Analog Devices Inc. LT8500ITJ#PBF

Overview

LT8500ITJ#PBF from Analog Devices is a 48-channel, 12-bit PWM generator IC designed for high-precision LED backlighting and display control. It delivers independent 4096-step PWM outputs with ±50% per-channel correction, 50MHz cascadable serial interface, and phase-shifted 16-channel bank operation to reduce EMI-used in large-screen LCD backlights and full-color LED signage.

For engineers reviewing the LT8500ITJ#PBF datasheet, LT8500ITJ#PBF pinout, LT8500ITJ#PBF application, or LT8500ITJ#PBF equivalent, key selection considerations include its 56-pin TLA QFN package, –40°C to 125°C industrial temperature grade, diagnostic OPENLED/SYNC error flags, and direct compatibility with three LT3595A LED drivers.

Technical Context

The LT8500ITJ#PBF implements a fully synchronous, cascadable 5-wire serial interface (SDI/SCKI/LDIBLANK/SDO/SCKO) with internal skew balancing and 50MHz SCKI timing. Its 584-bit shift register supports command frames (576-bit data + 8-bit CMD) and status readback including open-LED fault bits and synchronization status.

Each of the 48 PWM channels uses a free-running 12-bit PWMCK counter (up to 25MHz) compared against independently loaded PWMRSYNC registers; correction is applied via a 6-bit multiplier before latching, enabling per-channel gain adjustment from –50% to +50% relative to nominal duty cycle.

Key Specifications

Pinout & Package

LT8500ITJ#PBF is housed in a 56-lead plastic TLA QFN (6mm × 6mm × 0.78mm) with exposed thermal pad (Pin 57 = GND). The package supports high-density PCB layouts and efficient thermal dissipation in LED driver modules.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PWM generator applications.

Compared with LT8500ETJ#PBF, the LT8500ITJ#PBF guarantees full specification compliance over –40°C startup and operation-critical for outdoor signage and automotive infotainment. Versus TLC5947IPWR, it provides double the channel count, diagnostic intelligence, and scalable architecture for large-area LED systems.

Availability

LT8500ITJ#PBF is available at Aetrix Electronics and suitable for large-screen LCD backlighting, full-color LED signage, industrial HMI displays, and automated test equipment requiring stable component supply across extended temperature ranges.

Supply support for LT8500ITJ#PBF 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

Analog Devices, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.

The LT8500 product line was engineered specifically for high-channel-count, high-resolution LED modulation in demanding visual systems-emphasizing timing precision, diagnostic reliability, and scalable interconnect architecture.

FAQ

What is the maximum PWM frequency supported by the LT8500ITJ#PBF?

The LT8500ITJ#PBF supports a maximum PWM clock (PWMCK) frequency of 25MHz. With its 12-bit counter (4096 steps), this yields a maximum PWM output frequency of 6.1kHz. This value is confirmed in the Timing Characteristics table of the official datasheet under fPWMCK and derived PWM period calculations.

Does the LT8500ITJ#PBF require external components for basic operation?

Yes-the LT8500ITJ#PBF requires a local 0.1µF bypass capacitor on the VCC pin to GND, and the exposed thermal pad (Pin 57) must be soldered to a PCB ground plane. No external resistors or timing components are needed for core PWM or serial interface functionality, as OPENLED includes an internal 100kΩ pull-up.

How does the LT8500ITJ#PBF handle open-LED fault detection?

The LT8500ITJ#PBF monitors the OPENLED pin-typically wired to the open-collector outputs of LT3595A drivers-and reports fault status in every status frame. It also supports a diagnostic self-test mode (CMD = 0x5X) that sequentially activates each PWM channel to isolate which specific LED string has failed.

Can multiple LT8500ITJ#PBF devices be cascaded, and what is the maximum chain length?

Yes-LT8500ITJ#PBF supports daisy-chaining via its 5-wire interface (SCKO/SDO routed to next device's SCKI/SDI). Maximum chain length depends on SCKI frequency and layout: at 50MHz, proper skew-balanced routing enables >10 devices; at lower speeds (e.g., 25MHz), >20 devices are achievable without buffers.

What is the function of the LDIBLANK pin on the LT8500ITJ#PBF?

The LDIBLANK pin on the LT8500ITJ#PBF serves two roles: (1) as LDI (Latch Data In), where a rising edge terminates a 584-bit command frame and executes its instruction; and (2) as BLANK, where a >50µs high pulse disables all 48 PWM outputs and resets internal registers-used for emergency shutdown or initialization.