TI LED171596A 96个LED阵列驱动解决方案

电子工程师 2018-07-14 7933

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描述

TI公司的LED171596A是用于RGB和白光LED的96个（24x4） LED阵列驱动器，具有单独的通路控制，支持4个低电阻高边开关和24个低边电流沉，每路可提供多达15mA的连续电流，电流匹配度±5%，I2C，SPI和PWM亮度控制模式，具有扩展的保护功能如开路和短路LED故障检测和热关断保护。主要用在控制面板照明和局部地区调光LED背景光驱动器。本文介绍了LED171596A主要特性，功能框图和应用电路，亮度通路图以及评估板LED171596A EVM特性，电路图，材料清单和PCB设计图。

LED171596A 96-LED Matrix Driver for RGB and White LEDs.The LED171596A is a 96 channel matrix LED driverwith independent channel control， designed fordriving locally dimmed displays. The device sports 4low-resistance high side switches and 24 low side current sinks that can deliver up to 15 mA ofcontinuous current per channel. The driver has 9-bitduty cycle and 8-bit current control of each low-sideLED current sink.

Each current sink can be individually controlledthrough the I2C-compatible or SPI interface， but alsohas the capability to be controlled with a single valuethrough the global brightness control register. Thisglobal brightness control also passes through abrightness sloper function to create optically smoothbrightness transitions without the need for multipleregister writes.

The LED171596A is a LED driver that can individually control up to 96 LEDs. To control the 96 LEDs in a 4 × 24matrix the device uses four high-side PMOS switches and 24 low-side programmable current sinks. Each of thelow-side current sinks has independent 9-bit duty cycle and 8-bit current control. The individually duty and currentvalues can be controlled through the SPI or I2C-compatible interfaces.

The four high-side switches allow the LED171596A to time multiplex four groups of 24 LEDs. Maximum peakcurrent is set with ISET （with 60 mA maximum）， but the maximum average current delivered to each LED is 15mA （ILED_MAX /4）。

The individual LED brightness is internally multiplied with a global brightness register value. This allows thecontrol of all the LEDs at once with a single master brightness register or PWM input signal. This masterbrightness also passes through a brightness sloper function to create optically smooth brightness transitionswithout the need for multiple register writes.

Device control interface features：

• EN is an enable input for LED171596A

• INT is an open-drain interrupt output （indicating fault condition detection or sloper completion， for example）

• IFSEL_LATCH is a dual function pin which is used for selecting between I2C-compatible and SPI after risingedge of EN pin then can be used to latch register changes.

– For interface selection the IFSEL pin status is checked after rising edge of EN pin. Note： IFSEL must bestatic for tIFSEL_HOLD max time following EN rising edge.

– If IFSEL is pulled low （0） the 4-wire SPI interface is selected （SCLK， MISO， MOSI， and SS）。

– If IFSEL is pulled high （1） the 2-wire I2C-compatible interface is selected.

– An optional PWM input is available at SS/PWM when I2C is selected.

– When I2C is selected， the ADDR pin is used to select between three alternate I2C slave addresses.

– In normal mode the pin functions as a LATCH signal to trigger updates of SRAM buffers.

– LATCH occurs on the rising edge. Minimum latch pulse length is tLATCH ns.

– Alternatively a LATCH register bit can be used instead of pin control. Wait for latch_busy to be clearedin STATUS register before writing to SRAM when using LATCH register bit.

• ISET pin to set master LED current level for all LEDs.

Protection features of the LED171596A device include：

• Open-LED and shorted-LED detections

– When detected （unless masked）， the INT pin goes low， and status registers show that LEDs are OPEN orSHORT. Faulty LEDs can then be disabled via register bits， and fault status can be cleared.

• Thermal shutdown in case of die overtemperature.

LED171596A主要特性：

1• 24 High-Precision Current Sinks

– 60-mA Peak Current per Channel

– Current Matching ±5%

– Independent 9-Bit Duty Cycle PWM and 8-BitLED Current Control

– 7-V Tolerant

– ISET Resistor to Set Global Current

– Ghosting Cancellation

• Four Low Resistance High Side Series Switches

– 1.5-A Current-Rated PMOS

• I2C， SPI， and PWM Brightness Control Modes

• Extensive Protection Features

– Open and Shorted LED Fault Detection

– Thermal Shutdown Protection

LED171596A应用：

• Control Panel Illumination

• Local Dimming LED Backlight Drivers

LED阵列

图1.LED171596A功能框图

LED阵列

图2.LED171596A简化电路图

LED阵列

图3.LED171596A典型应用电路图

LED阵列

图4.LED171596A亮度通路图

评估板LED171596A EVM

The Texas Instruments LED171596A evaluation module （EVM） helps designers evaluate the operationand performance of the LED171596A 96-LED driver. The LED171596A is an LED matrix driver that canindividually control up to 96 LEDs. To control the 96 LEDs it uses four high-side PMOS switches and 24low-side programmable current sinks. The driver has 9-bit duty cycle and 8-bit current control of each lowside LED current sink. They can be individually controlled through the I2C-compatible or SPI interface.The EVM contains one LED171596A and one LEDARRAYEVM with 96 white LEDs.

图5.评估板LED171596A EVM外形图

LED阵列