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參數(shù)資料
| 型號： | MIC2194BM |
| 廠商： | MICREL INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 400kHz SO-8 Buck Control IC |
| 中文描述： | SWITCHING CONTROLLER, 440 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | SOIC-8 |
| 文件頁數(shù)： | 8/10頁 |
| 文件大?。?/td> | 63K |
| 代理商： | MIC2194BM |
MIC2194
Micrel
MIC2194
8
October 2002
1.5V
Typical
140mV
Hysteresis
(typical)
EN/UVLO
(3)
MIC2194
V
IN
R1
R2
Bias
Circuitry
Figure 3. UVLO Circuitry
The line voltage turn on trip point is:
V
V
R
+
1
R
R
INPUT
ENABLE
THRESHOLD
_
=
×
2
2
where:
V
THRESHOLD
is the voltage level of the internal
comparator reference, typically 1.5V.
The input voltage hysteresis is equal to:
V
V
R
R
2
R
INPUT
HYST
HYST
_
=
×
+
1
2
where:
V
HYST
is the internal comparator hysteresis level,
typically 140mV.
V
INPUT_HYST
is the hysteresis at the input voltage
The MIC2194 will be disabled when the input voltage drops
back down to:
V
INPUT_OFF
=
V
INPUT_ENABLE
–
V
INPUT_HYST
=
(V
THRESHOLD
–
V
HYST
)
×
+
R
1
R
R
2
2
Either of 2 UVLO conditions will pull the soft start capacitor
low:
When the V
DD
voltage drops below its
undervoltage lockout level.
When the enable pin drops below the its enable
threshold
The internal bias circuit generates an internal 1.245V band-
gap reference voltage for the voltage error amplifier and a 3V
VDD voltage for the internal control circuitry. The VDD pin
must be decoupled with a 1
μ
F ceramic capacitor. The capaci-
tor must be placed close to the VDD pin. The other end of the
capacitor must be connected directly to the ground plane.
MOSFET Gate Drive
The MIC2194 is designed to drive a high-side P-channel
MOSFET. The source pin of the P-channel MOSFET is
connected to the input of the power supply. It is turned on
when OUTP pulls the gate of the MOSFET low. The advan-
tage of using a P-channel MOSFET is that it does not require
a bootstrap circuit to boost the gate voltage higher than the
input, as would be required for an N-channel MOSFET. The
VIN pin (pin 8) supplies the drive voltage to the gate drive pin,
OUTP.
MOSFET Selection
The P-channel MOSFET must have a V
GS
threshold voltage
equal to or lower than the input voltage when used in a buck
converter topology. There is a limit to the maximum gate
charge the MIC2194 will drive. MOSFETs with high gate
charge will have slower turn-on and turn-off times. Slower
transition times will cause higher power dissipation in the
MOSFET due to higher switching transition losses.
The MOSFET gate charge is also limited by power dissipation
in the MIC2194. The power dissipated by the gate drive
circuitry is calculated below:
P
GATE_DRIVE
= Q
GATE
×
V
IN
×
f
S
where: Q
GATE
is the total gate charge of both the N- and P-
channel MOSFETs.
f
S
is the switching frequency
V
IN
is the gate drive voltage
The graph in Figure 4 shows the total gate charge that can be
driven by the MIC2194 over the input voltage range, for
different values of switching frequency.
0
50
100
150
200
250
0
5
10
15
M
INPUT VOLTAGE (V)
Max Gate Charge
Figure 4. MIC2194 V
IN
vs Max. Gate Charge
Oscillator
The internal oscillator is free running and requires no external
components. The maximum duty cycle for both frequencies
is 100%. This is another advantage of using a P-channel
MOSFET for the high-side drive; it can be continuously turned
on.
A frequency foldback mode is enabled if the voltage on the
feedback pin (pin 2) is less than 0.3V. In frequency foldback,
the oscillator frequency is reduced by approximately a factor
of 4. Frequency foldback is used to limit the energy delivered
to the output during a short circuit fault condition.
Voltage Setting Components
The MIC2194 requires two resistors to set the output voltage
as shown in Figure 5.
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| MIC2194BM TR | 功能描述:IC REG CTRLR BST PWM CM 8-SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
| MIC2194YM | 功能描述:DC/DC 開關(guān)控制器 SO-8 3V Buck Contoller (Lead Free) RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| MIC2194YM TR | 功能描述:DC/DC 開關(guān)控制器 SO-8 3V Buck Contoller (Lead Free) RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
| MIC2196 | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:400kHz SO-8 Boost Control IC |
| MIC2196_08 | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:400kHz SO-8 Boost Control IC |
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