Analog Devices Inc. LTC3311JV-0.85#PBF

Overview

LTC3311JV-0.85#PBF from Analog Devices is a monolithic, Silent Switcher® synchronous step-down DC/DC converter delivering up to 12.5A output current from a 2.25V–5.5V input, with fixed 0.85V output voltage, ±1% accuracy (with remote sense), and 35ns minimum on-time. It operates in forced continuous or pulse-skipping mode and is used in FPGA/ASIC core supplies requiring low-noise, high-efficiency POL regulation.

For engineers reviewing the LTC3311JV-0.85#PBF datasheet, LTC3311JV-0.85#PBF pinout, LTC3311JV-0.85#PBF application, or LTC3311JV-0.85#PBF equivalent, key selection criteria include its 0.85V fixed output, 18-lead 3mm × 3mm LQFN package with exposed PGND pad, AEC-Q100 qualification for automotive use, and support for multi-phase paralleling via MODE/SYNC.

Technical Context

The LTC3311JV-0.85#PBF employs constant-frequency peak current mode control with a 500mV internal reference scaled for 0.85V output via internal resistor divider (LTC3311-X variant). Its Silent Switcher 1 architecture minimizes EMI through symmetrical layout and integrated bypass capacitors, enabling CISPR Class 5 compliance without external filters.

It integrates dual power MOSFETs (4.5mΩ NMOS / 16mΩ PMOS), supports clock synchronization up to 5MHz via MODE/SYNC, and features active voltage positioning (2.0mV/A) for improved transient response. Thermal shutdown, output overvoltage protection, and die temperature monitoring via SSTT pin are embedded.

Key Specifications

Pinout & Package

Package: 18-lead 3mm × 3mm LQFN with exposed PGND pad (Pin 19), θJCbottom = 9°C/W, thermally enhanced for high-power density applications.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous step-down converter applications.

Compared with LTC3311HV-0.85#PBF, the LTC3311JV-0.85#PBF offers identical functionality at lower cost for standard automotive and industrial use, while MP2960GQ-Z trades EMI performance and advanced features for lower unit price in less demanding environments.

Availability

LTC3311JV-0.85#PBF is available at Aetrix Electronics and suitable for FPGA core supplies, automotive ADAS processor rails, and industrial PLC CPU core rails requiring stable component supply, AEC-Q100 qualification, and high-current POL regulation.

Supply support for LTC3311JV-0.85#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 precision instrumentation, communications, and industrial markets.

The LTC3311 family is designed for high-efficiency, low-EMI point-of-load conversion in space-constrained systems - specifically targeting FPGA, ASIC, and microprocessor core supplies where thermal density, noise sensitivity, and reliability are critical.

FAQ

What is the output voltage tolerance of the LTC3311JV-0.85#PBF under full load and temperature variation?

The LTC3311JV-0.85#PBF guarantees ±1% output voltage accuracy over –40°C to +150°C junction temperature and full 12.5A load, measured with remote sensing. At 12.5A and 150°C, the regulated output remains within 841.5mV–858.5mV (±1% of 0.85V), as confirmed in the Electrical Characteristics table (Note 5). This includes line, load, and temperature effects - no external calibration is needed.

Can the LTC3311JV-0.85#PBF be synchronized to an external clock, and what is the supported frequency range?

Yes, the LTC3311JV-0.85#PBF supports external clock synchronization via the MODE/SYNC pin. It accepts square-wave inputs from 0.5MHz to 2.25MHz and locks its internal oscillator using an integrated PLL. The device automatically adapts slope compensation and enters forced continuous mode during sync - ensuring stable multi-phase operation without additional timing components. This capability is fully documented in the "Synchronizing the Oscillator to an External Clock" section of the datasheet.

How does the Active Voltage Positioning (AVP) function work in the LTC3311JV-0.85#PBF, and what is its design impact?

The LTC3311JV-0.85#PBF implements AVP with a fixed 2.0mV/A load-line droop. As load current increases, the output voltage decreases linearly - e.g., from 0.855V at 0A to 0.845V at 5A. This intentional droop improves transient response by storing energy in the output capacitor during light loads, reducing peak undershoot during sudden load steps. It directly lowers required output capacitance and eliminates need for external droop networks.

What thermal management guidance applies to the LTC3311JV-0.85#PBF in high-current operation?

For reliable 12.5A operation, the LTC3311JV-0.85#PBF requires the exposed PGND pad (Pin 19) to be soldered to a minimum 400mm² copper area with ≥6 thermal vias (0.3mm diameter) connecting to inner/ground planes. With this layout, θJA is ~42°C/W. At 12.5A and 3.3V input, typical power dissipation is ~0.8W - resulting in ~34°C rise above ambient. Derating is recommended above 85°C ambient to maintain <150°C junction temperature.

Is the LTC3311JV-0.85#PBF pin-compatible with other members of the LTC3311 family, such as the LTC3310S or LTC3311S?

No, the LTC3311JV-0.85#PBF is not pin-compatible with the LTC3310S or LTC3311S. While all share the same 18-lead 3mm × 3mm LQFN footprint, pin functions differ significantly - notably, the LTC3311S uses a different MODE/SYNC implementation and lacks SSTT-based temperature monitoring. The datasheet explicitly states "Pin Compatible with LTC3310/LTC3310S and LTC3311S" only for the base LTC3311 (adjustable version), not for the -X fixed-output variants like LTC3311JV-0.85#PBF.