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參數(shù)資料
| 型號： | MIC2183 |
| 廠商： | Micrel Semiconductor,Inc. |
| 英文描述： | Low Voltage Synchronous Buck PWM Control IC Final Information |
| 中文描述： | 低電壓同步降壓PWM控制IC決賽信息 |
| 文件頁數(shù)： | 10/12頁 |
| 文件大?。?/td> | 98K |
| 代理商： | MIC2183 |
MIC2183
Micrel
MIC2183
10
December 10, 2001
1.5V
Typical
140mV
Hysteresis
(typical)
EN/UVLO
(7)
MIC2183
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 MIC2183 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
V
DD
voltage for the internal control circuitry. The V
DD
pin must
be decoupled with a 1
μ
F ceramic capacitor. The capacitor
must be placed close to the V
DD
pin. The other end of the
capacitor must be connected directly to the ground plane.
MOSFET Gate Drive
The MIC2183 is designed to drive a high side P-channel
MOSFET and a low side N-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 advantage of using a P-channel MOSFET
is that it does not required a bootstrap circuit to boost the gate
voltage higher than the input, as would be required for an N-
channel MOSFET.
The V
IN
P pin (pin 16) supplies the drive voltage to both gate
drive pins, OUTN and OUTP. V
IN
P pin is usually connected
to the input supply. The V
IN
P pin and CSH pin must be
connected to the same potential.
A non-overlap time is built into the MOSFET driver circuitry.
This dead-time prevents the high-side and low-side MOSFET
drivers from being on at the same time. Either an external
diode or the low-side MOSFET internal parasitic diode con-
ducts the inductor current during the dead-time.
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 MIC2183 will drive. Higher gate charge MOSFETs
will slow down the turn-on and turn-off times of the MOSFETs.
Slower transition times will cause higher power dissipation in
the MOSFETs due to higher switching transition losses. The
MOSFETs must be able to completely turn on and off within
the driver non-overlap time If both MOSFETs are conducting
at the same time, shoot-through will occur, which greatly
increases power dissipation in the MOSFETs and reduces
converter efficiency.
The MOSFET gate charge is also limited by power dissipation
in the MIC2183. The power dissipated by the gate drive
circuitry is calculated below:
P
GATE_DRIVE
=
Q
where: Qgate is the total gate charge of both the N and P-
channel MOSFETs.
f
S
is the switching frequency
V
IN
P is the gate drive voltage at the V
IN
P pin
The graph in Figure 4 shows the total gate charge that can be
driven by the MIC2183 over the input voltage range, for
different values of switching frequency.
V P
f
GATE
S
×
×
40
50
60
70
80
90
100
110
120
130
140
3
5
7
9
11
13
15
T
INPUT VOLTAGE (V)
Frequency vs.
Max. Gate Charge
200kH
600kHz
500kHz
400kHz
300kHz
Figure 4. MIC2183 Frequency vs Max. Gate Charge
Oscillator & Sync
The internal oscillator is free running and requires no external
components. The f/2 pin allows the user to select from two
switching frequencies. A low level set the oscillator frequency
to 400kHz and a high level set the oscillator frequency to
200kHz. 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 continuously turned
on.
A frequency foldback mode is enabled if the voltage on the
feedback pin (pin 6) is less than 0.3V. In frequency foldback,
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MIC2183_05 | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:Low Voltage Synchronous Buck PWM Control IC |
| MIC2183BM | 功能描述:IC REG CTRLR BUCK PWM CM 16-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(biāo)準(zhǔn)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) |
| MIC2183BM TR | 功能描述:IC REG CTRLR BUCK PWM CM 16-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(biāo)準(zhǔn)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) |
| MIC2183BQS | 功能描述:IC REG CTRLR BUCK PWM CM 16-QSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)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) |
| MIC2183BQS TR | 功能描述:IC REG CTRLR BUCK PWM CM 16-QSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)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) |
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