Analog Devices Inc. LTC1735IGN-1#PBF

Overview

LTC1735IGN-1#PBF from Analog Devices (formerly Linear Technology) is a synchronous step-down switching regulator controller optimized for CPU core power delivery in mobile computing systems. It delivers 0.8V–7V output from 3.5V–30V input, supports up to 500kHz synchronization, achieves ±1% output voltage accuracy, and features OPTI-LOOP™ compensation for stable transient response across wide output capacitance/ESR ranges - deployed in SpeedStep-enabled Pentium III notebook DC/DC converters.

For engineers reviewing the LTC1735IGN-1#PBF datasheet, LTC1735IGN-1#PBF pinout, LTC1735IGN-1#PBF application, or LTC1735IGN-1#PBF equivalent, key selection criteria include programmable current limit via RSENSE, 99% dropout duty cycle, PGOOD window comparator (±7.5%), Burst Mode™ efficiency at light load, and dual N-channel MOSFET gate drive capability with BOOST/TG/BG pins.

Technical Context

The LTC1735IGN-1#PBF implements a constant-frequency, current-mode control architecture with peak-current sensing via SENSE+ and SENSE− inputs. Its error amplifier (EA) drives ITH to regulate peak inductor current, while OPTI-LOOP™ compensation adapts loop gain dynamically based on output capacitor ESR and capacitance.

It integrates UVLO (3.5V), internal foldback current limiting (triggered below 70% VOUT), overvoltage crowbar protection (VOVL = 0.84–0.88V), latched short-circuit shutdown with RUN/SS-based timeout, and logic-controlled micropower shutdown (IQ < 25µA). The oscillator frequency is set by COSC (47pF typical) and synchronizable up to 500kHz via PGOOD pin.

Key Specifications

Pinout & Package

Package: 16-lead narrow SSOP (GN), 5.0mm × 6.2mm body, 0.635mm pitch, exposed pad not electrically connected.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous buck controller applications.

Compared with TPS54620RGYR and ISL95836IRZ, the LTC1735IGN-1#PBF offers unmatched flexibility in loop compensation and current limit programming for non-standard output capacitors or custom load profiles, while maintaining proven reliability in legacy mobile CPU designs.

Availability

LTC1735IGN-1#PBF is available at Aetrix Electronics and suitable for notebook computer power systems, mobile processor VRMs, wireless baseband supplies, and industrial FPGA core rails requiring stable component supply with long-term lifecycle support.

Supply support for LTC1735IGN-1#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 acquired Linear Technology in 2017; Linear pioneered high-performance analog ICs for power management, precision signal conditioning, and timing.

The LTC1735IGN-1#PBF belongs to Linear's CPU power controller family, designed specifically for high-efficiency, dynamically scalable core voltage regulation in mobile computing platforms with stringent transient and sequencing requirements.

FAQ

What is the maximum input voltage rating for the LTC1735IGN-1#PBF?

The LTC1735IGN-1#PBF has an absolute maximum input voltage rating of 36V on the VIN pin. Continuous operation is specified from 3.5V to 30V. Exceeding 36V risks permanent damage to internal circuitry, including the INTVCC LDO and gate drivers. Designers must ensure transient spikes (e.g., load dump) remain below this limit using appropriate input clamping or filtering.

How does the LTC1735IGN-1#PBF achieve ±1% output voltage accuracy?

The LTC1735IGN-1#PBF achieves ±1% output voltage accuracy through a precision 0.8V internal reference (±0.5% over temperature), low-drift error amplifier, and tightly controlled feedback path. VOSENSE pin bias current is only –4 to –25nA, minimizing divider resistor-induced errors. This accuracy is guaranteed over the full operating temperature range for the I-grade version (–40°C to +85°C).

Can the LTC1735IGN-1#PBF be synchronized to an external clock, and what are the limits?

Yes, the LTC1735IGN-1#PBF can be synchronized to an external clock applied to the PGOOD pin. The internal oscillator locks to frequencies between 90% and 130% of its nominal COSC-set frequency (e.g., 270–390kHz for 300kHz nominal). Clock high must exceed 1.3V for ≥0.3µs; low must be <0.3V for ≥0.3µs. Attempting sync beyond 130% may cause instability due to insufficient slope compensation.

What protection features does the LTC1735IGN-1#PBF include for short-circuit conditions?

The LTC1735IGN-1#PBF includes foldback current limiting (active when VOSENSE drops below 0.6V), output overvoltage crowbar (trips at 0.84–0.88V), and latched short-circuit shutdown. The latter uses the RUN/SS capacitor (CSS) as a timer: if VOUT falls below 70% of nominal for >CSS discharge time, the controller latches off until RUN/SS is recycled. This latchoff can be defeated with >5µA injected into RUN/SS.

Is the LTC1735IGN-1#PBF pin-compatible with other variants in the LTC1735 family?

Yes, the LTC1735IGN-1#PBF is pin-compatible with all members of the LTC1735-1 family (e.g., LTC1735CGN-1, LTC1735IS-1), sharing identical 16-pin SSOP/SO footprints and pin functions. Differences are limited to temperature grade (I-grade vs. C-grade) and package type (GN vs. S). No PCB redesign is required when substituting within the same package variant and grade.