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| 型号： | LT3973EDD#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 17/24页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 0.75A 10DFN |
| 标准包装： | 121 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.21 V ~ 24 V |
| 输入电压： | 4.2 V ~ 42 V |
| PWM 型： | 电流模式，Burst Mode? |
| 频率 - 开关： | 195kHz ~ 2.15MHz |
| 电流 - 输出： | 750mA |
| 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： | 10-WFDFN 裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 10-DFN（3x3） |
LT3973/LT3973-3.3/LT3973-5
APPLICATIONS INFORMATION
V UVLO =
R3 + R4
Duringdropoutconditionswhentheoutputisbelowregula-
tion, the output ripple may increase. At very high loads, this
ripple can increase to approximately 200mV for the front
page application. If lower output ripple is desired during
such conditions, a larger output capacitor can be used.
In order to not exceed the maximum voltage rating, tie
the OUT pin to GND for programmed outputs greater than
14V. Note that this will result in degraded start-up and
dropout performance.
? 1.19V
R4
where switching should not start until V IN is above V UVLO .
Note that due to the comparator’s hysteresis, switching
will not stop until the input falls slightly below V UVLO .
Undervoltage lockout is functional only when V UVLO is
greater than 5.5V.
9
FRONT PAGE APPLICATION
V IN
V IN
LT3973
8
7
6
5
4
V IN
V OUT
R3
R4
1.19V
EN/UVLO
+
–
SHDN
3973 F07
3
2
1
Figure 7. Undervoltage Lockout
0
D4
BD
TIME
3973 F06
Figure 6. V IN to V OUT Performance
V IN
V IN BOOST
LT3973
EN/UVLO SW
V OUT
Enable and Undervoltage Lockout
GND
FB
+
BACKUP
The LT3973 is in shutdown when the EN/UVLO pin is low
and active when the pin is high. The rising threshold of the
EN/UVLO comparator is 1.19V, with a 30mV hysteresis.
This threshold is accurate when V IN is above 4.2V. If V IN
is lower than 4.2V, tie EN/UVLO pin to GND to place the
part in shutdown.
Figure 7 shows how to add undervoltage lockout (UVLO)
to the LT3973. Typically, UVLO is used in situations where
the input supply is current limited, or has a relatively high
source resistance. A switching regulator draws constant
power from the source, so source current increases as
source voltage drops. This looks like a negative resistance
load to the source and can cause the source to current limit
or latch low under low source voltage conditions. UVLO
prevents the regulator from operating at source voltages
where the problems might occur. The UVLO threshold can
be adjusted by setting the values R3 and R4 such that they
satisfy the following equation:
3973 F08
Figure 8. Diode D4 Prevents a Shorted Input from Discharging a
Backup Battery Tied to the Output. It Also Protects the Circuit from
a Reversed Input. The LT3973 Runs Only When the Input Is Present
Shorted and Reversed Input Protection
If the inductor is chosen so that it won’t saturate excessively,
a LT3973 buck regulator will tolerate a shorted output. There
is another situation to consider in systems where the output
will be held high when the input to the LT3973 is absent.
This may occur in battery charging applications or in battery
backup systems where a battery or some other supply is
diode ORed with the LT3973’s output. If the V IN pin is allowed
to float and the EN/UVLO pin is held high (either by a logic
signal or because it is tied to V IN ), then the LT3973’s internal
circuitry will pull its quiescent current through its SW pin.
This is fine if the system can tolerate a few μA in this state.
3973fa
17
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3973EMSE#PBF | 功能描述:IC REG BUCK ADJ 0.75A 10MSOP 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 |
| LT3973EMSE#TRPBF | 功能描述:IC REG BUCK ADJ 0.75A 10MSOP 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:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3973EMSE-3.3#PBF | 功能描述:IC REG BUCK 3.3V 0.75A 10MSOP 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 |
| LT3973EMSE-3.3#TRPBF | 功能描述:IC REG BUCK 3.3V 0.75A 10MSOP 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:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3973EMSE-5#PBF | 功能描述:IC REG BUCK 5V 0.75A 10MSOP 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 |
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