Analog Devices Inc. LTC2925CUF#PBF

Overview

LTC2925CUF#PBF from Analog Devices (formerly Linear Technology) is a multiple power supply tracking and sequencing controller IC designed to coordinate ramp-up/ramp-down of up to four DC/DC supplies in microprocessor, FPGA, and DSP systems. It supports flexible tracking (coincident, offset, ratiometric), adjustable power good timeout (via PGTMR capacitor), electronic circuit breaker protection (50mV sense threshold), and controls three supplies without series FETs while optionally managing a fourth via external N-channel FET gate drive.

For engineers reviewing the LTC2925CUF#PBF datasheet, LTC2925CUF#PBF pinout, LTC2925CUF#PBF application, or LTC2925CUF#PBF equivalent, key selection considerations include its 24-lead QFN (4mm × 4mm) package, 0°C to 70°C operating range, 2.9V–5.5V VCC supply, 0.8V TRACK reference, and integrated remote sense switch (15Ω) for FET voltage-drop compensation.

Technical Context

The LTC2925CUF#PBF implements a wide-range current-mirror-based tracking architecture where each TRACKx pin (TRACK1–TRACK3) is servoed to 0.8V and mirrors current into corresponding FBx pins to force slave supply outputs to track a master signal-either generated by GATE/RAMP capacitor charging or an external FET source. Its ON pin (1.232V threshold, 75mV hysteresis) initiates ramp control with ±10µA sourcing/sinking capability.

It integrates three independent timing functions: SDTMR (shutdown delay), SCTMR (short-circuit timer, 50µA pull-up/2µA pull-down, 1.23V trip), and PGTMR (power good timeout, 10µA pull-up, 1.23V trip). The GATE driver includes a charge pump ensuring ≥5V gate overdrive above VCC, and FAULT/STATUS outputs provide open-drain fault signaling and power-good status indication.

Key Specifications

Pinout & Package

Package: 24-lead (4mm × 4mm) plastic QFN (UF package), exposed pad (Pin 25) - thermally enhanced surface-mount package with 0.5mm lead pitch and optional GND connection for improved thermal performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar power supply tracking and sequencing applications.

Compared with LTC2923CUF#PBF, the LTC2925CUF#PBF adds third-supply tracking, power good timeout, and electronic circuit breaker - essential for robust FPGA/server power management. Versus TPS652860RSLR, it offers greater sequencing flexibility and external FET control but requires more external components.

Availability

LTC2925CUF#PBF is available at Aetrix Electronics and suitable for server motherboard design, FPGA power sequencing, and industrial communications equipment requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for LTC2925CUF#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. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors with deep expertise in precision power control and reliability-critical applications.

The LTC2925CUF#PBF belongs to Linear's PowerPath™ and supply monitoring product line, engineered specifically for high-reliability power sequencing in computing, telecom, and industrial systems where supply coordination, fault tolerance, and timing accuracy are mission-critical.

FAQ

What is the function of the REMOTE pin on the LTC2925CUF#PBF?

The REMOTE pin on the LTC2925CUF#PBF is a 15Ω analog switch that connects the RAMP node to REMOTE only when the GATE pin voltage exceeds RAMP + 4.9V - indicating full FET enhancement. This compensates for voltage drop across the external sense resistor and N-channel FET during regulation, ensuring accurate tracking of the true output voltage rather than the FET source node. In the LTC2925CUF#PBF, this feature enables precise closed-loop correction without additional op-amps or sensing circuitry.

How does the LTC2925CUF#PBF implement power good timeout, and what external component is required?

The LTC2925CUF#PBF implements power good timeout using the PGTMR pin, which sources a 10µA current to charge an external capacitor to 1.23V. If the PGI pin (connected to an external supply monitor's RST output) remains low when this threshold is crossed, the FAULT pin pulls low and GATE is forced to ground. The required component is a capacitor (CPGTMR) tied from PGTMR to GND - its value determines timeout duration per CPGTMR = (10µA × tPGTMR) / 1.23V. This mechanism ensures automatic shutdown if downstream regulation is not confirmed within the programmed window.

Can the LTC2925CUF#PBF control supplies with feedback voltages other than 0.8V?

Yes, the LTC2925CUF#PBF can control slave supplies with feedback voltages ranging from 0V to 1.6V. Its FBx pins inject current into the slave's feedback node to force output tracking, and internal clamping limits FBx voltage to ≤2.5V to prevent damage. While the TRACKx pins are servoed to 0.8V, the actual output voltage is determined by the slave supply's feedback resistor divider ratio - allowing compatibility with common 0.6V, 0.765V, 1.235V, and 1.25V reference ICs. This flexibility makes the LTC2925CUF#PBF usable across diverse DC/DC controller families.

What is the maximum current the TRACKx pins can source in the LTC2925CUF#PBF, and how does it vary with supply voltage?

The TRACKx pins on the LTC2925CUF#PBF can source at least 1mA when VCC = 2.9V, and up to 30mA when VCC = 5.5V - though continuous sourcing above ~3mA is discouraged due to thermal constraints. This wide current range allows driving standard resistor dividers (e.g., 10kΩ–100kΩ) for precise tracking ratios while maintaining stability. The LTC2925CUF#PBF datasheet specifies TRACKx current mismatch ≤±5% across load and temperature, ensuring consistent tracking accuracy among all three channels.

Does the LTC2925CUF#PBF require external components for basic operation, and which ones are mandatory?

Yes, the LTC2925CUF#PBF requires several external components for functional operation: a 0.1µF bypass capacitor on VCC-to-GND is mandatory for stability; at minimum, one capacitor on GATE-to-GND sets ramp rate; and resistive dividers from RAMPBUF to each TRACKx pin define tracking profiles. For optional features: PGTMR, SCTMR, and SDTMR capacitors enable power good timeout, short-circuit protection, and shutdown delay respectively. The LTC2925CUF#PBF operates without external FETs for three-supply control, but adds GATE, RAMP, SENSEP/SENSEN, and REMOTE connections when managing a fourth supply.