Analog Devices Inc. LT3965IFE#PBF

Overview

LT3965IFE#PBF from Analog Devices is an 8-channel I²C-controlled LED bypass switch IC for precision dimming of individual LEDs in high-voltage strings using a common current source. It integrates eight floating-source 17V/330mΩ NMOS switches, supports 256:1 digital PWM dimming with optional logarithmic fade, and reports open/shorted LED faults per channel. It operates with VIN up to 60V and VDD from 2.7V to 5.5V, targeting automotive LED headlight clusters and large-format displays.

For engineers reviewing the LT3965IFE#PBF datasheet, LT3965IFE#PBF pinout, LT3965IFE#PBF application, or LT3965IFE#PBF equivalent, key selection considerations include per-channel fault detection thresholds (programmable VOTH/VSTH), I²C multidrop support via four address pins, internal/external PWM clocking (RTCLK), flicker-free dimming architecture, and AEC-Q100 qualification for automotive use.

Technical Context

The LT3965IFE#PBF implements an 8-channel independent switching matrix where each DRN–SRC pair forms a floating-source NMOS bypass path across one or more LEDs. Switch control, fault detection, and PWM timing are fully managed by on-chip logic synchronized to either an internal resistor-programmed oscillator (via RTCLK) or an external clock source - both divided by 2048 for final dimming frequency.

Fault detection is per-channel and configurable: open-LED threshold (VOTH) offers four settings (4.5V–18V); shorted-LED threshold (VSTH) scales with LEDREF voltage (0–4V input) and supports four programmable levels (e.g., 1V, VLEDREF+1V, etc.). ALERT output asserts low on any detected fault, supporting multi-device bus arbitration via I²C Alert Response Address (ARA).

Key Specifications

Pinout & Package

LT3965IFE#PBF is housed in a 28-lead plastic TSSOP package (FE) with exposed pad (Pin 29) soldered to PCB ground for thermal and electrical integrity. θJC = 10°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LT3965EFE#PBF, the LT3965IFE#PBF guarantees full –40°C operation and AEC-Q100 compliance for automotive deployment; compared with MAX20051ATP/V+T, it delivers higher channel count, true floating-source bypass architecture, and superior fault diagnostics - but requires an external LED driver.

Availability

LT3965IFE#PBF is available at Aetrix Electronics and suitable for automotive LED headlight clusters, large LED displays, automated camera flash equipment, and RGBW color mixing lighting requiring stable component supply, AEC-Q100 compliance, and long-term production continuity.

Supply support for LT3965IFE#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 LT3965IFE#PBF belongs to Analog Devices' Power by Linear™ LED driver and controller family, engineered specifically for high-reliability, high-voltage LED array management in safety-critical automotive and demanding industrial lighting systems.

FAQ

What is the default power-on state of the LT3965IFE#PBF?

The LT3965IFE#PBF initializes all eight NMOS switches in the OFF state (LEDs illuminated) after power-on reset. This behavior distinguishes it from the LT3965-1 variant, which defaults to all switches ON (LEDs off). The default open-LED threshold (VOTH) is set to 18V, and the I²C address defaults to 0x5F (ADDR[4:1] = 1111). These values are loaded automatically unless overridden by prior register writes.

How does the LT3965IFE#PBF detect and respond to an open LED fault?

When the voltage between DRN and SRC of any channel exceeds the programmed VOTH threshold (e.g., 18V default), the LT3965IFE#PBF triggers an open-LED fault. It then asserts the ALERT pin low and turns ON the corresponding NMOS switch to bypass the faulty LED, preserving string continuity. The fault status remains latched in the OLFREG register until cleared via I²C write command or power cycle.

Can the LT3965IFE#PBF drive LEDs directly, or does it require an external LED driver?

The LT3965IFE#PBF is not an LED driver - it is a bypass switch IC and requires an external constant-current LED driver (e.g., LT3955, LT3762, or similar buck/boost LED controller). Its eight NMOS channels shunt current around selected LEDs in a string powered by that driver, enabling per-segment dimming without altering the main current source.

What is the purpose of the LEDREF pin on the LT3965IFE#PBF?

The LEDREF pin sets the reference voltage used to calculate the shorted-LED detection threshold (VSTH). When LEDREF = 0V, VSTH defaults to 1V; when LEDREF = 3V, VSTH becomes programmable across four levels (e.g., 1V, 4V, 7V, 10V). This allows precise adaptation to different LED forward voltages in multi-color or mixed-bin arrays without hardware changes.

Does the LT3965IFE#PBF support synchronization of PWM dimming across multiple devices?

Yes - the LT3965IFE#PBF supports synchronized dimming via its RTCLK pin. By connecting a single external clock source to the RTCLK pins of multiple LT3965IFE#PBF devices, all units derive their PWM timing from the same master clock, eliminating beat frequencies and ensuring coherent dimming across large LED arrays or multi-zone lighting systems.