Analog Devices Inc. LT8603IUJ#PBF

Overview

LT8603IUJ#PBF from Analog Devices is a quad-output power management IC integrating two 42V synchronous buck regulators (Ch1/Ch2), one 5.5V low-input buck regulator (Ch3), and a boost controller (Ch4), delivering up to four precisely regulated outputs with cold-crank tolerance down to 2V input. It supports automotive stop-start, last-gasp CPU hold-up, and industrial control systems with AEC-Q100 qualification (I-grade, –40°C to 125°C).

For engineers reviewing the LT8603IUJ#PBF datasheet, LT8603IUJ#PBF pinout, LT8603IUJ#PBF application, or LT8603IUJ#PBF equivalent, key selection considerations include its 28µA quiescent current in Burst Mode®, 250kHz–2.2MHz programmable switching frequency, individual channel power-good indicators (PG1–PG4), and robust –42V reverse-battery tolerant boost controller.

Technical Context

The LT8603IUJ#PBF implements independent control loops for each of its four channels: Ch1 and Ch2 use cycle-by-cycle current limiting with 2.7A and 4.0A peak switch current limits respectively; Ch3 employs a low-voltage synchronous buck architecture with 3.2A peak limit and 150mΩ/100mΩ PMOS/NMOS R_DS(ON); Ch4 functions as a high-side gate driver-based boost controller with 50mV current-sense threshold and ±42V input tolerance.

Its architecture enables flexible system-level configurations - including boost-supplied VIN for cold-crank operation (VBATT << VOUT), SEPIC mode, or output-driven enable sequencing - while maintaining precise regulation across all outputs via dedicated FB pins (FB1–FB4) and individual soft-start/track inputs (TRKSS1–2, RUN3, CPOR, POREN).

Key Specifications

Pinout & Package

LT8603IUJ#PBF is housed in a 40-lead plastic QFN package (6mm × 6mm) with an exposed thermal pad (Pin 41). All ground pins (Pins 2, 8, 13, 35, 38, and exposed pad) must be soldered to PCB ground for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad-output automotive power management applications.

Compared with LT8602IUJ#PBF and MAX20090ATPA/VY+, the LT8603IUJ#PBF uniquely combines cold-crank resilience, external boost MOSFET control, and independent low-VIN buck regulation - making it the only option among the three that supports true four-rail, fault-tolerant automotive power architectures.

Availability

LT8603IUJ#PBF is available at Aetrix Electronics and suitable for automotive infotainment, ADAS camera ECUs, and industrial PLC I/O modules requiring stable component supply with AEC-Q100 compliance and long-term production support.

Supply support for LT8603IUJ#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 is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving automotive, industrial, communications, and healthcare markets with precision, reliability, and innovation.

The LT8603IUJ#PBF belongs to Analog Devices' Power by Linear™ family of high-efficiency, high-reliability DC/DC regulators designed specifically for demanding automotive and industrial environments where cold-crank survival, low quiescent current, and multi-rail flexibility are essential.

FAQ

What is the minimum input voltage the LT8603IUJ#PBF can regulate from during automotive cold crank?

The LT8603IUJ#PBF maintains regulation on its three buck outputs (Ch1–Ch3) down to a 2V input on the boost controller's ISP4/ISN4 sense inputs - verified in cold-crank waveforms where VBATT drops to 2V while VOUT4 remains stable at 8V, sustaining the chip's internal supplies. This capability is enabled by the integrated boost controller and is explicitly characterized in the datasheet's "Response to a Cold Crank" plot (TA01a/b).

Does the LT8603IUJ#PBF support synchronization to an external clock?

Yes, the LT8603IUJ#PBF supports external clock synchronization via the SYNC pin (Pin 33). When an external clock signal between 0.25MHz and 2.2MHz is applied, the device synchronizes its internal oscillator and operates in pulse-skipping mode. If synchronization is not required, SYNC should be tied to ground for Burst Mode® operation or pulled high for pulse-skipping - all modes are fully supported in the LT8603IUJ#PBF.

How is power-good signaling implemented on the LT8603IUJ#PBF?

The LT8603IUJ#PBF provides four independent open-drain power-good outputs: PG1 (Pin 1), PG2 (Pin 10), PG3 (Pin 40), and PG4 (Pin 11). Each asserts low until its corresponding feedback voltage (FB1–FB4) reaches 92% of the target reference (1.0V for Ch1/Ch2, 0.8V for Ch3/Ch4), with 8% hysteresis. These outputs require external pull-up resistors and directly interface with processor reset controllers or FPGA configuration managers.

Can the LT8603IUJ#PBF operate without the BIAS pin connected?

Yes, the LT8603IUJ#PBF operates without BIAS connected - the INTVCC and INTVCC4 regulators will draw power from VIN and PVIN1/PVIN2 respectively. However, connecting BIAS > 3.1V reduces VIN quiescent current by powering INTVCC from BIAS, and BIAS > 4.6V similarly powers INTVCC4, lowering on-chip dissipation and improving light-load efficiency. The BIAS pin is optional but recommended for thermally constrained or ultra-low-I_Q designs.

What is the purpose of the TRKSS1 and TRKSS2 pins on the LT8603IUJ#PBF?

TRKSS1 (Pin 21) and TRKSS2 (Pin 20) serve dual roles on the LT8603IUJ#PBF: they act as track inputs to force Ch1/Ch2 outputs to follow an external voltage ramp during startup, and as soft-start inputs when a capacitor is connected to ground - setting the output voltage ramp time. Each pin has a 2.4µA internal pull-up, enabling simple RC soft-start programming (e.g., 100nF yields ~1ms ramp) and precise rail sequencing in multi-voltage systems.