TLC5916, TLC5917

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SLVS695D – JUNE 2007 – REVISED JANUARY 2015

9 Detailed Description

9.1 Overview

The TLC591x is designed for LED displays and LED lighting applications with constant-current control and open-

load, shorted-load, and overtemperature detection. The TLC591x contains an 8-bit shift register and data latches,

which convert serial input data into parallel output format. At the output stage, eight regulated current ports are

designed to provide uniform and constant current for driving LEDs within a wide range of LED Forward Voltage

(VF) variations. Used in system design for LED display applications, for example, LED panels, it provides great

flexibility and device performance. Users can adjust the output current from 3 mA to 120 mA per channel through

an external resistor, Rext, which gives flexibility in controlling the light intensity of LEDs. The devices are designed

for up to 20 V at the output port. The high clock frequency, 30 MHz, also satisfies the system requirements of

high-volume data transmission.

The TLC591x provides two operation modes: Normal Mode and Special Mode. Normal mode is used for shifting

LED data into and out of the driver. Special Mode includes two functions: Error Detection and Current Gain

Control. The two operation modes include three phases: Normal Mode phase, Mode Switching transition phase,

and Special Mode phase. The signal on the multiple function pin OE(ED2) is monitored to determine the mode.

When a one-clock-wide pulse appears on OE(ED2), the device enters the Mode Switching phase. At this time,

the voltage level on LE(ED1) determines which mode the TLC591x switches to.

In the Normal Mode phase, the serial data can be transferred into TLC591x through the pin SDI, shifted in the

shift register, and transferred out via the pin SDO. LE(ED1) can latch the serial data in the shift register to the

output latch. OE(ED2) enables the output drivers to sink current.

In the Special Mode phase, the low-voltage-level signal on OE(ED2) can enable output channels and detect the

status of the output current to determine if the driving current level is sufficient. The detected Error Status is

loaded into the 8-bit shift register and shifted out via the pin SDO, synchronous to the CLK signal. The system

controller can read the error status and determine if the LEDs are properly lit.

In the Special Mode phase, the TLC591x allows users to adjust the output current level by setting a runtime-

programmable Configuration Code. The code is sent into the TLC591x through SDI. The positive pulse of

LE(ED1) latches the code in the shift register into a built-in 8-bit configuration latch, instead of the output latch.

The code affects the voltage at the terminal R-EXT and controls the output-current regulator. The output current

can be finely adjusted by a gain ranging from 1/12 to 127/128 in 256 steps. Therefore, the current skew between

ICs can be compensated within less than 1%. This feature is suitable for white balancing in LED color display

panels.

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Product Folder Links: TLC5916 TLC5917