TI TPS92518HV：双通道SPI接口LED降压控制器

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"TI-TPS92518HV.pdf" TI-TPS92518HV是一款由德州仪器（Texas Instruments）推出的双通道降压（Buck）LED控制器，设计用于处理宽输入电压范围（6.5V至65V）的应用。这款芯片集成了一种具有高带宽、准迟滞控制特性的电路，使其能够高效稳定地驱动LED负载。该控制器包含两个独立的Buck通道，每个通道都能对LED电流进行精确控制。每个通道都具备可调节的高侧感测功能，允许用户根据应用需求定制LED电流。此外，它们还支持直接PWM（脉宽调制）调光输入，提供循环电流限制以确保系统安全。 TI-TPS92518HV的一大亮点是其SPI（串行外围接口）通信接口。通过SPI，用户可以软件配置8位的设定点，实现数字校准和分档，这使得该控制器能适应不同的LED串配置和亮度需求。同时，SPI接口还用于故障监控和报告，提供系统状态的实时反馈。在调光性能方面，TPS92518HV表现出色。它支持高达10,000:1的PWM调光范围，以及255:1的模拟调光范围，这意味着用户可以通过微调PWM信号或模拟信号的幅度来实现精细的亮度控制。此外，它还支持高频率操作，这有助于减少电磁干扰并提高系统的整体效率。在系统设计中，该控制器通过EN/UV引脚提供使能和欠压保护功能，PWM1和PWM2引脚分别用于两个独立通道的PWM调光控制。µC（微控制器）可以与MCU（微处理器单元）配合，通过SPI接口对控制器进行编程和管理。VCC引脚为控制器供电，而VLED1和VLED2则用于设置各LED通道的输出电压。 TI-TPS92518HV是一款高度集成、高性能的LED驱动控制器，适用于需要宽输入电压范围、灵活调光选项和高级故障检测功能的照明应用。其强大的功能集和SPI接口使其在智能照明解决方案中尤为突出。用户可以根据具体的设计需求，利用其丰富的特性来优化系统的效率、稳定性和亮度控制。

TPS92518

SLUSCR7 –MAY 2017

www.ti.com

Product Folder Links: TPS92518

8 Detailed Description

8.1 Overview

The TPS92518 is a Dual Channel Buck LED controller with SPI Interface. Quasi-hysteretic operation allows a

high control bandwidth and is ideal for Shunt FET and Matrix applications (series LED switched network). Internal

DACs control the high-side differential peak current sense threshold, the peak-to-peak ripple (off-time) and the

maximum off-time.

The high-side differential peak current sense threshold trip voltage is set via a 10:1 divider. The divider allows a

lower sense voltage for improved efficiency while still allowing a practical control voltage. The device uses a

controlled off-time (COFT) architecture to allow the converter to operate in both continuous conduction mode

(CCM) and discontinuous conduction mode (DCM) with no external control loop compensation, and provides an

inherent cycle-by-cycle current limit because of the peak current detection each cycle. Once an off-time (us·V)

target is digitally programmed, analog circuitry adjusts the off-time to maintain a constant peak-to-peak ripple.

Since the peak and ripple are fixed, regulation is maintained. The programmable off-time also controls the

switching frequency target.

The digitally controlled analog peak current sense threshold allows analog dimming of the LED current over the

full output range. The PWM dimming input allows for high-frequency PWM dimming control requiring no external

components. An internal configurable maximum off-timer allows for easy implementation of external shunt FET

dimming. Refer to shunt FET dimming information.This simple regulator contains all the features necessary to

implement a high-efficiency, versatile, digitally controlled, high-performance LED driver.

OFF

[LEDx_PKTH_DAC]

and R

SENSE

adjust

the peak inductor

current

The Inductance (L)

and t

OFF

define 'I

L-PP

The average output current =

the peak ± ½ the peak to peak

inductor ripple

L(pk)

SENSE

[LEDx _PKTH _DAC]

1000* R

LED OFF

L PP

V * t



AVE

L PP

L LED L(pk)

I I I



1 2 3

TPS92518

SLUSCR7 –MAY 2017

www.ti.com

Product Folder Links: TPS92518

8.3 Feature Description

8.3.1 General Operation

The TPS92518 operates using a peak-current, constant off-time control as described in Figure 16 . Two states

dictate the high-side FET control. The switch turns on and stays on until the programmed peak current is

reached. The peak current is controlled by monitoring the voltage across the sense resistor. When the voltage

drop is higher than the programmed threshold, the peak current is reached. The switch is then turned OFF,

which initiates an off-time period. An internal capacitor is then charged by a current source which varies in

relation to the VLEDx pin voltage. When the capacitor voltage reaches the DAC controlled threshold, the off-time

ends. The off-time capacitor resets and the main switch turns ON, starting the next ON cycle.

Figure 16. Hysteretic Operation

8.3.1.1 Constant Off-Time vs. Constant µs×V operation

Although commonly referred to as constant off-time, the off-time does vary with the output voltage in the standard

TPS92518 configuration. This relation ensures constant peak-to-peak inductor current ripple (ΔI

L-PP

). Although

not common, the VLEDx pin can be set to a fixed value to generate a truly constant off-time and limit changes in

frequency, however current regulation degrades. To maintain regulation and a constant ripple over various output

voltages, the converter off-time must become shorter or longer as VLEDx pin voltage changes. This results in a

change in frequency. In this regard, the off-time register can be considered as a seconds-times-volts setting (s ×

V) for the converter. The TPS92518 Electrical Characteristics table specification for off-time specifies a certain off

time duration for a certain register value. The time is also dependent on the VLEDx pin voltage. For example, the

off-time is specified at 4 µs for a V

VLEDx

= 30 V and LEDx_TOFF_DAC = 255. The internal analog circuitry

operates to keep the ripple and µs·V (micro-second volt) product constant. If the LEDx voltage changes to 15 V,

the off time adjusts to 8 µs. If the LEDx voltage changes to 60 V the off time adjusts to 2 µs, and so on.

Two general cases can be examined: If the input voltage and output voltage are relatively constant, the

frequency also remains constant. If either the input voltage or the output voltage changes, the frequency

changes. For a fixed input voltage, the device operates at the maximum frequency at 50% duty cycle and the

frequency reduces as the duty cycle becomes shorter or longer. A graphical representation is shown in

Figure 17.

For a fixed output voltage (V

VLEDx

), the off-time stays fixed. The frequency then increases as the duty cycle

becomes smaller with an increasing VIN voltage. This relation is shown in Figure 18.

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