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| 型号： | L6731D |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 稳压器 |
| 英文描述： | 20 A SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | HTSSOP-16 |
| 文件页数： | 9/23页 |
| 文件大小： | 386K |
| 代理商： | L6731D |
L6731D
Application details
17/23
6
Application details
6.1
Inductor design
The inductance value is defined by a compromise between the transient response time, the
efficiency, the cost and the size. The inductor has to be calculated to sustain the output and
the input voltage variation to maintain the ripple current (
I
L) between 20 % and 30 % of the
maximum output current. The inductance value can be calculated with the following
relationship:
Equation 2
Where FSW is the switching frequency, Vin is the input voltage and Vout is the output
voltage. Increasing the value of the inductance reduces the ripple current but, at the same
time, increases the converter response time to a load transient. If the compensation network
is well designed, during a load transient the device is able to set the duty cycle to 100 % or
to 0 %. When one of these conditions is reached, the response time is limited by the time
required to change the inductor current. During this time the output current is supplied by
the output capacitors. Minimizing the response time can minimize the output capacitor size.
6.2
Output capacitors
The output capacitors are basic components for the fast transient response of the power
supply. They depend on the output voltage ripple requirements, as well as any output
voltage deviation requirement during a load transient. During a load transient, the output
capacitors supply the current to the load or absorb the current stored in the inductor until the
converter reacts. In fact, even if the controller recognizes immediately the load transient and
sets the duty cycle at 100 % or 0 %, the current slope is limited by the inductor value. The
output voltage has a first drop due to the current variation inside the capacitor (neglecting
the effect of the ESL):
Equation 3
Moreover, there is an additional drop due to the effective capacitor discharge or charge that
is given by the following formulas:
Equation 4
Equation 5
Formula (4) is valid in case of positive load transient while the formula (5) is valid in case of
negative load transient. DMAX is the maximum duty cycle value that in the L6731D is 100%.
Vin
Vout
I
Fsw
Vout
Vin
L
ESR
Iout
Vout
ESR
=
)
max
min
,
(
2
Vout
D
Vin
Cout
L
Iout
Vout
COUT
=
Vout
Cout
L
Iout
Vout
COUT
=
2
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相关代理商/技术参数 |
参数描述 |
|---|---|
| L6731DTR | 功能描述:DC/DC 开关控制器 Adjustable Step Down Controller RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| L6732 | 功能描述:DC/DC 开关控制器 Adjustable Step Down Controller RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| L6732_08 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:Adjustable step-down controller with synchronous rectification |
| L6732_0906 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:Adjustable step-down controller with synchronous rectification |
| L6732C | 功能描述:DC/DC 开关控制器 Adjustable Step Down Controller RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
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