参数资料
型号: LT3973EDD#TRPBF
厂商: Linear Technology
文件页数: 16/24页
文件大小: 0K
描述: IC REG BUCK ADJ 0.75A 10DFN
标准包装: 2,500
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:
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: 带卷 (TR)
供应商设备封装: 10-DFN(3x3)
LT3973/LT3973-3.3/LT3973-5
APPLICATIONS INFORMATION
than 1.9V above the SW pin for best efficiency. For out-
puts of 2.2V and above, the standard circuit (Figure 4a) is
best. For outputs between 2.2V and 2.5V, use a 1μF boost
capacitor. For output voltages below 2.2V, the boost diode
can be tied to the input (Figure 4b), or to another external
supply greater than 2.2V. However, the circuit in Figure 4a
is more efficient because the BOOST pin current and BD
pin quiescent current come from a lower voltage source.
You must also be sure that the maximum voltage ratings
of the BOOST and BD pins are not exceeded.
V OUT
BD
5.0
4.5
4.0
3.5
3.0
2.5
FRONT PAGE APPLICATION
V OUT = 3.3V
TO START/TO RUN
0 100 200 300 400 500 600 700
LOAD CURRENT (mA)
V IN
V IN
BOOST
LT3973
SW
C3
6.5
FRONT PAGE APPLICATION
V OUT = 5V
GND
6.0
(4a) For V OUT ≥ 2.2V
5.5
5.0
TO START/TO RUN
V IN
V IN
BD
BOOST
LT3973
C3
4.5
GND
SW
V OUT
4.0
0
100 200 300 400 500 600 700
LOAD CURRENT (mA)
3973 F05
3973 F04
(4b) For V OUT < 2.2V; V IN < 25V
Figure 4. Two Circuits for Generating the Boost Voltage
The LT3973 monitors the boost capacitor for sufficient
voltage such that the switch is allowed to fully saturate.
During start-up conditions when the boost capacitor may
not be fully charged, the switch will operate with about
1V of drop, and an internal current source will begin to
pull 70mA (typical) from the OUT pin which is typically
connected to V OUT . This current forces the LT3973 to
switch more often and with more inductor current, which
recharges the boost capacitor. When the boost capacitor
is sufficiently charged, the current source turns off, and
the part may enter Burst Mode. See Figure 5 for minimum
input voltage for outputs of 3.3V and 5V.
Figure 5. The Minimum Input Voltage Depends on
Output Voltage, Load Current and Boost Circuit
Minimum Dropout Voltage
When the OUT pin is tied to V OUT , the LT3973 regulates
the output such that:
V IN – V OUT > V DROPOUT(MIN)
where V DROPOUT(MIN) is 530mV. This enforced minimum
dropout voltage keeps the boost capacitor charged regard-
less of load during dropout conditions. The LT3973 achieves
this by limiting the duty cycle and forcing the switch to turn
off regularly to charge the boost capacitor. Since sufficient
voltage across the boost capacitor is maintained, the switch
is allowed to fully saturate and the internal switch drop
stays low for good dropout performance. Figure 6 shows
the overall V IN to V OUT performance during start-up and
dropout conditions.
3973fa
16
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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
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