原标题：Microchip MIC28517同步降压控制器评估方案

　　microchip公司的MIC28517可调频率同步降压稳压器,具有自适应开态控制架构.输入电源电压从4.5V到70V,稳压输出电流高达8A.输出电压可调低至0.6V,精度±1%.超高速控制架构允许具有超快瞬态响应而降低了输出电容,使得高VIN/低VOUT工作成为可能.这种自适应开态控制架构在单个器件组合了固定频率工作和快速瞬态响应.轻负载下的工作模式可选择;也可提供超轻负载模式和连续导通模式.而HLL模式比轻负载条件下的CCM有更高的效率.而CCM在整个负载范围内几乎保持开关频率不变. MIC28517的保护特性包括欠压锁住(UVLO),软起动以降低浪涌电流,打嗝模式短路保护和热关断.可调开关频率从270kHz到800kHz,内部具有补偿,内置身V稳压器可用于单电源工作,辅助的自举LDO用来改善系统效率.工作温度-40C 到 +125C,26引脚6mmx6mm VQFN封装.主要用在案分布式电源系统,通信/网络基础设备,工业用电报挂号源和太阳能.本文介绍了MIC28517主要特性,功能框图和应用电路,以及MIC28517评估板主要特性,电路图,材料清单和PCB设计图.

　　The MIC28517 is an adjustable frequency, synchro-nous buck regulator that features a unique adaptive on-time control architecture. The MIC28517 operatesover an input supply range of 4.5V to 70V and providesa regulated output of up to 8A of output current. The output voltage is adjustable down to 0.6V, with anaccuracy of ±1%.Hyper Speed Control architecture allows for an ultra-fast transient response, while reducing the output capacitance, and also makes high-VIN/low-VOUT operation possible. This adaptive on-time control architecture combines the advantages of fixed frequency operation and fast transient response in a single device.The operating mode under light load conditions is select-able; HyperLight Load mode and Continuous Conduction Mode are available. HLL mode results in higher efficiency than that of the CCM under light load conditions, while the CCM keeps the switching frequency almost constantover the entire load current range.The MIC28517 offers a full suite of features thatensures the protection of the Integrated Circuit (IC)during Fault conditions. These features include Under-voltage Lockout (UVLO) to ensure proper operationunder power sag conditions, soft start to reduce inrushcurrent, Hiccup mode short-circuit protection andthermal shutdown.

　　MIC28517主要特性:

　　• Hyper Speed Control® Architecture Enables:

　　- High input to output voltage conversion ratio capability (VIN = 70V and VOUT = 0.6V)

　　- Small output capacitance

　　• 4.5V to 70V Input Voltage

　　• 8A Output Current Capability with Up to 95% Efficiency

　　• Adjustable Output Voltage from 0.6V to 32V

　　• Selectable HyperLight Load® (HLL) or Continuous Conduction Mode (CCM) Operation

　　• ±1% FB Accuracy

　　• Any Capacitor™ Stable:

　　- Zero-ESR to High-ESR output capacitors

　　• 270 kHz to 800 kHz Adjustable Switching Frequency

　　• Internal Compensation

　　• Built-in 5V Regulator for Single-Supply Operation

　　• Auxiliary Bootstrap LDO for Improving System Efficiency

　　• Internal Bootstrap Diode

　　• Programmable Current Limit

　　• “Hiccup” Mode Short-Circuit Protection

　　• Thermal Shutdown

　　• Supports Safe Start-up into a Pre-Biased Output

　　• -40C to +125C Junction Temperature Range

　　• Available in 32-Pin, 6 mm x 6 mm VQFN Package

　　MIC28517应用:

　　• Distributed Power Systems

　　• Communications/Networking Infrastructure

　　• Industrial Power Supplies

　　• Solar Energy

　　图1. MIC28517功能框图

　　图2. MIC28517典型应用电路图

　　MIC28517评估板

　　The MIC28517 Evaluation Board is a constant frequency, synchronous buck controller

　　featuring a unique adaptive on-time control architecture. The MIC28517 operates over

　　an input supply range of 4.5V to 70V. The output voltage is adjustable down to 0.6V

　　with an ensured accuracy of ±1%. The device operates with a programmable switching

　　frequency from 270 kHz to 800 kHz. The Mode pin allows the user to select either the

　　forced CCM operation or HLL mode of operation for improved efficiency at light loads.

　　The MIC28517 Evaluation Board requires only a single power supply with at least 8A

　　current capability. The MIC28517 has an internal VDD LDO so no external linear regulator

　　is required to power the internal biasing of the IC. In applications with VIN < +5.5V,

　　PVDD should be tied to PVIN to bypass the internal linear regulator. The output load can

　　either be a passive or an active load.

　　图3. MIC28517评估板外形图

　　MIC28517评估板主要特性:

　　• Features a Mode selection pin through jumper J6, which allows the user to select either the CCM or HLL mode of operation.

　　• Features six selectable output voltages: 0.8V, 1.2V, 2.5V, 3.3V, 5V and 12V.

　　• Features an auxiliary bootstrap Low Dropout (LDO) which improves the system efficiency by supplying the internal bias power from the output of the converter.

　　• Features a logic level Enable (EN) signal that can be used to enable or disable the controller.

　　• Can start up monotonically into a pre-biased output.

　　• Features an open-drain Power Good signal (PG), which signals when the output is in regulation.

　　The basic parameters of the evaluation board are:

　　• Input: 10V to 70V (optimized for 48V)

　　• Output: 0.8V, 1.2V, 2.5V, 3.3V, 5V or 12V Selectable through jumper J10 at 8A (default option is set to 5V)

　　• 270 kHz Switching Frequency (adjustable from 270 kHz to 800 kHz)

　　The MIC28517 Evaluation Board includes the following items:

　　• MIC28517 Evaluation Board (ADM00995)

　　• Important Information Sheet

　　图4.MIC28517评估板电路描述图

　　图5.MIC28517评估板电路电路图