參數(shù)資料
型號： MIC2172BN
廠商： MICREL INC
元件分類： 穩(wěn)壓器
英文描述： RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS
中文描述： 3.5 A SWITCHING REGULATOR, 115 kHz SWITCHING FREQ-MAX, PDIP8
封裝： PLASTIC, DIP-8
文件頁數(shù)： 6/20頁
文件大?。?/td> 906K
代理商： MIC2172BN
Micrel
MIC2172/3172
April 2006
14
M9999-041806
(408) 955-1690
Figure 10. Single Point Ground
A single point ground is strongly recommended for
proper operation.
The signal ground, compensation network ground, and
feedback network connections are sensitive to minor
voltage variations. The input and output capacitor
grounds and power ground conductors will exhibit
voltage drop when carrying large currents. Keep the
sensitive circuit ground traces separate from the power
ground traces. Small voltage variations applied to the
sensitive circuits can prevent the MIC2172/3172 or any
switching regulator from functioning properly.
Applications and Design Hints
Access to both the collector and emitter(s) of the NPN
power switch makes the MIC2172/3172 extremely
versatile and suitable for use in most PWM power supply
topologies.
Boost Conversion
Refer to figure 11 for a typical boost conversion
application where a +5V logic supply is available but
+12V at 0.14A is required.
Figure 11. 5V to 12V Boost Converter
The first step in designing a boost converter is
determining whether inductor L1 will cause the converter
to operate in either continuous or discontinuous mode.
Discontinuous mode is preferred because the feedback
control of the converter is simpler.
When L1 discharges its current completely during the
MIC2172/3172’s off-time, it is operating in discontinuous
mode.
L1 is operating in continuous mode if it does not
discharge completely before the MIC2172/3172 power
switch is turned on again.
Discontinuous Mode Design
Given the maximum output current, solve equation (1) to
determine
whether
the
device
can
operate
in
discontinuous mode without initiating the internal device
current limit.
OUT
IN
CL
OUT
V
δ
V
2
I
≤
(1)
F
OUT
IN
F
OUT
V
δ
+
±
+
=
(1a)
Where:
ICL = internal switch current limit
ICL = 1.25A when δ < 50%
ICL = 0.833 (2 – δ) when δ ≥ 50%
(Refer to Electrical Characteristics.)
IOUT = maximum output current
VIN = minimum input voltage
δ = duty cycle
VOUT = required output voltage
VF = D1 forward voltage drop
For the example in figure 11.
IOUT = 0.14A
ICL = 1.147A
VIN = 4.75V (minimum)
δ = 0.623
VOUT = 12.0V
VF = 0.6V
Then:
0.141A
I
12
0.623
4.75
2
1.147
I
OUT
≤
×
≤
This value is greater than the 0.14A output current
requirement so we can proceed to find the inductance
value of L1.
()
SW
OUT
2
IN
f
P
2
δ
V
L1
≤
(2)
Where:
POUT = 12
0.14 = 1.68W
fSW = 1
10
5kHz (100kHz)
For our practical example:
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MIC2172YM 功能描述:直流/直流開關(guān)調(diào)節(jié)器 1.25A 100kHz Switching Regulator (Lead Free) 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: 安裝風格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5
MIC2172YM TR 功能描述:直流/直流開關(guān)調(diào)節(jié)器 1.25A 100kHz Switching Regulator (Lead Free) 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: 安裝風格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5
MIC2172YMTR 制造商:Micrel 功能描述:Current Mode PWM Controller 65V 1.25A
MIC2172YM-TR 制造商:Micrel Inc 功能描述:
MIC2172YN 功能描述:直流/直流開關(guān)調(diào)節(jié)器 2.5A 100kHz Switching Regulator (Lead Free) 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: 安裝風格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5
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