參數(shù)資料
型號(hào)： LM25005MH
廠商： NATIONAL SEMICONDUCTOR CORP
元件分類： 穩(wěn)壓器
英文描述： 42V, 2.5A STEP-DOWN SWITCHING REGULATOR
中文描述： 4.25 A SWITCHING REGULATOR, 525 kHz SWITCHING FREQ-MAX, PDSO20
封裝： TSSOP-20
文件頁(yè)數(shù)： 13/21頁(yè)
文件大小： 756K
代理商： LM25005MH
RAMP Generator
(Continued)
The Sample and Hold DC level illustrated in Figure 6. is
derived from a measurement of the re-circulating Schottky
diode anode current. The re-circulating diode anode should
be connected to the IS pin. The diode current flows through
an internal current sense resistor between the IS and PGND
pins. The voltage level across the sense resistor is sampled
and held just prior to the onset of the next conduction interval
of the buck switch. The diode current sensing and sample &
hold provide the dc level of the reconstructed current signal.
The positive slope inductor current ramp is emulated by an
external capacitor connected from the RAMP pin to AGND
and an internal voltage controlled current source. The ramp
current source that emulates the inductor current is a func-
tion of the Vin and Vout voltages per the following equation:
I
RAMP
= (5μ x (Vin – Vout)) + 25μA
Proper selection of the RAMP capacitor depends upon the
selected value of the output inductor. The value of C
RAMP
can be selected from: C
RAMP
= L x 10
-5
, where L is the value
of the output inductor in Henrys. With this value, the scale
factor of the emulated current ramp will be approximately
equal to the scale factor of the dc level sample and hold ( 0.5
V / A). The C
RAMP
capacitor should be located very close to
the device and connected directly to the pins of the IC
(RAMP and AGND).
For duty cycles greater than 50 percent, current mode con-
trol circuits are subject to sub-harmonic oscillation. Adding a
fixed slope voltage ramp signal (slope compensation) to the
current sense signal prevents this oscillation. The 25μA of
offset current provided from the emulated current source
adds some fixed slope to the ramp signal. In some very high
duty cycle applications, additional slope may be required. In
these applications, the ramp capacitor value can be de-
creased to increase the ramp slope compensation.
20170008
FIGURE 6. Composition of Current Sense Signal
L
www.national.com
13
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LM25005MH/NOPB 功能描述:直流/直流開關(guān)調(diào)節(jié)器 42V,2.5A STEP-DOWN SWITCHING REG RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5
LM25005MHX 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
LM25005MHX/NOPB 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
LM25007 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Boot Capacitor Regulation in LM25007 Constant-On-Time (COT) Converter
LM25007_08 制造商:NSC 制造商全稱:National Semiconductor 功能描述:42V, 0.5A Step-Down Switching Regulator
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