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参数资料
| 型号： | LTC3872ETS8#TRMPBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/22页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST PWM CM TSOT23-8 |
| 标准包装： | 1 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 650kHz |
| 电源电压： | 2.75 V ~ 9.8 V |
| 降压： | 无 |
| 升压： | 是 |
| 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： | SOT-23-8 薄型，TSOT-23-8 |
| 包装： | 标准包装 |
| 产品目录页面： | 1336 (CN2011-ZH PDF) |
| 其它名称： | LTC3872ETS8#TRMPBFDKR |
LTC3872
APPLICATIONS INFORMATION
to 30V or less, and the switch node can ring during the
turn-off of the MOSFET due to layout parasitics. Check
the switching waveforms of the MOSFET directly across
the drain and source terminals using the actual PC board
layout (not just on a lab breadboard!) for excessive ringing.
driving MOSFETs with relatively high package inductance
(DPAK and bigger) or inadequate layout. A small Schottky
diode between NGATE pin and ground can prevent nega-
tive voltage spikes. Two small Schottky diodes can inhibit
positive and negative voltage spikes (Figure 5).
During the switch on-time, the control circuit limits the
maximum voltage drop across the power MOSFET to about
270mV, 100mV and 170mV at low duty cycle with IPRG
tied to V IN , GND, or left floating respectively. The peak
inductor current is therefore limited to (270mV, 170mV and
100mV)/R DS(ON) depending on the status of the IPRG pin.
300
250
200
150
IPRG = HIGH
IPRG = FLOAT
R DS(ON) ≤ V SENSE(MAX) ?
? 1+ χ ? ? I ? ρ T
The relationship between the maximum load current, duty
cycle and the R DS(ON) of the power MOSFET is:
1– D MAX
? 2 ? O(MAX)
100
50
0
1
20
IPRG = LOW
40 60
DUTY CYCLE (%)
80
100
3872 G03
V SENSE(MAX) is the maximum voltage drop across the
power MOSFET. V SENSE(MAX) is typically 270mV, 170mV and
100mV. It is reduced with increasing duty cycle as shown
in Figure 3. The r T term accounts for the temperature co-
efficient of the R DS(ON) of the MOSFET, which is typically
0.4%/°C. Figure 4 illustrates the variation of normalized
R DS(ON) over temperature for a typical power MOSFET.
Another method of choosing which power MOSFET to
use is to check what the maximum output current is for a
given R DS(ON) , since MOSFET on-resistances are available
in discrete values.
Figure 3. Maximum SENSE Threshold Voltage vs Duty Cycle
2.0
1.5
1.0
0.5
? 1+ χ ? ? R DS(ON) ? ρ T
I O(MAX) = V SENSE(MAX) ?
? 2 ?
1–D MAX
0
– 50 0 50 100 150
JUNCTION TEMPERATURE (°C)
3872 F04
Figure 4. Normalized R DS(ON) vs Temperature
It is worth noting that the 1 – D MAX relationship between
I O(MAX) and R DS(ON) can cause boost converters with a
wide input range to experience a dramatic range of maxi-
mum input and output current. This should be taken into
consideration in applications where it is important to limit
the maximum current drawn from the input supply.
V IN
SW
LTC3872
NGATE
GND
V IN
SW
LTC3872
NGATE
GND
Voltage on the NGATE pin should be within –0.3V to
(V IN ?+?0.3V) limits. Voltage stress below –0.3V and above
V IN + 0.3V can damage internal MOSFET driver, see Func-
tional Diagram. This is especially important in case of
10
For more information www.linear.com/LTC3872
Figure 5
3872 F04
3872fc
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| LTC3872HDDB#TRMPBF | 功能描述:IC REG CTRLR BST PWM CM 8-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:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3872HDDB#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 8-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:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
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| LTC3872HTS8#TRMPBF | 功能描述:IC REG CTRLR BST PWM CM TSOT23-8 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:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3872HTS8#TRPBF | 功能描述:IC REG CTRLR BST PWM CM TSOT23-8 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:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
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