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参数资料
| 型号： | MAX8654EVKIT+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 12/17页 |
| 文件大小： | 0K |
| 描述： | EVAL KIT MAX8654, MAX8688 |
| 标准包装： | 1 |
| 系列： | * |
12V, 8A 1.2MHz
Step-Down Regulator
Undervoltage Lockout (UVLO)
The UVLO circuitry inhibits switching when V IN or V VDL
is below 4.20V (typ) or V VL is below 3V. Once these
voltages are above the thresholds, UVLO clears and
the soft-start function activates; 100mV of hysteresis is
built in for glitch immunity.
High-Side MOSFET Driver Supply (BST)
The gate-drive voltage for the high-side, n-channel
switch is generated by a flying capacitor boost circuit.
The capacitor between BST and LX is charged from the
VDL supply while the low-side MOSFET is on. When the
low-side MOSFET is switched off, the stored voltage of
the capacitor is stacked above LX to provide the neces-
sary turn-on voltage for the high-side internal MOSFET.
Frequency Select (FREQ)
The switching frequency in fixed-frequency PWM oper-
ation is resistor programmable from 250kHz to 1.2MHz.
Set the switching frequency of the IC with a resistor
(R FREQ ) from FREQ to GND. R FREQ is calculated as:
Shutdown Mode
Drive EN to GND to shut down the IC and reduce qui-
escent current to 10μA (typ). During shutdown, the out-
puts of the MAX8654 are high impedance. Drive EN
high to enable the MAX8654.
Thermal Protection
Thermal-overload protection limits total power dissipa-
tion in the device. When the junction temperature
exceeds T J = +165°C, a thermal sensor forces the
device into shutdown, allowing the die to cool. The ther-
mal sensor turns the device on again after the junction
temperature cools by 20°C, causing a pulsed output
during continuous overload conditions. The soft-start
sequence begins after a thermal-shutdown condition.
Applications Information
VL and VDL Decoupling
To decrease the noise effects due to the high switching
frequency and maximize the output accuracy of the
MAX8654, decouple VDL with a minimum of 2.2μF
R FREQ = 52 . 63 × ?
? 0 . 05 ? k ?
? 1
? f S
?
?
ceramic capacitor from VDL to PGND. Also, decouple
VL with a 1μF ceramic capacitor from VL to GND. Place
these capacitors as close to the respective pins as pos-
sible.
where f S is the desired switching frequency in MHz.
SYNC Function (SYNC, SYNCOUT)
Inductor Selection
Choose an inductor with the following equation:
The MAX8654 features a SYNC function that allows the
switching frequency to be synchronized to any external
clock frequency that is higher than the internal clock
frequency. Drive SYNC with a square wave at the
L =
V OUT x ( V IN ? V OUT )
f S x V IN x LIR x I OUT ( MAX )
desired synchronization frequency. A rising edge on
SYNC triggers the internal SYNC circuitry. Connect
SYNC to GND to disable the function and operate with
the internal oscillator.
The SYNCOUT output generates a clock signal that is
180° out-of-phase with its internal oscillator, or the sig-
nal applied to SYNC. This allows for another MAX8654
to be synchronized 180° out-of-phase to reduce the
input ripple current.
Power-Good Output (PWRGD)
where LIR is the ratio of the inductor ripple current to
average continuous current at the minimum duty cycle.
Choose LIR between 20% to 40% for best performance
and stability.
Use a low-loss inductor with the lowest possible DC
resistance that fits in the allotted dimensions. Powered
iron-ferrite core types are often the best choice for per-
formance. With any core material, the core must be
large enough not to saturate at the peak inductor cur-
rent (I PEAK ). Calculate I PEAK as follows:
PWRGD is an open-drain output that goes high imped-
ance once the soft-start ramp has concluded, provided
V REFIN is above 0.54V and V FB is greater than 90% of
I PEAK = ( 1 +
LIR
2
) x I OUT ( MAX )
V REFIN . PWRGD pulls low when V FB is less than 90% of
V REFIN and V REFIN is less than 0.54V for 48 clock
cycles. PWRGD is low during shutdown, when pulled up
to V VL .
12
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX8654EVKIT+ | 功能描述:电源管理IC开发工具 MAX8654 Eval Kit RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| MAX8655ETN/GG8 | 功能描述:直流/直流开关调节器 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 |
| MAX8655ETN+ | 功能描述:直流/直流开关调节器 25A Int MOSFET Step-Down 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 |
| MAX8655ETN+T | 功能描述:直流/直流开关调节器 25A Int MOSFET Step-Down 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 |
| MAX8655ETN+TW | 功能描述:直流/直流开关调节器 25A Int MOSFET Step-Down 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 |
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