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| 型号： | LMZ10504EXTTZX |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 6.7 A SWITCHING REGULATOR, 1160 kHz SWITCHING FREQ-MAX, PSSO7 |
| 封装： | 10.16 X 13.77 MM, 4.57 MM HEIGHT, ROHS COMPLIANT, TO-PMOD, 7 PIN |
| 文件页数： | 22/22页 |
| 文件大小： | 1383K |
| 代理商： | LMZ10504EXTTZX |
A second criteria before finalizing the C
in bypass capacitor is
the RMS current capability. The necessary RMS current rat-
ing of the input capacitor to a buck regulator can be estimated
by
With this high AC current present in the input capacitor, the
RMS current rating becomes an important parameter. The
maximum input capacitor ripple voltage and RMS current oc-
cur at 50% duty cycle. Select an input capacitor rated for at
least the maximum calculated I
Cin(RMS).
Additional bulk capacitance with higher ESR may be required
to damp any resonance effects of the input capacitance and
parasitic inductance.
Output Capacitor Selection
In general, 22 F to 100 F high quality dielectric (X5R, X7R)
ceramic capacitor rated at twice the maximum output voltage
is sufficient given the optimal high frequency characteristics
and low ESR of ceramic dielectrics. Although, the output ca-
pacitor can also be of electrolytic chemistry for increased
capacitance density.
Two output capacitance equations are required to determine
the minimum output capacitance. One equation determines
the output capacitance (C
O) based on PWM ripple voltage.
The second equation determines C
O based on the load tran-
sient characteristics. Select the largest capacitance value of
the two.
The minimum capacitance, given the maximum output volt-
age ripple (
ΔV
OUT) requirement, is determined by the follow-
ing equation:
Where the peak to peak inductor current ripple (
Δi
L) is equal
to:
R
ESR is the total output capacitor ESR, L is the inductance
value of the internal power inductor, where L = 1.5 H, and
f
SW = 1 MHz. Therefore, per the design example:
The minimum output capacitance requirement due to the
PWM ripple voltage is:
Three miliohms is a typical R
ESR value for ceramic capacitors.
The following equation provides a good first pass capacitance
requirement for a load transient:
Where I
step is the peak to peak load step, VFB = 0.8V, and
ΔV
o_tran is the maximum output voltage deviation, which is
±20 mV.
Therefore the capacitance requirement for the given design
parameters is:
In this particular design the output capacitance is determined
by the load transient requirements.
Table 1 lists some examples of commercially available ca-
pacitors that can be used with the LMZ10504EXT.
9
www.national.com
LMZ10504EXT
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LMZ10504EXTTZX/NOPB | 功能描述:直流/直流开关转换器 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 |
| LMZ10504TZ-ADJ | 制造商:NSC 制造商全称:National Semiconductor 功能描述:4A SIMPLE SWITCHER?Power Module with 5.5V Maximum Input Voltage |
| LMZ10504TZ-ADJ/NOPB | 功能描述:直流/直流开关转换器 5V,4A PWR MODULE 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 |
| LMZ10504TZE-ADJ | 制造商:NSC 制造商全称:National Semiconductor 功能描述:4A SIMPLE SWITCHER?Power Module with 5.5V Maximum Input Voltage |
| LMZ10504TZE-ADJ/NOPB | 功能描述:直流/直流开关转换器 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 |
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