Texas Instruments TLC5940RHB

Overview

TLC5940RHB from Texas Instruments is a 16-channel constant-current sink LED driver with 12-bit (4096-step) grayscale PWM control, 6-bit (64-step) dot correction stored in integrated EEPROM, and thermal/LED-open error detection. Each channel delivers up to 120 mA (VCC > 3.6 V) with ±4% current matching across channels, supporting high-precision LED display brightness uniformity in signage and backlighting systems.

For engineers reviewing the TLC5940RHB datasheet, TLC5940RHB pinout, TLC5940RHB application, or TLC5940RHB equivalent, key selection considerations include its 32-pin VQFN package with thermal pad, 30 MHz serial interface speed, 17 V LED supply capability, and dual-error flag reporting via open-drain XERR output.

Technical Context

The TLC5940RHB implements two independent serial data paths: 96-bit grayscale (GS) data for PWM timing and 192-bit dot correction (DC) data for per-channel current trimming, both loaded via SIN/SCLK/XLAT with MSB-first protocol. GSCLK drives a 12-bit counter per channel, while DC data adjusts sink current in 64 discrete steps using internal DACs referenced to IREF.

Error handling is hardware-automated: LED open detection (LOD) triggers when OUTn voltage falls below 0.3 V during active drive, and thermal error flag (TEF) activates at 150–170 °C junction temperature. Both assert low on shared open-drain XERR, with LOD maskable via BLANK = HIGH.

Key Specifications

Pinout & Package

Package: 32-pin VQFN (5.0 mm × 5.0 mm, 0.5 mm pitch) with exposed thermal pad (RHB suffix). Thermal pad must be soldered to PCB ground plane for rated 34.3 °C/W θJA performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar LED driver applications.

Compared with TLC5941RHB and MAX6966AUG+, the TLC5940RHB uniquely balances 4096-step grayscale, EEPROM-stored dot correction, and dual hardware error flags in a 32-pin VQFN-making it optimal for cost-sensitive, reliability-critical LED signage where diagnostics reduce field service calls.

Availability

TLC5940RHB is available at Aetrix Electronics and suitable for LED signage, full-color video walls, automotive interior lighting, and industrial HMI backlighting requiring stable component supply and long-term production continuity.

Supply support for TLC5940RHB includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and power management ICs, with decades of expertise in precision LED control and industrial-grade reliability.

The TLC5940RHB belongs to TI's high-accuracy LED driver product line, designed specifically for applications demanding consistent brightness, per-channel current trimming, and robust fault detection in commercial and industrial displays.

FAQ

What is the maximum LED supply voltage supported by the TLC5940RHB?

The TLC5940RHB supports an LED supply voltage up to 17 V on its OUT0–OUT15 pins. This allows direct driving of multi-LED series strings without external boost converters, simplifying power architecture in signage and backlighting designs. The 17 V rating is absolute maximum; operation above 15 V requires careful thermal management due to increased power dissipation in the output transistors.

How does the TLC5940RHB implement dot correction, and where is the data stored?

The TLC5940RHB implements 6-bit (64-step) dot correction per channel using internal DACs referenced to the IREF pin. Correction values adjust the sink current magnitude independently for each of the 16 outputs to compensate for LED forward-voltage variation and PCB trace resistance mismatches. All 16 × 6-bit values are stored in an integrated EEPROM, retaining calibration across power cycles without external memory.

Can multiple TLC5940RHB devices be cascaded, and what is required for daisy-chaining?

Yes, multiple TLC5940RHB devices can be cascaded using the SOUT-to-SIN connection. Each device shifts its 192-bit data (16 × 6-bit DC + 16 × 12-bit GS) into the next. The master controller sends one continuous stream: first 192 bits to the last device, then next 192 to the prior, etc. XLAT must be asserted after full data load to latch all stages simultaneously. No additional control lines are needed beyond shared SCLK, XLAT, and BLANK.

What conditions trigger the XERR output on the TLC5940RHB, and how are they differentiated?

The XERR output on the TLC5940RHB goes LOW for either LED open detection (LOD) or thermal error flag (TEF) assertion. LOD triggers when any OUTn voltage drops below 0.3 V while actively sinking current; TEF triggers at 150–170 °C junction temperature. LOD can be masked by holding BLANK = HIGH; TEF remains active regardless. Status bits for both errors are also readable via SOUT after XLAT pulse, enabling software differentiation.

What is the role of the IREF pin, and how is output current calculated for the TLC5940RHB?

The IREF pin sets the full-scale output current for all 16 channels via an external resistor. The relationship is IOUT(max) = 31.5 × V(IREF)/R(IREF), where V(IREF) is nominally 1.24 V. For example, a 1.24 kΩ resistor yields ~31.5 mA per channel (VCC > 3.6 V). Current accuracy depends on R(IREF) tolerance and V(IREF) drift; TI specifies ±4% channel-to-channel matching under nominal conditions.