Analog Devices Inc. LTC3872IDDB-1#TRPBF

Overview

LTC3872IDDB-1#TRPBF from Analog Devices (formerly Linear Technology) is a constant-frequency current-mode boost DC/DC controller that drives an external N-channel MOSFET without requiring a sense resistor. It operates from 2.75V to 9.8V input, delivers up to 60V output, achieves ±1.5% output voltage accuracy, and switches at 550kHz for compact inductor sizing-used in telecom power supplies and IP phone power conversion.

For engineers reviewing the LTC3872IDDB-1#TRPBF datasheet, LTC3872IDDB-1#TRPBF pinout, LTC3872IDDB-1#TRPBF application, or LTC3872IDDB-1#TRPBF equivalent, key selection considerations include its No RSENSE architecture, adjustable current limit via IPRG pin, internal soft-start, pulse-skipping light-load operation, and DFN-8 (2mm × 3mm) thermal performance (θ_JA = 76°C/W).

Technical Context

The LTC3872IDDB-1#TRPBF implements a No RSENSE current sensing architecture by monitoring the voltage drop across the external MOSFET's R_DS(ON), eliminating discrete sense resistors and improving efficiency. Its constant-frequency 550kHz oscillator enables predictable EMI behavior and supports small magnetics.

It features a current-mode control loop with internal slope compensation, ±1.5% reference accuracy over –40°C to 125°C, undervoltage lockout at 2.3V (rising), and shutdown current of 8µA. The ITH pin serves as the error amplifier output and current threshold control node, while RUN/SS provides enable control and optional external soft-start via capacitor charging.

Key Specifications

Pinout & Package

Package: 8-lead (2mm × 3mm) plastic DFN with exposed pad (Pin 9 = GND, must be soldered). Thermal resistance θ_JA = 76°C/W enables higher power density than TSOT-23 variants.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC3872IDDB-1#TRPBF, the E-grade alternative offers lower cost but reduced thermal margin, while the H-grade provides extended reliability at elevated temperatures - all share identical electrical specs, No RSENSE architecture, and DFN-8 footprint.

Availability

LTC3872IDDB-1#TRPBF is available at Aetrix Electronics and suitable for telecom power supplies, IP phone power conversion, and 42V automotive systems requiring stable component supply, long-term lifecycle support, and guaranteed industrial temperature performance.

Supply support for LTC3872IDDB-1#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 DC/DC controller families.

The LTC3872IDDB-1#TRPBF belongs to Linear's No RSENSE boost controller product line, designed specifically for high-efficiency, low-component-count DC/DC boost, SEPIC, and flyback converters in space-constrained industrial and communications equipment.

FAQ

What is the maximum output voltage supported by the LTC3872IDDB-1#TRPBF?

The LTC3872IDDB-1#TRPBF supports output voltages up to 60V, as confirmed by its SW pin absolute maximum rating and validated in typical application circuits. This enables use in high-voltage boost configurations such as 3.3V-to-48V telecom supplies. The actual achievable VOUT depends on external MOSFET BVDSS, diode rating, and layout parasitics - design margin should be maintained per manufacturer recommendations.

Does the LTC3872IDDB-1#TRPBF require an external current sense resistor?

No, the LTC3872IDDB-1#TRPBF uses No RSENSE architecture to sense current through the R_DS(ON) of the external N-channel MOSFET, eliminating the need for a discrete sense resistor. This reduces power loss, board area, and component count. The SW pin serves as the current sense input, with internal circuitry interpreting the MOSFET's voltage drop to regulate peak inductor current.

What is the purpose of the IPRG pin on the LTC3872IDDB-1#TRPBF?

The IPRG pin on the LTC3872IDDB-1#TRPBF selects the peak current limit threshold: grounding it sets ~80mV, floating sets ~150mV, and connecting to VIN sets ~260mV (values vary by grade). This adjusts the maximum allowable MOSFET conduction voltage drop, directly determining current limit without external components - enabling flexible overcurrent protection tailored to MOSFET R_DS(ON).

Can the LTC3872IDDB-1#TRPBF operate in discontinuous conduction mode (DCM)?

Yes, the LTC3872IDDB-1#TRPBF naturally transitions into discontinuous conduction mode at light loads due to its current-mode architecture and pulse-skipping behavior. During DCM, the inductor current falls to zero each cycle, and the controller maintains regulation without frequency foldback. This preserves low output ripple and avoids audible noise - unlike voltage-mode controllers that may exhibit subharmonic instability in DCM.

What thermal considerations apply to the LTC3872IDDB-1#TRPBF in its DFN package?

The LTC3872IDDB-1#TRPBF in the 8-lead DFN (2mm × 3mm) package has θ_JA = 76°C/W when the exposed pad (Pin 9) is properly soldered to a thermal pad on the PCB. To maintain operation within its –40°C to +125°C junction range, ensure ≥100mm² copper area under the pad, use ≥4 thermal vias, and avoid enclosing the IC in thermally restrictive enclosures. Derate output current above 85°C ambient per thermal simulation.