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参数资料
| 型号： | LT3970HMS-3.3#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 13/22页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 3.3V 0.35A 10MSOP |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 3.3V |
| 输入电压： | 4.2 V ~ 40 V |
| PWM 型： | 电流模式，Burst Mode? |
| 频率 - 开关： | 200kHz ~ 2.25MHz |
| 电流 - 输出： | 350mA |
| 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-TFSOP，10-MSOP（0.118"，3.00mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 10-MSOP |
LT3970 Series
APPLICATIONS INFORMATION
operation, the noise is typically very quiet to a casual ear.
If this is unacceptable, use a high performance tantalum
or electrolytic capacitor at the output.
700
600
FRONT PAGE APPLICATION
A final precaution regarding ceramic capacitors concerns
the maximum input voltage rating of the LT3970. As pre-
viously mentioned, a ceramic input capacitor combined
with trace or cable inductance forms a high quality (under
damped) tank circuit. If the LT3970 circuit is plugged into a
live supply, the input voltage can ring to twice its nominal
value, possibly exceeding the LT3970’s rating. This situation
is easily avoided (see the Hot Plugging Safely section).
500
400
300
200
100
0
0
50
100 150 200 250
LOAD CURRENT (mA)
300
350
2μs/DIV
13
Low Ripple Burst Mode Operation
To enhance efficiency at light loads, the LT3970 operates
in low ripple Burst Mode operation which keeps the output
capacitor charged to the proper voltage while minimizing
the input quiescent current. During Burst Mode opera-
tion, the LT3970 delivers single cycle bursts of current to
the output capacitor followed by sleep periods where the
output power is delivered to the load by the output capaci-
tor. Because the LT3970 delivers power to the output with
single, low current pulses, the output ripple is kept below
5mV for a typical application. See Figure 2.
As the load current decreases towards a no load condition,
the percentage of time that the LT3970 operates in sleep
mode increases and the average input current is greatly
reduced resulting in high efficiency even at very low loads.
Note that during Burst Mode operation, the switching
frequency will be lower than the programmed switching
frequency. See Figure 3.
V SW
5V/DIV
I L
100mA/DIV
V OUT
5mV/DIV
3970 F02
FRONT PAGE APPLICATION
V IN = 12V
V OUT = 5V
I LOAD = 10mA
Figure 2. Burst Mode Operation
3070 F03
Figure 3. Switching Frequency in Burst Mode Operation
At higher output loads (above ~45mA for the front page
application) the LT3970 will be running at the frequency
programmed by the R T resistor, and will be operating in
standard PWM mode. The transition between PWM and
low ripple Burst Mode is seamless, and will not disturb
the output voltage.
BOOST and BD Pin Considerations
Capacitor C3 and the internal boost Schottky diode (see the
Block Diagram) are used to generate a boost voltage that
is higher than the input voltage. In most cases a 0.22μF
capacitor will work well. Figure 4 shows two ways to ar-
range the boost circuit. The BOOST pin must be more than
1.9V above the SW pin for best efficiency. For outputs of
2.2V and above, the standard circuit (Figure 4a) is best.
For outputs between 2.2V and 2.5V, use a 0.47μF 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.
Also, be sure that the maximum voltage ratings of the
BOOST and BD pins are not exceeded.
The minimum operating voltage of an LT3970 application
is limited by the minimum input voltage (4.2V) and by the
maximum duty cycle as outlined in a previous section. For
output voltages greater than 3.4V, the minimum input volt-
age is also limited by the boost circuit for proper start-up.
3970fc
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| LT3970HMS-5#PBF | 功能描述:IC REG BUCK 5V 0.35A 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 |
| LT3970HMS-5#TRPBF | 功能描述:IC REG BUCK 5V 0.35A 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 |
| LT3970HMS-5-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:40V, 350mA Step-Down Regulator with 2.5μA Quiescent Current and Integrated Diodes |
| LT3970HMS-5-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:40V, 350mA Step-Down Regulator with 2.5μA Quiescent Current and Integrated Diodes |
| LT3970IDDB#PBF | 制造商:Linear Technology 功能描述:Conv DC-DC Single Step Down 4.2V to 40V 10-Pin DFN EP 制造商:Linear Technology 功能描述:Bulk |
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