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| 型号： | MIC2183YQS TR |
| 厂商： | Micrel Inc |
| 文件页数： | 10/12页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 16-QSOP |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 440kHz |
| 占空比： | 100% |
| 电源电压： | 2.9 V ~ 14 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 16-SSOP（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
| 其它名称： | MIC2183YQSTR MIC2183YQSTR-ND |
MIC2183
Micrel, Inc.
V IN
1.5V
Typical
MIC2183
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
R1
Bias
Circuitry
drivers from being on at the same time. Either an external
diode or the low-side MOSFET internal parasitic diode con-
R2
EN/UVLO
(7)
140mV
Hysteresis
(typical)
ducts the inductor current during the dead-time.
MOSFET Selection
Figure 3. UVLO Circuitry
The line voltage turn on trip point is:
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
V INPUT _ ENABLE = V THRESHOLD ×
R 2
R 1 + R 2
will slow down the turn-on and turn-off times of the MOSFETs.
Slower transition times will cause higher power dissipation in
where:
V THRESHOLD is the voltage level of the internal
comparator reference, typically 1.5V
The input voltage hysteresis is equal to:
R1 + R 2
V INPUT _ HYST = V HYST ×
R 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 =
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 GATE × V IN P × f S
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
(V THRESHOLD – V HYST ) ×
R 2
R 1 + R 2
driven by the MIC2183 over the input voltage range, for
different values of switching frequency.
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
140
130
120
110
100
90
Frequency vs.
Max. Gate Charge
200kH
300kHz
The internal bias circuit generates an internal 1.245V band-
80
70
500kHz
400kHz
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
60
50
600kHz
40
3 5 7 9 11 13 15
INPUT VOLTAGE (V)
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,
M9999-042205
10
April 2005
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| MIC2184 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:Low Voltage Buck PWM Control IC Final Information |
| MIC2184_05 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:Low Voltage Buck PWM Control IC |
| MIC2184BM | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,000 系列:- PWM 型:电压模式 输出数:1 频率 - 最大:1.5MHz 占空比:66.7% 电源电压:4.75 V ~ 5.25 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 85°C 封装/外壳:40-VFQFN 裸露焊盘 包装:带卷 (TR) |
| MIC2184BM TR | 功能描述:IC REG CTRLR BUCK PWM CM 16-SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,000 系列:- PWM 型:电压模式 输出数:1 频率 - 最大:1.5MHz 占空比:66.7% 电源电压:4.75 V ~ 5.25 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 85°C 封装/外壳:40-VFQFN 裸露焊盘 包装:带卷 (TR) |
| MIC2184BQS | 功能描述:IC REG CTRLR BUCK PWM CM 16-QSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,000 系列:- PWM 型:电压模式 输出数:1 频率 - 最大:1.5MHz 占空比:66.7% 电源电压:4.75 V ~ 5.25 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 85°C 封装/外壳:40-VFQFN 裸露焊盘 包装:带卷 (TR) |
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