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| 型号： | MIC9131YM |
| 厂商： | Micrel Inc |
| 文件页数： | 13/19页 |
| 文件大小： | 0K |
| 描述： | IC CTRLR DC-DC PWM HV HS 16-SOIC |
| 标准包装： | 48 |
| 应用： | 控制器，电信 |
| 输入电压： | 9 V ~ 18 V |
| 输出数： | 1 |
| 输出电压： | 4.7 V ~ 5 V |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | 16-SOIC |
| 包装： | 管件 |
| 产品目录页面： | 1086 (CN2011-ZH PDF) |
| 其它名称： | 576-2419 MIC9131YM-ND |
Gate Drive
MIC9131
cycle of the gate drive output increases until the error ampli-
?er takes control of the duty cycle. The soft start capacitor is
discharged by an internal MOSFET in the MIC9131.
The soft start circuit is activated by the following events:
1. Line undervoltage pin less than the 1.21V threshold
2. V CC becomes less than the pre-regulator voltage turn
off threshold.
3. The current limit comparator threshold is exceeded.
This can be disabled with a low level on the CPWR
pin.
4. A low level on the enable pin.
Calculating the soft capacitor depends on many parameters
such as the current limit of the circuit input voltage, output
power and output loading. A starting value of capacitor should
be chosen and the value can be adjusted later in the design.
Recommended starting values of soft start capacitance is
typically 10nF to 100nF. Values below 1nF may be ineffective
in slowing the output voltage turn on time.
CPWR Current Limit Selection
This pin controls whether the soft start circuit is reset if the
voltage on the Isns pin exceeds the overcurrent threshold.
When the CPWR pin is high, an overcurrent condition at the
ISNS pin will terminate the on-time of the gate drive pulse and
discharge the soft start capacitor to 0V. This delay in start up
contributes to a reduction in the average output current during
an overcurrent or short circuit condition. A smaller MOSFET
may be used since the power dissipation in the MOSFET is
minimized under short circuit or overcurrent conditions.
If the CPWR pin is low an overcurrent or short circuit condi-
tions will not trip the soft start circuit. The pulse-by-pulse
current limit, inherent in current mode control, provides a
“brick wall” or constant current limit. With the power supply
operating in this mode, a smaller soft start capacitor can be
used to increase the turn on speed of the supply.
Micrel, Inc.
of the output is dependent on the IC supply voltage and the
gate charge required to turn the MOSFET on and off.
A resistor placed in series with the gate drive output attenu-
ates ringing in the etch connection between the MIC9131
and the MOSFET. Figure 8 shows a single resistor in series
between the driver output and the gate of the MOSFET. The
zener value should be greater than the gate drive voltage
to prevent excessive power dissipation, but less than the
maximum gate to source voltage rating.
GATE DRIVE
OUTPUT
GND
Figure 8
The circuitry shown in ?gure 9 allow different rise and fall
times. R1 and the input capacitance of the MOSFET de-
termine the rise-time of the gate voltage and therefore the
turn-on time of the MOSFET. The diode, D1 is reversed
biased, which removes R2 from the circuit. At turn-off, D1
is forward biased and the parallel combination of R1 and R2
controls the turn-off time of the MOSFET. The turn on-time
is slower, which reduces switching noise and ringing during
turn-on. The turn-off time is faster, which minimizes switching
losses during turn-off and improves ef?ciency. If the turn-on
time is to be faster than the turn-off time, the diode should
be reversed.
R2 D1
R1
Output
If the CPWR in is held low during the initial turn on at power
up and then raised high, the power supply can maximize
the turn-on time at start up and still provide a high level of
overcurrent and short circuit protection. The circuit shown
in Figure 7 performs this function.
MIC9131
GND
Figure 9
D1
C1
R1
V REF
CPWR
A gate drive transformer is used where an increase in drive
voltage, isolation and/or voltage level shifting are required.
Gate drive transformers can have multiple windings and drive
multiple MOSFETs, including MOSFETs that require a drive
signal 180°C out of phase with the ICs drive signal.
AGND
Figure 7
MOSFET Gate Drive Output
The MIC9131 has the capability to directly drive the gate of
a MOSFET. The output driver consists of a complimentary
P-channel and N-channel pair. The typical switching time
Figure 10 shows a gate drive transformer circuit. The ca-
pacitor, C1 removes DC from the drive circuit and prevents
transformer saturation. R1 provides damping to eliminate
ringing in the circuit. R1 is usually in the 5 to 20 ? range,
depending on the amount of damping necessary. D1 and
D2 form a clamp circuit, which prevents the voltage from
exceeding the V GMAX level. If the gate drive is well damped,
the diodes may be removed R2 is used to allow the trans-
former to reset properly.
August 2006
13
M9999-080206
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MIC9131YM TR | 功能描述:电流型 PWM 控制器 SO-16 High Vin Telecom DC/DC PWM Control IC (Lead Free) RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MIC9131YQS | 功能描述:电流型 PWM 控制器 SO-16 High Vin Telecom DC/DC PWM Control IC (Lead Free) RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MIC9131YQS TR | 功能描述:电流型 PWM 控制器 SO-16 High Vin Telecom DC/DC PWM Control IC (Lead Free) RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MIC913BM5 | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| MIC913BM5 TR | 功能描述:IC OPAMP 350MHZ HS LP SOT23-5 RoHS:否 类别:集成电路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 标准包装:2,500 系列:- 放大器类型:通用 电路数:1 输出类型:满摆幅 转换速率:0.11 V/µs 增益带宽积:350kHz -3db带宽:- 电流 - 输入偏压:4nA 电压 - 输入偏移:20µV 电流 - 电源:260µA 电流 - 输出 / 通道:20mA 电压 - 电源，单路/双路(±):2.7 V ~ 36 V，±1.35 V ~ 18 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 供应商设备封装:8-SO 包装:带卷 (TR) |
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