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参数资料
| 型号： | MAX5072EVKIT |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 18/27页 |
| 文件大小： | 0K |
| 描述： | EVAL KIT FOR MAX5072 |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 1 |
| 主要目的： | DC/DC，步升/步降 |
| 输出及类型： | 2，非隔离 |
| 输出电压： | 3.3V，12V |
| 电流 - 输出： | 2A，220mA |
| 输入电压： | 5.5 ~ 16 V |
| 稳压器拓扑结构： | 降压-升压 |
| 频率 - 开关： | 2.2MHz |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | MAX5072 |
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2.2MHz, Dual-Output Buck or Boost
Converter with POR and Power-Fail Output
R A C ?
? V FB ? V OUT ?
? V BYPASS FB ?
? V ESR
? I OUT +
2 ?
?
For output voltages below 0.8V, set the MAX5072 out-
put voltage by connecting a voltage-divider from the
output to FB_ to BYPASS (Figure 6). Select R C (FB to
BYPASS resistor) higher than a 50k ? range. Calculate
R A with the following equation:
= R ?
? V
where V FB = 0.8V, V BYPASS = 2V (see the Electrical
Characteristics table), and V OUT_ can range from 0V to
V FB_ .
Inductor Selection
Three key inductor parameters must be specified for
operation with the MAX5072: inductance value (L), peak
inductor current (I L ), and inductor saturation current
(I SAT ). The minimum required inductance is a function of
operating frequency, input-to-output voltage differential
and the peak-to-peak inductor current ( ? I L ). Higher ? I L
allows for a lower inductor value while a lower ? I L
requires a higher inductor value. A lower inductor value
minimizes size and cost, improves large-signal transient
response, but reduces efficiency due to higher peak cur-
rents and higher peak-to-peak output ripple voltage for
the same output capacitor. On the other hand, higher
inductance increases efficiency by reducing the ripple
current. However, resistive losses due to extra wire turns
can exceed the benefit gained from lower ripple current
levels, especially when the inductance is increased with-
out also allowing for larger inductor dimensions. A good
compromise is to choose ? I L equal to 30% of the full
Input Capacitors
The discontinuous input current waveform of the buck
converter causes large ripple currents at the input. The
switching frequency, peak inductor current, and the
allowable peak-to-peak voltage ripple dictate the input
capacitance requirement. Increasing the switching fre-
quency or the inductor value lowers the peak to aver-
age current ratio, yielding a lower input capacitance
requirement. Note that two converters of MAX5072 run
180° out-of-phase, thereby effectively doubling the
switching frequency at the input.
The input ripple waveform would be unsymmetrical due
to the difference in load current and duty cycle between
converter 1 and converter 2. The input ripple is com-
prised of ? V Q (caused by the capacitor discharge) and
? V ESR (caused by the ESR of the capacitor). A higher
load converter dictates the ESR requirement, while the
capacitance requirement is a function of the loading
mismatch between the two converters. The worst-case
mismatch is when one converter is at full load while the
other is at no load or in shutdown. Use low-ESR ceramic
capacitors with high ripple-current capability at the
input. Assume the contribution from the ESR and capac-
itor discharge equal to 50%. Calculate the input capaci-
tance and ESR required for a specified ripple using the
following equations:
ESR IN =
? ? I L ?
?
where
load current. To calculate the inductance use the follow-
ing equation:
? I L =
( V IN ? V OUT ) × V OUT
V IN × f SW × L
L =
V OUT ( V IN ? V OUT )
V IN × f SW × ? I L
and
where V IN and V OUT are typical values (so that efficiency
is optimum for typical conditions). The switching frequen-
cy is set by R OSC (see the Setting the Switching
Frequency section). The peak-to-peak inductor current,
which reflects the peak-to-peak output ripple, is worst at
where
C IN =
I OUT × D ( 1 ? D )
? V Q × f SW
D = OUT
the maximum input voltage. See the Output Capacitor
Selection section to verify that the worst-case output rip-
ple is acceptable. The inductor saturating current is also
important to avoid runaway current during the output
overload and continuous short circuit. Select the I SAT to
be higher than the maximum peak current limits of 4.5A
and 2.2A for converter 1 and converter 2.
V
V IN
where I OUT is the maximum output current from either
converter 1 or converter 2, and D is the duty cycle for
that converter. f SW is the frequency of each individual
converter. For example, at V IN = 12V, V OUT = 3.3V at
I OUT = 2A, and with L = 3.3μH, the ESR and input
capacitance are calculated for a peak-to-peak input
18
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX5073 | 制造商:MAXIM 制造商全称:Maxim Integrated Products 功能描述:2.2MHz, Dual-Output Buck or Boost Converter with Internal Power MOSFETs |
| MAX5073ATI | 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 |
| MAX5073ATI+ | 功能描述:直流/直流开关转换器 2.2MHz Buck or Boost Converter 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 |
| MAX5073ATI+T | 功能描述:直流/直流开关转换器 2.2MHz Buck or Boost Converter 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 |
| MAX5073ATI-T | 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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