摘要: ADI公司的LTM8005是38VIN 38VOUT的升压电源微模块(μModule)LED驱动器,固定频率和电流模式架构使得大范围的电源和输出电压内具有稳定工作,广谱频率调制(SSFM)可以改善电磁兼容(EMC)性能,输入电压5-38V,支持升压或SEPIC电源拓扑,可调LED电流高达1.6A,集成了40V 10A功率开关,3000:1真彩色PWM调光,工作温度–40℃ - 150℃,主要用在大功率LED和高压LED,以及精密限流的电压稳压器.本文介绍了LTM8005主要特性,功能框图,多种应用电路,以及演示板DC2257A主要特性,测量建立图,电路图,材料清单.
The LTM.8005 is a 38VIN, 38VOUT boost μModule (power micromodule) LED driver designed to regulate current or voltage and is ideal for driving LEDs. The fixed frequency and current mode architecture result in stable operation over a wide range of supply and output voltages. Spread spectrum frequency modulation (SSFM) can be activated for improved electromagnetic compatibility (EMC) performance.
The ground-referred voltage FB pin serves as the input for several LED protection features, and also allows the converter to operate as a constant voltage source. The PWM input provides LED dimming ratios of up to 3000:1, and the CTRL inputs provide additional analog dimming capability.
The low profile package enables utilization of unused space on the bottom of PC boards. The LTM8005 is packaged in thermally enhanced, compact over-molded Ball Grid Array (BGA) package suitable for automated assembly by standard surface mount equipment. The LTM8005 is RoHS compliant.
Wide Input Voltage Range: 5V to 38V
Supports Boost or SEPIC Power Topologies
Adjustable LED Current Up to 1.6A
40V 10A Internal Power Switch
Wide Temperature Range: –40℃to 150℃
Input and Output Current Reporting
Internal Switch for PWM and Output Disconnect
Internal Spread Spectrum Frequency Modulation
3000:1 True Color PWM™ Dimming
Open LED Protection with OPENLED Flag
Short-Circuit Protection and SHORTLED Flag
Soft-Start with Programmable Fault Restart Timer
9mm × 11.25mm × 2.22mm BGA
nn High Power LED, High Voltage LED
nn Accurate Current-Limited Voltage Regulators
Demonstration circuit 2257A features the LTM®8005 – a 38VIN, 38VOUT boost μModule® LED driver that can disconnect the output to protect against faults and provides spread spectrum switching to simplify emissions compliance. DC2257A is an LED driver with an input range for normal operation from 6V to 27V. OVLO becomes active for inputs above 29V and the maximum input voltage is 38V. The LED current is 1.2A and the base switching frequency is 350kHz. The efficiency is 92% when the input is 12V with a 35V LED load. 35V is the maximum LED voltage.
The demo circuit requires application of an external voltage to the PWM terminal for operation. The external voltage can be a DC level or an appropriate PWM dimming signal. Common frequencies for PWM dimming are 100Hz or higher. Analog dimming is achieved using the CTRL inputs.
DC2257A allows adjustments to output voltage, output current, input current, switching frequency, frequency modulation rate including disable, feedback loop compensation, EN/UVLO threshold, OVLO threshold, soft-start period, and fault latch-off or hiccup. In most cases, adjustment is made by modifying the appropriate resistor or capacitor component(s).
DC2257A provides outputs for input and output current monitoring and fault status for short and open LEDs.
The demo circuit is designed to be easily reconfigured to buck mode, buck-boost mode and SEPIC topologies. There are placeholders to mount optional LC input filter components.
The LTM8005 data sheet must be read in conjunction with this demo manual to properly use or modify DC2257A.