Microchip Technology MSL3085BT

Overview

MSL3085BT from Microchip Technology (formerly Atmel) is an 8-string white/RGB LED driver IC using external MOSFETs to sink up to 350mA per string with ±1.5% current accuracy and matching, integrated EEPROM, I²C/SMBus interface, and adaptive DC-DC power control for LCD TV and medical display backlighting.

For engineers reviewing the MSL3085BT datasheet, MSL3085BT pinout, MSL3085BT application, or MSL3085BT equivalent, this device supports frame-synchronized area dimming, 12-bit per-string PWM, video timing sync (PHI/GSC), fault-aware open/short detection, and multi-device chain negotiation of optimal LED supply voltage - critical for high-dynamic-range backlight systems.

Technical Context

The MSL3085BT implements a programmable PWM engine synchronized to external video signals via PHI (frame sync) and GSC (line sync), enabling phase-shifted string drive to reduce motion blur and input capacitor stress. Its dual efficiency optimizer outputs (FBO1/FBO2) dynamically adjust external DC-DC supplies by injecting 0–360µA feedback current, with FBI1 input supporting daisy-chained optimization across up to eight devices.

It uses external N-channel MOSFETs (gate charge ≤10nC) for high-current sinking, with source-sense inputs (S0–S14) regulating string current at 500mV threshold and drain-sense inputs (D0–D14) detecting open/short faults. The 1MHz I²C interface supports broadcast writes and up to eight devices on one bus, with register compatibility maintained with the MSL2161 family despite non-sequential pin naming (strings 0, 2, 4, 6, 9, 11, 12, 14).

Key Specifications

Pinout & Package

MSL3085BT is housed in a 40-pin, 6 mm × 6 mm × 0.75 mm TQFN package with exposed thermal pad (EP). Pin layout supports dual efficiency optimizer chaining (FBO1/FBI1), video synchronization (PHI/GSC), fault reporting (FLTB), and 8-channel MOSFET gate/source/drain sensing with non-sequential numbering (strings 0, 2, 4, 6, 9, 11, 12, 14) for register compatibility with MSL2161.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-channel LED driver applications.

Compared with TLC6983RGER and NCP5623DR2G, the MSL3085BT uniquely combines high-current external-FET drive (350mA), video-synchronized PWM phasing, adaptive supply negotiation, and industrial temperature range - making it the sole option for demanding LCD TV, medical, and automotive local dimming applications.

Availability

MSL3085BT is available at Aetrix Electronics and suitable for television backlighting, medical imaging displays, and automotive infotainment systems requiring stable component supply, long-lifecycle support, and guaranteed traceability.

Supply support for MSL3085BT 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

Microchip Technology acquired Atmel in 2016 and maintains its high-performance analog and mixed-signal product lines, including LED drivers, with focus on automotive, industrial, and computing markets.

The MSL3085BT belongs to Microchip's Adaptive LED Driver product line, engineered specifically for high-efficiency, video-synchronized local dimming in LCD backlight systems where dynamic contrast, thermal resilience, and multi-device scalability are critical.

FAQ

What is the maximum LED string current supported by the MSL3085BT?

The MSL3085BT supports up to 350mA per LED string, set by an external current-sense resistor connected to each source-sense pin (e.g., S0, S2). The internal regulation threshold is fixed at 500mV, so RS = 5.0 / ILED (in ohms for amperes). This value is confirmed in the Electrical Characteristics table under "S0 thru S7 regulation voltage" and "S0 thru S7 voltage matching" specifications. The MSL3085BT maintains ±1.5% current accuracy across all eight strings under full load and temperature range.

Does the MSL3085BT require external MOSFETs, and what are their gate drive requirements?

Yes, the MSL3085BT requires external N-channel MOSFETs for LED string sinking. Its gate drive outputs (G0, G2, etc.) are optimized for FETs requiring ≤10nC total gate charge, as stated in the "MSL3085 Overview" section. The device does not integrate power switches. Gate drive voltage is derived from VDD (2.5V) and VCC (5V) internal regulators, and no external level shifters are needed. This architecture allows flexible selection of high-voltage or high-current FETs beyond integrated-driver limitations.

How does the MSL3085BT synchronize with video timing signals like VSYNC and HSYNC?

The MSL3085BT uses two dedicated inputs: PHI accepts frame-sync signals (0.04–10 kHz, typically VSYNC) to align PWM frame boundaries, while GSC accepts line-sync signals (0–10 MHz, typically HSYNC) to control pixel-level PWM phasing. The internal PWM engine multiplies PHI frequency (1× to 32×) and counts GSC cycles to achieve 12-bit on-time resolution. This synchronization reduces motion blur and waterfall artifacts in LCD TVs and monitors, as detailed in the "Timing, PWM, Intensity Controls and Synchronization" section.

Can multiple MSL3085BT devices share a single LED power supply, and how is voltage negotiation handled?

Yes, multiple MSL3085BT devices can share one or two LED power supplies using the FBO1/FBI1 daisy-chain interface. When chained, devices automatically negotiate the minimum supply voltage required to maintain current regulation across all strings - preventing overvoltage and excess power dissipation. Each FBO1 injects up to 360µA into the supply's feedback node; FBI1 accepts upstream FBO1 output. Accuracy degrades by ≤2% per link, limiting practical chains to ≤8 devices, as specified in the "Using Multiple MSL3085BTs" application note.

What fault conditions does the MSL3085BT detect, and how are they reported?

The MSL3085BT detects LED string open-circuit (via D0–D14 ≥8V), short-circuit (via S0–S14 voltage deviation), loss-of-PHI/GSC sync, and over-temperature. Faults trigger the open-drain FLTB pin (active-low) and populate status bits in I²C-accessible fault registers (0x00–0x02). Individual string fault detection can be enabled/disabled per string via configuration registers. FLTB remains asserted until fault registers are read, ensuring no transient faults are missed by the host MCU - a requirement verified in the "Fault Detection and Management" subsection.