be calculated:
Z P 3 =
1
R FS x C FS
(20)
The total system transfer function becomes:
¨ 1 +
¨ 1 - s ?
Z Z 1 ? 1
? x ¨ 1 +
? x ¨ 1 +
Z P 1 ? Z P 2 ?
s ·
Z P 3 ?
T = T U 0 x
§
¨
?
s · § s · §
1 ? 1 ?
§ ·
¨
?
¨ ¨
?
1
(21)
The resulting compensated loop gain frequency response shown in Figure 24 indicates that the system has
adequate phase margin (above 45°) if the dominant compensation pole is placed low enough, ensuring stability:
80
60
? P2
90
45
40
GAIN
0
20
0
-20
-40
-60
-80
PHASE
60° Phase Margin
? Z1
? P1
? P3
-45
-90
-135
-180
-225
-270
1e-1
1e1
1e3
1e5
1e7
FREQUENCY (Hz)
Figure 24. Compensated Loop Gain Frequency Response
V CMP
0.9V
0
t VCC
t CMP
t CO
t
Figure 25. Start-Up Waveforms
18
Copyright ? 2008–2013, Texas Instruments Incorporated
Product Folder Links: LM3421 LM3421-Q1 LM3423 LM3423-Q1
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