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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： | 7/41页 |
| 文件大小： | 1002K |
| 代理商： | L5987ATR |
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L5987
Functional description
Doc ID 14972 Rev 3
15/41
5.7
Maximum DC output current L5987A (HSOP8)
The L5987A can manage DC output currents up to 3 A and the rated RMS current of its
internal power switch is 3 A. So the L5987A can deliver 3 A with 100% of duty cycle.
5.8
Maximum DC output current L5987 (VFQFPN)
The L5987 can manage DC output currents up to 3 A. However the rated RMS current of its
internal power switch is 2.5 A.
Since the current flows through the integrated power element only during the on time, the
RMS value is given by:
Equation 3
Where D is the duty cycle (VO/VIN).
Considering IO = 3 A, the maximum duty cycle that can be managed is:
Equation 4
In Figure 9 the maximum DC output current is reported as a function of the duty cycle. For
duty cycles lower than 69%, the RMS current does not limit the maximum DC output current
of 3 A. For duty cycles higher than the 69% the maximum DC output current is limited by the
RMS current to:
Equation 5
In order to have a more accurate calculation of the maximum DC output current, the
complete expression for the duty cycle can be adopted, considering the voltage drop across
the power MOSFET, the series resistance of the inductor and the forward voltage of the
rectification diode. The duty cycle results:
Equation 6
where IO is the desired DC output current.
For example with VIN = 5 V, VOUT = 3.3 V, IO = 2.6 A, RDS(on) = 220 mΩ, VF = 0.35 V and
DCR = 30 m
Ω, the duty results D = 78%, so according to Equation 5 the maximum DC
output current is 2.83 A, which is higher than desired current.
I
RMS
I
O
D
=
D
I
RMS
2
I
O
2
------------
69%
==
I
OMAX
,
2.5
D
--------
=
A
[]
if D
69%
≥
D
V
OUT
V
F
DCR I
O
++
V
IN
V
F
R
DSON
I
O
–
+
----------------------------------------------------------
=
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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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