参数资料
型号: L7980A
厂商: STMICROELECTRONICS
元件分类: 稳压器
英文描述: 3.5 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO8
封装: ROHS COMPLIANT, HSOP-8
文件页数: 29/44页
文件大小: 1247K
代理商: L7980A
L7980
Application ideas
Doc ID 15181 Rev 3
35/44
7
Application ideas
7.1
Positive buck-boost
The L7980 can implement the step up/down converter with a positive output voltage.
Figure 33. shows the schematic: one power MOSFET and one Schottky diode are added to
the standard buck topology to provide 12 V output voltage with input voltage from 4.5 V to 28
V.
Figure 33.
Positive buck-boost regulator
The relationship between input and output voltage is:
Equation 33
So the duty cycle is:
Equation 34
The output voltage isn’t limited by the maximum operating voltage of the device (28 V),
because the output voltage is sense only through the resistor divider. The external power
MOSFET maximum drain to source voltage, must be higher than output voltage; the
maximum gate to source voltage must be higher than the input voltage (in Figure 33., if VIN
is higher than 16 V, the gate must be protected through zener diode and resistor)
The current flowing through the internal power MOSFET is transferred to the load only
during the OFF time, so according to the maximum DC switch current (2.0 A), the maximum
output current for the buck boost topology can be calculated from the following equation.
V
OUT
V
IN
D
1D
-------------
=
D
V
OUT
V
OUT
V
IN
+
------------------------------
=
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L7980ATR 功能描述:直流/直流开关转换器 2 A Step-Down Reg 4.5V to 28V 250 kHz RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT
L7980TR 功能描述:直流/直流开关转换器 2A DC 4.5 V to 28 V Adj 0.6V 250 kHz RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT
L7981 功能描述:直流/直流开关调节器 3A Step-Down Reg 3A DC 4.5-28V 250Khz RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5
L7981A 制造商:STMicroelectronics 功能描述:POWER CONVERSION - Rail/Tube 制造商:STMicroelectronics 功能描述:3A Step-Down Reg 3.7A 4.5 to 28V 1MHz 制造商:ST 功能描述:3A STEP-DOWN SWITCHING REGULATOR
L7981ATR 功能描述:直流/直流开关调节器 3 A Step-Down Reg 4.5V to 28V 250 kHz RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5