Analog Devices Inc. LT3967JFE#PBF

Overview

LT3967JFE#PBF from Analog Devices is an 8-channel LED bypass switching IC for precision dimming of high-voltage LED strings using a common current source. It integrates eight independent 15V/110mΩ NMOS switches, supports I²C-controlled PWM dimming (100–1000 Hz), provides open/shorted LED fault detection per channel, and operates with VIN up to 60V and junction temperature up to 150°C - used in automotive headlight clusters and RGBW color-mixing lighting.

For engineers reviewing the LT3967JFE#PBF datasheet, LT3967JFE#PBF pinout, LT3967JFE#PBF application, or LT3967JFE#PBF equivalent, key selection considerations include per-channel fade transition control (11-bit exponential), programmable VOTH/VSTH thresholds, watchdog timer with 15–20 ms timeout, thermal shutdown at 170°C, and TSSOP-28 thermally enhanced package with exposed GND pad.

Technical Context

The LT3967JFE#PBF implements a floating-source NMOS matrix architecture where each DRN/SRC pair forms a bypass switch across individual LEDs or segments. Its I²C interface uses address pins ADDR[4:1] to support up to 16 devices on one bus, with register-mapped control of fade time (FTM[2:0]), PWM frequency (via RTSYNC resistor or external clock), and fault reporting (ALERT assertion on open LED, shorted LED, overheat ≥170°C, or RTSYNC clock fault).

Operation requires VIN ≥ SRC + 6V for valid switch biasing; ENH enables/disables functionality via UVLO (1.1–1.34 V hysteresis); VDD powers logic and I²C (2.7–5.5 V); and WDI configures watchdog timeout via external capacitor. The internal oscillator divides by 2048 to generate PWM clock, with fallback to 100 kHz standby mode if input clock drops below 100 kHz.

Key Specifications

Pinout & Package

LT3967JFE#PBF is housed in a 28-lead plastic TSSOP (FE package) with exposed GND pad (Pin 29), θJA = 30°C/W. The thermally enhanced layout requires soldering the exposed pad directly to PCB ground plane for reliable operation at full load and high ambient temperature.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LT3967EFE#PBF, the LT3967JFE#PBF offers extended high-temperature operation critical for engine bay placement, while MAX20051ATG+T trades pin compatibility for integrated power conversion - making LT3967JFE#PBF optimal for modular, high-reliability LED string architectures with external current sources.

Availability

LT3967JFE#PBF is available at Aetrix Electronics and suitable for automotive LED headlight clusters, large LED displays, and RGBW color-mixing lighting requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LT3967JFE#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 semiconductor company specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision instrumentation, industrial automation, and automotive safety systems.

The LT3967 product line was designed specifically for high-reliability LED current-shunting applications in automotive and architectural lighting, emphasizing fault resilience, thermal robustness, and I²C-configurable flexibility over fixed-function alternatives.

FAQ

What is the maximum LED string voltage supported by the LT3967JFE#PBF?

The LT3967JFE#PBF supports LED strings up to 54 V, provided VIN is at least 6 V higher than the channel source voltage (SRC). This constraint ensures valid operation of the floating-source NMOS switches and accurate open/shorted LED fault detection. For example, with SRC = 0 V, VIN must be ≥ 6 V; with SRC = 48 V, VIN must be ≥ 54 V - limiting practical string voltage to ≤54 V in most configurations.

How does the LT3967JFE#PBF handle open LED faults during operation?

When an open LED fault is detected - determined by comparing DRN–SRC voltage against programmable VOTH thresholds - the LT3967JFE#PBF automatically turns on the corresponding channel switch to bypass the faulty LED and maintain string continuity. The ALERT pin is asserted low, and the fault is logged in the read-only LED fault status register. PWM dimming for that channel halts until cleared via I²C command or power cycle.

Can the LT3967JFE#PBF operate without an external microcontroller?

No - the LT3967JFE#PBF requires an I²C master (e.g., MCU or FPGA) for configuration and real-time control. It has no autonomous dimming mode: all channel states (ON/OFF/PWM/fade), fault thresholds, watchdog settings, and PWM frequency must be written via I²C commands. However, power-up defaults (set by ADDR[4:1] resistors) allow basic static operation until initialization.

What is the purpose of the ENH pin on the LT3967JFE#PBF?

The ENH pin serves dual functions: it enables/disables the LT3967JFE#PBF via undervoltage lockout (UVLO) and monitors input supply health. When VIN – ENH falls below ~1.22 V, the device enters shutdown, disabling PWM dimming and fault reporting. ENH is typically connected to a resistor divider from VIN, ensuring activation only when the main supply exceeds a safe threshold - e.g., >6 V above SRC voltage.

Does the LT3967JFE#PBF support synchronized dimming across multiple devices?

Yes - the LT3967JFE#PBF supports synchronized dimming via its RTSYNC pin. When multiple devices share a common external clock signal applied to RTSYNC, their internal PWM generators lock to the same timing reference, eliminating beat frequencies and ensuring frame-aligned dimming transitions across large LED arrays or multi-module systems.