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| 型号： | ISL8105AIRZ-T |
| 厂商： | Intersil |
| 文件页数： | 8/16页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM VM 10-DFN |
| 标准包装： | 6,000 |
| PWM 型： | 电压模式 |
| 输出数： | 1 |
| 频率 - 最大： | 660kHz |
| 占空比： | 100% |
| 电源电压： | 6.5 V ~ 14.4 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： | 10-VFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
ISL8105, ISL8105A
MOSFETs is typically in the 20mV to 120mV ballpark
(500 Ω to 3000 Ω ). If the voltage drop across R BSOC is set
too low, that can cause almost continuous OCP tripping and
BGATE > 425ns
BGATE = 425ns
BGATE < 425ns
BGATE << 425ns
FIGURE 4. BGATE PULSE STRETCHING
The overcurrent function will trip at a peak inductor current
(I PEAK ) determined by Equation 1:
retry. It would also be very sensitive to system noise and
inrush current spikes, so it should be avoided. The maximum
usable setting is around 0.2V across R BSOC (0.4V across
the MOSFET); values above that might disable the
protection. Any voltage drop across R BSOC that is greater
than 0.3V (0.6V MOSFET trip point) will disable the OCP.
The preferred method to disable OCP is simply to remove
the resistor, which will be detected as no OCP.
Note that conditions during power-up or during a retry may
look different than normal operation. During power-up in a
12V system, the IC starts operation just above 4V; if the
supply ramp is slow, the soft-start ramp might be over well
before 12V is reached. So with bottom-side gate drive
voltages, the r DS(ON) of the MOSFETs will be higher during
power-up, effectively lowering the OCP trip. In addition, the
ripple current will likely be different at lower input voltage.
Another factor is the digital nature of the soft-start ramp. On
each discrete voltage step, there is in effect a small load
transient, and a current spike to charge the output
capacitors. The height of the current spike is not controlled; it
is affected by the step size of the output, the value of the
output capacitors, as well as the IC error amp compensation.
So it is possible to trip the overcurrent with inrush current, in
addition to the normal load and ripple considerations.
Figure 5 shows the output response during a retry of an
output shorted to GND. At time t 0 , the output has been
turned off, due to sensing an overcurrent condition. There
are two internal soft-start delay cycles (t 1 and t 2 ) to allow the
MOSFETs to cool down, to keep the average power
I PEAK = ------------------------------------------------------
2 × I BSOC × R BSOC
r DS ( ON )
(EQ. 1)
dissipation in retry at an acceptable level. At time t 2 , the
output starts a normal soft-start cycle, and the output tries to
ramp. If the short is still applied, and the current reaches the
3. Determine I PEAK for I PEAK > I OUT(MAX) + ---------- , where
Δ I is the output inductor ripple current.
where I BSOC is the internal BSOC current source (21.5μA
typical). The scale factor of 2 doubles the trip point of the
MOSFET voltage drop, compared to the setting on the
R BSOC resistor. The OC trip point varies in a system mainly
due to the MOSFET's r DS(ON) variations (over process,
current and temperature). To avoid overcurrent tripping in
the normal operating load range, find the R BSOC resistor
from Equation 1 with:
1. The maximum r DS(ON) at the highest junction
temperature
2. The minimum I BSOC from the specification table
( Δ I )
2
For an equation for the ripple current, see “Output Inductor
Selection” on page 13 .
The range of allowable voltages detected (2*I BSOC *R BSOC )
is 0mV to 475mV; but the practical range for typical
8
BSOC trip point any time during soft-start ramp period, the
output will shut off and return to time t 0 for another delay
cycle. Thus, the retry period is two dummy soft-start cycles
plus one variable one (which depends on how long it takes to
trip the sensor each time). Figure 5 also shows an example
where the output gets about half-way up before shutting
down; therefore, the retry (or hiccup) time will be around
17ms. The minimum should be nominally 13.6ms and the
maximum 20.4ms. If the short condition is finally removed,
the output should ramp up normally on the next t 2 cycle.
Starting up into a shorted load looks the same as a retry into
that same shorted load. In both cases, OCP is always
enabled during soft-start; once it trips, it will go into retry
(hiccup) mode. The retry cycle will always have two dummy
time-outs, plus whatever fraction of the real soft-start time
passes before the detection and shutoff; at that point, the
logic immediately starts a new two dummy cycle time-out.
FN6306.5
April 15, 2010
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相关代理商/技术参数 |
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| ISL8105B | 制造商:INTERSIL 制造商全称:Intersil Corporation 功能描述:+5V or +12V Single-Phase Synchronous Buck Converter PWM Controller with Integrated MOSFET Gate Drivers, Extended Soft-Start Time |
| ISL8105BCBZ | 功能描述:IC REG CTRLR BUCK PWM VM 8-SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:275kHz 占空比:50% 电源电压:18 V ~ 110 V 降压:无 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:是 工作温度:-40°C ~ 85°C 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) |
| ISL8105BCBZ-T | 功能描述:IC REG CTRLR BUCK PWM VM 8-SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| ISL8105BCRZ | 功能描述:IC REG CTRLR BUCK PWM VM 10-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:275kHz 占空比:50% 电源电压:18 V ~ 110 V 降压:无 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:是 工作温度:-40°C ~ 85°C 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) |
| ISL8105BCRZ-T | 功能描述:IC REG CTRLR BUCK PWM VM 10-DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
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