Texas Instruments TLC5921DAPRG4

Overview

TLC5921DAPRG4 from Texas Instruments is a 16-channel constant-current LED sink driver with integrated shift register, latch, thermal shutdown (TSD), and LED open detection (LOD). It delivers up to 80 mA per channel with ±4% max current matching, supports 20 MHz serial data transfer, operates from 4.5 V to 5.5 V, and targets high-density LED signage and industrial panel displays.

For engineers reviewing the TLC5921DAPRG4 datasheet, TLC5921DAPRG4 pinout, TLC5921DAPRG4 application, or TLC5921DAPRG4 equivalent, key selection criteria include its 16-bit serial-in/serial-out daisy-chain capability, IREF-based current programming, open-collector XDOWN fault reporting, and HTSSOP-32 PowerPAD thermal package for sustained 80 mA/channel operation.

Technical Context

The TLC5921DAPRG4 integrates a 16-bit shift register and parallel latch to control 16 independent constant-current sinks. Data is clocked in synchronously via SIN/SCLK, latched on XLAT, and output timing on SOUT is selectable via SOMODE (rising- or falling-edge synchronized).

Each output channel sinks up to 80 mA with current set by a single external resistor at IREF (38× reference current). LOD monitors each OUTn voltage during ON-state; if <0.3 V, XDOWN asserts low. TSD disables all outputs when junction temperature exceeds 150–170°C.

Key Specifications

Pinout & Package

Package: 32-pin HTSSOP (DAP) with exposed thermal pad (PowerPAD™); 8.1 mm × 11.0 mm footprint, 1.2 mm max height, 0.65 mm pitch. Thermal pad must be soldered to PCB ground plane for thermal management and noise reduction.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLC5922DAPR and MAX7219CWG+, the TLC5921DAPRG4 provides the most cost-effective solution for fixed-intensity, high-channel-count LED arrays where integrated LOD and TSD are mandatory, while avoiding unnecessary complexity from PWM or display-specific features.

Availability

TLC5921DAPRG4 is available at Aetrix Electronics and suitable for architectural signage, industrial HMI panels, and automated test equipment requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for TLC5921DAPRG4 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 technologies, with decades of experience in high-reliability industrial and automotive solutions.

The TLC5921DAPRG4 belongs to TI's legacy LED driver product line designed specifically for high-channel-count, constant-current LED array control in industrial and commercial signage applications where thermal resilience and fault visibility are critical.

FAQ

What is the maximum continuous current per channel for the TLC5921DAPRG4?

The TLC5921DAPRG4 supports up to 80 mA per output channel (OUT0–OUT15) under recommended operating conditions (VCC = 4.5–5.5 V, TA ≤ 85°C, proper thermal pad soldering). Absolute maximum rating is 90 mA, but sustained operation above 80 mA risks exceeding thermal limits and triggering TSD. The actual current is set by the external IREF resistor and remains stable across all 16 channels within ±4% max mismatch.

How does the LED open detection (LOD) function work on the TLC5921DAPRG4?

The TLC5921DAPRG4 performs LOD by monitoring each OUTn voltage during active ON-state. If the voltage drops below ~0.3 V while the corresponding latch bit is high, the device interprets this as an open LED and pulls XDOWN low. To identify which channel failed, the system must sequentially enable one OUTn at a time and check XDOWN - a low state during that specific enable confirms the disconnected LED. BLANK must be low for LOD to operate.

Can the TLC5921DAPRG4 be used in daisy-chain configuration, and what are the timing constraints?

Yes, the TLC5921DAPRG4 supports daisy-chaining via SIN → SOUT connections between devices. In cascade mode with SOMODE = L, the maximum SCLK frequency is reduced to 15 MHz (vs. 20 MHz in single-device mode) to ensure reliable inter-device data propagation. Setup/hold times remain identical (t_su = 5 ns, t_h = 20 ns), and XLAT must be asserted simultaneously across all chained devices to update outputs coherently.

What is the role of the thermal pad on the TLC5921DAPRG4 HTSSOP package?

The exposed thermal pad on the TLC5921DAPRG4's HTSSOP-32 package serves two critical functions: it provides a low-thermal-resistance path to dissipate up to 3.9 W (at TA = 25°C), and it acts as a noise-reduction ground plane when soldered to the PCB's GND layer. TI specifies that the pad must be connected to GND - not left floating - to ensure both thermal stability and EMI suppression, especially during high-current switching of all 16 channels.

How is output current programmed on the TLC5921DAPRG4, and what resistor value yields 60 mA per channel?

Output current is set by connecting a resistor R_IREF between IREF (Pin 31) and GND. The relationship is I_OUT = 38 × I_IREF, where I_IREF = V_REF/R_IREF and V_REF ≈ 1.3 V. For 60 mA per channel: R_IREF = (38 × 1.3 V) / 60 mA ≈ 828 Ω. A standard 820 Ω resistor yields ~60.5 mA (within datasheet tolerance). Layout best practice: place R_IREF as close as possible to Pin 31 to minimize noise coupling.