Analog Devices Inc. LTC1771EMS8#TRPBF

Overview

LTC1771EMS8#TRPBF from Analog Devices (formerly Linear Technology) is a high-efficiency current-mode step-down DC/DC controller driving an external P-channel MOSFET, featuring 10µA no-load quiescent current, 2.8V–20V input range, and ±2% output voltage accuracy over temperature. It supports up to 5A output current with 100% duty cycle for ultra-low dropout operation and is optimized for battery-powered systems requiring extended runtime.

For engineers reviewing the LTC1771EMS8#TRPBF datasheet, LTC1771EMS8#TRPBF pinout, LTC1771EMS8#TRPBF application, or LTC1771EMS8#TRPBF equivalent, key selection considerations include its constant off-time architecture, Burst Mode™ enable/disable via MODE pin, programmable soft-start via RUN/SS, current-sense threshold tolerance (110–180mV), and thermal limits (T_JMAX = 125°C, θ_JA = 200°C/W in MS8).

Technical Context

The LTC1771EMS8#TRPBF implements a constant off-time, current-mode control architecture with a fixed 3.5µs minimum off-time that extends up to 70µs under low-V_FB conditions-enabling robust short-circuit protection and stable operation down to zero output voltage. Its error amplifier drives the ITH pin to regulate peak inductor current, while the internal 1.23V reference (±2% over –40°C to 85°C) sets output voltage via external resistor divider.

Burst Mode™ operation-enabled by pulling MODE ≥2V-reduces no-load supply current to 9µA typical by entering sleep mode when load drops below ~25% of full scale, then waking rapidly via ITH clamping and compensation capacitor reconnection. Shutdown reduces IQ to 2µA, and micropower RUN/SS control allows precise sequencing with 1µA soft-start charging current.

Key Specifications

Pinout & Package

Package: 8-Lead MSOP (MS8), 3mm × 3mm, 0.65mm pitch, exposed pad (not electrically connected). Thermal resistance θ_JA = 200°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC3866EMSE#PBF and TPS54202DRCT, the LTC1771EMS8#TRPBF uniquely combines P-MOS simplicity, 10µA no-load current, 100% duty cycle, and Burst Mode for longest battery life in sub-5A portable systems - at the cost of external FET and sense resistor.

Availability

LTC1771EMS8#TRPBF is available at Aetrix Electronics and suitable for cellular telephones, portable instruments, battery chargers, and wireless modems requiring stable component supply with guaranteed long-term availability and traceable sourcing.

Supply support for LTC1771EMS8#TRPBF 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 and maintains full product support, documentation, and manufacturing continuity for all Linear parts including the LTC series.

The LTC1771EMS8#TRPBF belongs to Linear's high-efficiency DC/DC controller family designed specifically for battery-powered portable equipment where ultralow quiescent current, wide input range, and flexible external FET selection are critical.

FAQ

What is the maximum output current supported by the LTC1771EMS8#TRPBF?

The LTC1771EMS8#TRPBF itself does not deliver output current-it controls an external P-channel MOSFET. With appropriate MOSFET and R_SENSE selection, the LTC1771EMS8#TRPBF supports up to 5A average output current. Peak current is set by ΔV_SENSE = 110–180mV across R_SENSE, and continuous operation depends on thermal design, inductor saturation rating, and MOSFET R_DS(ON). The datasheet confirms "Output Currents: Up to 5A" under typical operating conditions.

Does the LTC1771EMS8#TRPBF support 100% duty cycle operation, and why is this important?

Yes, the LTC1771EMS8#TRPBF supports 100% duty cycle operation, enabling regulation when V_IN approaches V_OUT-critical for maintaining output voltage as battery voltage declines. This feature allows uninterrupted operation down to V_IN ≈ V_OUT + V_F(catch diode), extending usable battery capacity in Li-ion-powered devices. The datasheet explicitly states "Very Low Dropout Operation: 100% Duty Cycle" as a key feature.

How does Burst Mode™ operation improve efficiency at light loads for the LTC1771EMS8#TRPBF?

Burst Mode™ reduces no-load supply current to 9µA typical by disabling non-essential circuitry (e.g., gate driver, oscillator) while keeping the 1.23V reference and error amplifier active. During light loads, the LTC1771EMS8#TRPBF enters sleep mode when ITH falls below 1V (~25% of full-scale current), then wakes rapidly when load increases. This preserves >85% efficiency at 1mA load-far exceeding standard PWM controllers-and directly enables multi-week battery standby.

What are the absolute maximum ratings for the SENSE pin on the LTC1771EMS8#TRPBF?

The SENSE pin on the LTC1771EMS8#TRPBF has voltage limits dependent on VIN: for VIN ≤ 12V, SENSE may range from –0.3V to (VIN + 0.3V); for VIN > 12V, SENSE must be between (VIN – 12V) and (VIN + 0.3V). Exceeding these ranges risks damage. The maximum sensed differential voltage is 180mV (ΔV_SENSE(MAX)), and the pin is designed for connection to an external R_SENSE between SENSE and VIN-not ground.

Can the LTC1771EMS8#TRPBF be used with N-channel MOSFETs, or is it limited to P-channel devices?

The LTC1771EMS8#TRPBF is designed exclusively for external P-channel MOSFETs, as confirmed by its PGATE driver topology (swinging from GND to VIN) and functional block diagram. It does not support N-channel high-side switches without additional level-shifting circuitry. Attempting to use an N-MOSFET would prevent proper gate drive and likely cause failure. For N-MOSFET compatibility, consider alternatives like the LTC3866 or TPS54202.