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参数资料
| 型号： | SP7656EB |
| 厂商： | Exar Corporation |
| 文件页数： | 6/10页 |
| 文件大小： | 0K |
| 描述： | EVAL BOARD FOR SP7656 |
| 标准包装： | 1 |
| 系列： | * |
? V , Cin ?
the capacitor discharges linearly as it supplies
I OUT -I in . The contribution to Input voltage ripple
by each term can be calculated from:
Iout Vout ( Vin ? Vout )
fs Cin Vin 2
? V , ESR ? ESR ? Iout ? 0 . 5 Irip ?
provides a satisfactory method for calculating
C OUT . Select ESR such that output voltage
ripple (V RIP ) specification is met. There are two
components to the output ripple voltage: The
first component arises from charge transferred
to and from C OUT during each cycle. The
second component is due to inductor ripple
current flowing through the output capacitor’s
ESR. It can be calculated from:
ESR ? ? ?
? ?
? V , ESL ? ESL
? Iout ? 0 . 5
Trise
Irip
?
Vrip ? Irip
2 ? 1 ?
? 8 Cout fs ?
2
current I OUT corresponds to inductor stored
energy of ? L I OUT .
Where Trise is the rise time of current through
Capacitor. The total input voltage ripple is sum
of the above:
Output Capacitor Selection
Select the output capacitor for voltage rating,
capacitance and Equivalent Series Resistance
(ESR).
Nominally the voltage rating is selected to be
twice as large as the output voltage. Select the
capacitance to satisfy the specification for
output voltage overshoot/undershoot caused
by current step load. A steady-state output
2
Where:
I RIP is inductor ripple current
f s is switching frequency
C OUT is output capacitor calculated above
Note that a smaller inductor results in a higher
inductor ripple current, therefore requiring a
larger C OUT and/or lower ESR in order to meet
the output voltage ripple requirement.
Schottky Rectifier Selection
Select the Schottky based on the voltage
rating VR, Forward voltage V f , and thermal
resistance R thja . For a low duty cycle
application the Schottky is conducting most of
the time and its conduction losses are the
largest component of losses in the converter.
Conduction losses can be estimated from:
Pc ? Vf Iout ? 1 ?
?
A sudden decrease in I OUT forces the energy
surplus in L to be absorbed by C OUT . This
causes an overshoot in output voltage that is
corrected by the power switch reducing in duty
cycle. Use the following equation to calculate
C OUT :
where:
?
?
Vout ?
Vin ?
I 2 ? I 1
? ?
Cout ? L ?
2 ?
Vos ? Vout ?
?
2 2
? ?
2
Where:
L is the output inductance
I2 is the step load high current
I1 is the step load low current
V os is output voltage including overshoot
V OUT is steady state output voltage
Output voltage undershoot calculation is more
complicated. Test results for SP7656 buck
circuits show that undershoot is approximately
equal to overshoot. Therefore above equation
11/07/08 SP7656 PowerBlox
6
V f is diode forward voltage at I OUT
The AC losses from the switching capacitance
of a Schottky are negligible and can be
ignored.
? Copyright 2008 EXAR Corporation
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相关代理商/技术参数 |
参数描述 |
|---|---|
| SP7656EN2-L | 功能描述:开关变换器、稳压器与控制器 NonSync 600kHz High Input DC/DC Volt Reg RoHS:否 制造商:Texas Instruments 输出电压:1.2 V to 10 V 输出电流:300 mA 输出功率: 输入电压:3 V to 17 V 开关频率:1 MHz 工作温度范围: 安装风格:SMD/SMT 封装 / 箱体:WSON-8 封装:Reel |
| SP7656EN2-L/TR | 功能描述:开关变换器、稳压器与控制器 600KHZ HIGH INPUT NON-SYNC STEP DWN RoHS:否 制造商:Texas Instruments 输出电压:1.2 V to 10 V 输出电流:300 mA 输出功率: 输入电压:3 V to 17 V 开关频率:1 MHz 工作温度范围: 安装风格:SMD/SMT 封装 / 箱体:WSON-8 封装:Reel |
| SP7661 | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Evaluation Board Manual |
| SP7661_07 | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Wide Input Voltage Range 3A, 600kHz, Buck Regulator |
| SP7661_1 | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:Evaluation Board Manual |
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