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参数资料
| 型号： | L5987ATR |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 稳压器 |
| 英文描述： | 4.4 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封装： | ROHS COMPLIANT, HSOP-8 |
| 文件页数： | 10/41页 |
| 文件大小： | 1002K |
| 代理商： | L5987ATR |
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Application information
L5987
18/41
Doc ID 14972 Rev 3
6.2
Inductor selection
The inductance value fixes the current ripple flowing through the output capacitor. So the
minimum inductance value in order to have the expected current ripple has to be selected.
The rule to fix the current ripple value is to have a ripple at 20%-40% of the output current.
In the continuos current mode (CCM), the inductance value can be calculated by the
following equation:
Equation 10
Where TON is the conduction time of the internal high side switch and TOFF is the conduction
time of the external diode (in CCM, FSW = 1/(TON + TOFF)). The maximum current ripple, at
fixed Vout, is obtained at maximum TOFF that is at minimum duty cycle (see previous section
to calculate minimum duty). So fixing
ΔI
L = 20% to 30% of the maximum output current, the
minimum inductance value can be calculated:
Equation 11
where FSW is the switching frequency, 1/(TON + TOFF).
For example for VOUT = 3.3 V, VIN = 12 V, IO = 3 A and FSW = 250 kHz the minimum
inductance value to have
ΔI
L = 30% of IO is about 10 μH.
The peak current through the inductor is given by:
Equation 12
So if the inductor value decreases, the peak current (that has to be lower than the current
limit of the device) increases. The higher is the inductor value, the higher is the average
output current that can be delivered, without reaching the current limit.
In the table below some inductor part numbers are listed.
Table 7.
Inductors
Manufacturer
Series
Inductor value (
μH)
Saturation current (A)
Coilcraft
MSS1038
3.8 to 10
3.9 to 6.5
MSS1048
12 to 22
3.84 to 5.34
Wurth
PD Type L
8.2 to 15
3.75 to 6.25
PD Type M
2.2 to 4.7
4 to 6
SUMIDA
CDRH6D226/HP
1.5 to 3.3
3.6 to 5.2
CDR10D48MN
6.6 to 12
4.1 to 5.7
ΔI
L
V
IN
V
OUT
–
L
------------------------------ T
ON
V
OUT
V
F
+
L
---------------------------- T
OFF
==
L
MIN
V
OUT
V
F
+
ΔI
MAX
----------------------------
1D
MIN
–
F
SW
-----------------------
=
I
LPK
,
I
O
ΔI
L
2
--------
+
=
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相关代理商/技术参数 |
参数描述 |
|---|---|
| L5987TR | 功能描述:直流/直流开关调节器 3 A Step-down Switch 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 |
| L5988 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:4A step-down switching regulator with synchronous rectification |
| L5988D | 功能描述:直流/直流开关调节器 STEP DOWN SWITCH 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 |
| L5988DTR | 功能描述:直流/直流开关调节器 4A Step Down Reg 2.9V to 18V 200ns 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 |
| L5989D | 功能描述:直流/直流开关调节器 4A cont 5A pulsed step-down sw 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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