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| 型号： | LT3581IMSE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/36页 |
| 文件大小： | 0K |
| 描述： | IC REG MULTI CONFIG ADJ 16MSOP |
| 标准包装： | 2,500 |
| 类型： | 升压（升压），反相，回扫，Sepic |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.22 V ~ 42 V |
| 输入电压： | 2.5 V ~ 22 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 200kHz ~ 2.5MHz |
| 电流 - 输出： | 3.3A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-TFSOP（0.118"，3.00mm 宽）裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 16-MSOP，裸露焊盘 |
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LT3581
OPERATION
+
OPERATION – OVERVIEW
The LT3581 uses a constant-frequency, current mode con-
trol scheme to provide excellent line and load regulation.
The part’s undervoltage lockout (UVLO) function, together
with soft-start and frequency foldback, offers a controlled
means of starting up. Fault features are incorporated in the
LT3581 to aid in the detection of output shorts, over-volt-
age, and overtemperature conditions. Refer to the Block
Diagram (Figure 1) and the State Diagram (Figure 2) for
the following description of the part’s operation.
V IN
R UVLO1
R UVLO2
(OPTIONAL)
V IN
1.33V –
SHDN
11.6μA
AT 1.33V
GND
Figure 3. Configurable UVLO
ACTIVE/
LOCKOUT
3581 F03
R UVLO 1 =
? ? + 11 . 6 μ A
OPERATION – START-UP
Several functions are provided to enable a very clean
start-up for the LT3581:
Precise Turn-On Voltage
The SHDN pin is compared to an internal voltage reference
to give a precise turn on voltage level. Taking the SHDN pin
above 1.33V (typical) enables the part. Taking the SHDN pin
below 300mV shuts down the chip, resulting in extremely
low quiescent current. The SHDN pin has 30mV of hysteresis
to protect against glitches and slow ramping.
Undervoltage Lockout (UVLO)
The SHDN pin can also be used to create a configurable
UVLO. The UVLO function sets the turn on/off of the LT3581
at a desired input voltage (V INUVLO ). Figure 3 shows how a
resistor divider (or single resistor) from V IN to the SHDN
pin can be used to set V INUVLO . R UVLO2 is optional. It may
be left out, in which case set it to infinite in the equation
below. For increased accuracy, set R UVLO2 ≤ 10k. Pick
R UVLO1 as follows:
V INUVLO – 1 . 33 V
? 1 . 33 V ?
?
? R UVLO 2
The LT3581 also has internal UVLO circuitry that disables
the chip when V IN < 2.3V (typical).
Soft-Start of Switch Current
The soft-start circuitry provides for a gradual ramp-up
of the switch current (refer to Commanded Current Limit
vs SS Voltage in Typical Performance Characteristics).
When the part is brought out of shutdown, the external
SS capacitor is first discharged which resets the states
of the logic circuits in the chip. Then an integrated 250k
resistor pulls the SS pin to ~1.8V. The ramp rate of the SS
pin voltage is set by this 250k resistor and the external
capacitor connected to this pin. Once SS gets to 1.8V, the
CLKOUT pin is enabled, and an internal regulator pulls
the pin up quickly to ~2.1V. Typical values for the external
soft-start capacitor range from 100nF to 1μF.
Soft-Start of External PMOS (if used)
The soft-start circuitry also gradually ramps up the GATE
pin pull-down current which allows an external PMOS to
slowly turn on (M1 in Block Diagram). The GATE pin current
increases linearly with the SS voltage, with a maximum
current of 933μA when the SS voltage gets above 500mV.
Note that if the GATE pin voltage is less than 2V for SS
voltages exceeding 500mV, then the GATE pin impedance
to ground is 2kΩ. The soft turn on of the external PMOS
helps limit inrush current at start-up, making hot-plugs
of LT3581s feasible and safe.
3581fa
10
For more information www.linear.com/LT3581
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| LT3582EUD#PBF | 功能描述:IC REG BOOST INV ADJ DL 16QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
| LT3582EUD#TRPBF | 功能描述:IC REG BOOST INV ADJ DL 16QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:升压（升压） 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式，混合 频率 - 开关:600kHz 电流 - 输出:500mA 同步整流器:无 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） 包装:带卷 (TR) 供应商设备封装:8-SOIC |
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