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參數(shù)資料
| 型號： | MIC4690 |
| 廠商： | Micrel Semiconductor,Inc. |
| 元件分類： | FPGA |
| 英文描述： | 150000 SYSTEM GATE 2.5 VOLT FPGA - NOT RECOMMENDED for NEW DESIGN |
| 中文描述： | 500kHz的第1A SuperSwitcher降壓穩(wěn)壓器 |
| 文件頁數(shù)： | 7/12頁 |
| 文件大小： | 225K |
| 代理商： | MIC4690 |
June 2001
7
MIC4690
MIC4690
Block Diagrams
Micrel
SW
FB
R1
R2
C
OUT
V
IN
IN
V
OUT
MIC4690 [adj.]
Internal
Regulator
SHDN
500kHz
Oscillator
Thermal
Shutdown
Reset
Current
Limit
Com-
parator
Error
Amp
Driver
1.23V
Bandgap
Reference
V
V
R1
R2
1
R1 R2
V
V
1
V
1.23V
OUT
REF
OUT
REF
REF
=
+
=
Adjustable Regulator
Functional Description
The MIC4690 is a variable duty cycle switch-mode regulator
with an internal power switch. Refer to the block diagrams.
Supply Voltage
The MIC4690 operates from a +4V to +30V (transients to
34V) unregulated input. Highest efficiency operation is from
a supply voltage around +12V. See the efficiency curve on
page 5.
Enable/Shutdown
The shutdown (
SHDN
) input is TTL compatible. A logic-low
enables the regulator. A logic-high shuts down the internal
regulator which reduces the current to typically 1.5
μ
A when
V
SHDN
= V
IN
= 12V and 30
μ
A when V
SHDN
= 5V. See
“
Shutdown Input Behavior: Shutdown Hysteresis.
”
Feedback
Fixed-voltage versions of the regulator have an internal
resistive divider from the feedback (
FB
) pin. Connect
FB
directly to the output voltage.
Adjustable versions require an external resistive voltage
divider from the output voltage to ground, center tapped to the
FB
pin. See Figure 1b for recommended resistor values.
Duty Cycle Control
A fixed-gain error amplifier compares the feedback signal
with a 1.23V bandgap voltage reference. The resulting error
amplifier output voltage is compared to a 500kHz sawtooth
waveform to produce a voltage controlled variable duty cycle
output.
A higher feedback voltage increases the error amplifier
output voltage. A higher error amplifier voltage (comparator
inverting input) causes the comparator to detect only the
peaks of the sawtooth, reducing the duty cycle of the com-
parator output. A lower feedback voltage increases the duty
cycle. The MIC4690 uses a voltage-mode control architec-
ture.
Output Switching
When the internal switch is ON, an increasing current flows
from the supply V
IN,
through external storage inductor L1, to
output capacitor C
OUT
and the load. Energy is stored in the
inductor as the current increases with time.
When the internal switch is turned OFF, the collapse of the
magnetic field in L1 forces current to flow through fast
recovery diode D1, charging C
OUT
.
Output Capacitor
External output capacitor C
OUT
provides stabilization and
reduces ripple.
Return Paths
During the ON portion of the cycle, the output capacitor and
load currents return to the supply ground. During the OFF
portion of the cycle, current is being supplied to the output
capacitor and load by storage inductor L1, which means that
D1 is part of the high-current return path.
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| MIC4690_05 | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:500kHz 1A SuperSwitcher Buck Regulator |
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| MIC4690BM TR | 功能描述:IC REG BUCK ADJ 1A 8SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:SuperSwitcher™ 標準包裝:20 系列:SIMPLE SWITCHER® 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:12V 輸入電壓:4 V ~ 60 V PWM 型:電壓模式 頻率 - 開關(guān):52kHz 電流 - 輸出:1A 同步整流器:無 工作溫度:-40°C ~ 125°C 安裝類型:通孔 封裝/外殼:16-DIP（0.300"，7.62mm） 包裝:管件 供應(yīng)商設(shè)備封裝:16-DIP 其它名稱:*LM2575HVN-12LM2575HVN-12 |
| MIC4690YM | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 SO-8 500KHz Simple Buck 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 |
| MIC4690YM TR | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 SO-8 500KHz Simple Buck 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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