LT8646SA

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65V, 8A Synchronous Step-Down Silent Switcher 2 with 2.5μA Quiescent Current

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产品技术资料帮助

ADI公司所提供的资料均视为准确、可靠。但本公司不为用户在应用过程中侵犯任何专利权或第三方权利承担任何责任。技术指标的修改不再另行通知。本公司既没有含蓄的允许，也不允许借用ADI公司的专利或专利权的名义。本文出现的商标和注册商标所有权分别属于相应的公司。
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概述

  • Silent Switcher®2 Architecture
    • Ultralow EMI Emissions on Any PCB
    • Eliminates PCB Layout Sensitivity
    • Internal Bypass Capacitors Reduce Radiated EMI
    • Optional Spread Spectrum Modulation
  • High Efficiency at High Frequency 
    • Up to 94% Efficiency at 400kHz, 24VIN to 5VOUT
    • Up to 93% Efficiency at 1MHz, 24VIN to 5VOUT
  • Wide Input Voltage Range: 3.4V to 65V
  • Wide Output Voltage Range: 0.97V to (VIN - 0.5V)
  • Ultralow Quiescent Current Burst Mode Operation
    • 2.5μA IQ Regulating 12VIN to 3.3VOUT (LT8645SA)
    • Output Ripple < 10mVP-P
  • External Compensation: Fast Transient Response and Current Sharing (LT8646SA)
  • Robust High VOUT Operation
    • Safely Tolerates High Reverse Current
  • Fast Minimum Switch On-Time: 40ns
  • Low Dropout Under All Conditions: 60mV at 1A
  • Adjustable and Synchronizable: 200kHz to 2.2MHz
  • Output Soft-Start and Tracking
  • Small 32-Lead 6mm × 4mm LQFN Package
  • AEC-Q100 Qualified for Automotive Applications

The LT®8645SA/LT8646SA synchronous step-down regulator features second generation Silent Switcher architecture designed to minimize EMI emissions while delivering high efficiency at high switching frequencies. This includes the integration of bypass capacitors to optimize all the fast current loops inside and make it easy to achieve advertised EMI performance by eliminating layout sensitivity.

The fast, clean, low-overshoot switching edges enable high efficiency operation even at high switching frequencies, leading to a small overall solution size. Peak current mode control with a 40ns minimum ontime allows high step-down ratios even at high switching frequencies. The LT8646SA has external compensation to enable current sharing and fast transient response at high switching frequencies.

Burst Mode® operation enables ultralow standby current consumption, forced continuous mode can control frequency harmonics across the entire output load range, or spread spectrum operation can further reduce EMI emissions.

APPLICATIONS

  • Automotive and Industrial Supplies
  • General Purpose Step-Down
LT8646SA
65V, 8A Synchronous Step-Down Silent Switcher 2 with 2.5μA Quiescent Current
LT8645SA Simplified Application Diagram LT8646SA Pin Configuration LT8646SA Chip Illustration
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工具及仿真模型

LTspice

LTspice中提供以下器件型号：

  • LT8646S

LTpowerCAD

LTpowerCAD中提供以下器件的设计工具：

  • LT8646S
LTspice

LTspice®是一款强大高效的免费仿真软件、原理图采集和波形观测器，为改善模拟电路的仿真提供增强功能和模型。

评估套件

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schematic 1
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schematic 3
EVAL-LT8646SA-AZ

65V, 8A Synchronous Step-Down Silent Switcher 2

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产品详情

The evaluation circuit EVAL-LT8646SA-AZ is a 65V, 8A synchronous step-down second generation Silent Switcher® with spread spectrum frequency modulation featuring the LT8646SA. The evaluation board is designed for 5V output from a 5.6V to 65V input. The wide input range allows a variety of input sources, such as automotive batteries and industrial supplies. The LT8646SA is a compact, ultralow emission, high efficiency, and high speed synchronous monolithic step-down switching regulator. The integrated bypass capacitors optimize all the fast current loops and make it easier to minimize EMI/EMC emissions by reducing layout sensitivity. Selectable spread spectrum mode can further improve EMI/EMC performance. Fast minimum on-time of 40ns enables high VIN to low VOUT conversion at high frequency.

The LT8646SA switching frequency can be programmed either through oscillator resistor or external clock over a 200kHz to 2.2MHz range. The default frequency of EVAL-LT8646SA-AZ is 2MHz. The SYNC pin on the demo board is grounded (JP1 at BURST position) by default for low ripple Burst Mode operation. To synchronize to an external clock, move JP1 to SYNC and apply the external clock to the SYNC terminal. Select the spread spectrum mode and forced continuous mode (FCM), respectively, by moving the JP1 shunt. Figure 1 in the User Guide shows the efficiency of the circuit at 12V input and 24V input in Burst Mode operation (input from VIN terminal to bypass the EMI filter). Figure 2 in the User Guide shows the LT8646SA temperature rising on EVAL-LT8646SA-AZ board under different load conditions. The rated maximum load current is 8A, while derating is necessary for certain input voltage and thermal conditions. Low switching frequency can extend the output load capability by reducing the power dissipation. Figure 3 in the User Guide shows the temperature rising at 400kHz switching frequency.

Please see the User Guide for the full description.
EVAL-LT8646SA-AZ
65V, 8A Synchronous Step-Down Silent Switcher 2
EVAL-LT8646SA-AZ Board Photo Angle View EVAL-LT8646SA-AZ Board Photo Top View EVAL-LT8646SA-AZ Board Photo Bottom View

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