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| 型号： | SP7652EB |
| 厂商： | Exar Corporation |
| 文件页数： | 10/15页 |
| 文件大小： | 0K |
| 描述： | EVAL BOARD FOR SP7652 |
| 标准包装： | 1 |
| 系列： | * |
S P 7 6 5 2
P o w e r b l o x T M
6 A 2 8 V 6 0 0 K H z S y n c h r o n o u s S t e p D o w n R e g u l a t o r
neglected at higher output currents where the
copper losses dominate. Core loss information
is usually available from the magnetics
vendor. Proper inductor selection can affect
the resulting power supply efficiency by more
than 15-20%!
The copper loss in the inductor can be
calculated
using the following equation:
where:
ΔV OUT = Peak-to-Peak Output Voltage Ripple
I PK-PK = Peak-to-Peak Inductor Current
The total output ripple is a combination of the
ESR and the output capacitance value and can
be calculated as follows:
P L(CU) = I 2L(RMS) R WINDING
where I L(RMS) is the RMS inductor current that
can be calculated as follows:
F S = Switching Frequency
D = Duty Cycle
C OUT = Output Capacitance Value
O UTPUT C APACITOR S ELECTION
The required ESR (Equivalent Series
Resistance) and capacitance drive the
selection of the type and quantity of the
output capacitors. The ESR must be small
enough that both the resistive voltage
deviation due to a step change in the load
current and the output ripple voltage do not
exceed the tolerance limits expected on the
output voltage. During an output load
transient, the output capacitor must supply all
the additional current demanded by the load
until the SP7652 adjusts the inductor current
to the new value.
In order to maintain V OUT , the capacitance
must be large enough so that the output
voltage is held up while the inductor current
ramps up or down to the value corresponding
to the new load current. Additionally, the ESR
in the output capacitor causes a step in the
output voltage equal to the current. Because
of the fast transient response and inherent
100% to 0% duty cycle capability provided by
the SP7652 when exposed to output load
transient, the output capacitor is typically
chosen for ESR, not for capacitance value.
The ESR of the output capacitor, combined
with the inductor ripple current, is typically the
main contributor to output voltage ripple. The
maximum allowable ESR required to maintain
a specified output voltage ripple can be
calculated by:
I NPUT C APACITOR S ELECTION
The input capacitor should be selected for
ripple current rating, capacitance and voltage
rating. The input capacitor must meet the
ripple current requirement imposed by the
switching current. In continuous conduction
mode, the source current of the high-side
MOSFET is approximately a square wave of
duty cycle V OUT /V IN . Most of this current is
supplied by the input bypass capacitors. The
RMS value of input capacitor current is
determined at the maximum output current
and under the assumption that the peak to
peak inductor ripple current is low; it is given
by:
I CIN(RMS) = I OUT(MAX) √D(1 -D)
The worse case occurs when the duty cycle D
is 50% and gives an RMS current value equal
to I OUT /2.
Select input capacitors with adequate ripple
current rating to ensure reliable operation.
The power dissipated in the input capacitor is:
P CIN =I 2CIN(RMS) R ESR(CIN)
This can become a significant part of power
losses in a converter and hurt the overall
energy transfer efficiency. The input voltage
ripple primarily depends on the input capacitor
ESR and capacitance. Ignoring the inductor
? 2012 Exar Corporation
10/15
Rev. 2.0.0
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相关代理商/技术参数 |
参数描述 |
|---|---|
| SP7652ER | 制造商:Rochester Electronics LLC 功能描述: 制造商:Exar Corporation 功能描述: |
| SP7652ER/TR | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Wide Input Voltage Range 6A, 600kHz, Buck Regulator |
| SP7652ERL | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Wide Input Voltage Range 6A, 600kHz, Buck Regulator |
| SP7652ER-L | 功能描述:电压模式 PWM 控制器 Buck Regulator RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| SP7652ERL/TR | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Wide Input Voltage Range 6A, 600kHz, Buck Regulator |
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