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参数资料
| 型号： | L5981 |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 稳压器 |
| 英文描述： | 1 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封装： | 3 X 3 MM, 1.08 MM HEIGHT, LEAD FREE, VFQFPN-8 |
| 文件页数： | 8/37页 |
| 文件大小： | 714K |
| 代理商： | L5981 |
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Application information
L5981
16/37
Doc ID 13004 Rev 6
5.3
Output capacitor selection
The current in the capacitor has a triangular waveform which generates a voltage ripple
across it. This ripple is due to the capacitive component (charge and discharge of the output
capacitor) and the resistive component (due to the voltage drop across its ESR). So the
output capacitor has to be selected in order to have a voltage ripple compliant with the
application requirements.
The amount of the voltage ripple can be calculated starting from the current ripple obtained
by the inductor selection.
Equation 9
Usually the resistive component of the ripple is much higher than the capacitive one, if the
output capacitor adopted is not a multi layer ceramic capacitor (MLCC) with very low ESR
value.
The output capacitor is important also for loop stability: it fixes the double LC filter pole and
the zero due to its ESR. In Chapter 5.4, it will be illustrated how to consider its effect in the
system stability.
For example with VOUT = 3.3 V, VIN = 12 V, ΔIL = 0.3 A (resulting by the inductor value), in
order to have a
ΔV
OUT = 0.01VOUT, if the multi layer capacitor are adopted, 10 μF are
needed and the ESR effect on the output voltage ripple can be neglected. In case of not
negligible ESR (electrolytic or tantalum capacitors), the capacitor is chosen taking into
account its ESR value.
So in case of 100
μF with ESR = 40 μF, the resistive component of the drop dominates and
the voltage ripple is 12 mV.
The output capacitor is also important to sustain the output voltage when a load transient
with high slew rate is required by the load. When the load transient slew rate exceeds the
system bandwidth the output capacitor provides the current to the load. So if the high slew
rate load transient is required by the application the output capacitor and system bandwidth
have to be chosen in order to sustain the load transient .
In the table below some capacitor series are listed.
Table 8.
Output capacitors
Manufacturer
Series
Cap value (
μF)
Rated voltage (V)
ESR (m
Ω)
MURATA
GRM32
22 to 100
6.3 to 25
< 5
GRM31
10 to 47
6.3 to 25
< 5
PANASONIC
ECJ
10 to 22
6.3
< 5
EEFCD
10 to 68
6.3
15 to 55
SANYO
TPA/B/C
100 to 470
4 to 16
40 to 80
TDK
C3225
22 to 100
6.3
< 5
ΔV
OUT
ESR
ΔI
MAX
ΔI
MAX
8C
OUT
f
SW
-------------------------------------
+
=
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相关代理商/技术参数 |
参数描述 |
|---|---|
| L5981_08 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:1 A step-down switching regulator |
| L5981TR | 功能描述:直流/直流开关调节器 1a Step-Down Switching Reg 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 |
| L5983 | 功能描述:直流/直流开关调节器 1.5A STEP-DOWN SWITCHING REGULATOR 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 |
| L5983_08 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:1.5 A step-down switching regulator |
| L5983TR | 功能描述:直流/直流开关调节器 1.5a Step-Down Switching Reg 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 |
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