Analog Devices Inc. LT3484EDCB-0#TRMPBF

Overview

LT3484EDCB-0#TRMPBF from Analog Devices (formerly Linear Technology) is a photoflash capacitor charger IC designed for space-constrained digital camera and mobile phone flash systems. It integrates a patented flyback controller with an internal 1.4A NPN power switch, operates from 1.7V–16V input (including two AA cells), delivers up to 320V output via transformer turns-ratio-based voltage regulation, and achieves 4.6s charge time for 100µF at 320V from 3.6V input.

For engineers reviewing the LT3484EDCB-0#TRMPBF datasheet, LT3484EDCB-0#TRMPBF pinout, LT3484EDCB-0#TRMPBF application, or LT3484EDCB-0#TRMPBF equivalent, key selection criteria include peak switch current limit (1.4A), VOUT detection method (SW–VIN comparator trip at 31.5V), CHARGE/DONE control interface timing, DFN-6 (2mm × 3mm) thermal performance, and compatibility with compact 5.8mm × 5.8mm × 3mm transformers.

Technical Context

The LT3484EDCB-0#TRMPBF implements a fixed-frequency discontinuous conduction mode (DCM) flyback topology using an internal NPN power switch and proprietary current-mode control. Output voltage is regulated by monitoring the reflected flyback voltage on the SW pin relative to VIN, with a precise 31.5V comparator threshold that sets final charge voltage via transformer turns ratio (N = (VOUT + 2)/31.5).

It features dual supply inputs (VIN and VBAT), independent undervoltage lockout on both rails, open-collector DONE indication, active-low CHARGE enable, and integrated DCM detection to sustain switching until secondary current falls below threshold. The device requires no external Schottky clamp diode or output voltage divider.

Key Specifications

Pinout & Package

The LT3484EDCB-0#TRMPBF is housed in a thermally enhanced 6-lead plastic DFN package (2mm × 3mm) with exposed GND pad (Pin 7) requiring solder connection to PCB for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar photoflash capacitor charger applications.

Compared with LT3468EDD-0#TRMPBF, the LT3484EDCB-0#TRMPBF offers superior thermal performance in ultra-thin designs due to its exposed-pad DFN; versus LT3420EMS#TRPBF, it provides simpler control (no top-off complexity) and smaller footprint, making it optimal for cost- and space-sensitive consumer flash systems.

Availability

LT3484EDCB-0#TRMPBF is available at Aetrix Electronics and suitable for smartphone flash modules, digital camera auxiliary lighting, portable medical imaging devices, and industrial machine vision illumination requiring stable component supply and long-term manufacturability.

Supply support for LT3484EDCB-0#TRMPBF 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 former Linear parts including the LT3484 family.

The LT3484 series was developed specifically for miniaturized photoflash charging in battery-powered imaging devices, emphasizing ultra-small transformer compatibility, no-external-component voltage regulation, and precise input current control.

FAQ

What is the maximum output voltage achievable with LT3484EDCB-0#TRMPBF?

The LT3484EDCB-0#TRMPBF does not have a fixed maximum output voltage - it is determined by transformer turns ratio using the formula N = (VOUT + 2)/31.5. With standard 10.2:1 transformers, 320V is typical; higher ratios (e.g., 12:1) enable up to ~360V, provided SW pin voltage remains ≤40V during flyback and isolation ratings are maintained.

Can LT3484EDCB-0#TRMPBF operate from a single Li-ion cell?

Yes - the LT3484EDCB-0#TRMPBF supports VBAT down to 1.7V and VIN down to 2.5V. When powered from a single Li-ion cell (2.7V–4.2V), it delivers full 320V output with charge times scaling per Figure G04–G06; however, average input current increases to ~700mA at 2.7V, requiring careful thermal design and battery capacity planning.

How does the DONE pin function in LT3484EDCB-0#TRMPBF circuits?

The DONE pin on LT3484EDCB-0#TRMPBF is an open-collector NPN output that pulls low when the target output voltage is reached. It requires an external pull-up resistor (typically 100kΩ to VIN). The pin goes low only after VSW–VIN exceeds 31.5V and stays low until CHARGE is pulled low, providing unambiguous end-of-charge signaling to the host system.

Why does LT3484EDCB-0#TRMPBF require separate VIN and VBAT pins?

The LT3484EDCB-0#TRMPBF uses separate VIN and VBAT pins to decouple logic supply (VIN) from transformer primary return (VBAT), enabling independent optimization: VIN powers internal comparators and logic at stable voltage, while VBAT directly sources the high-current transformer primary path. This separation improves efficiency, reduces noise coupling, and allows battery-sourced primary drive even when VIN is derived from a DC/DC converter.

What transformer parameters are critical for reliable LT3484EDCB-0#TRMPBF operation?

Critical transformer parameters for LT3484EDCB-0#TRMPBF include: turns ratio (N = (VOUT + 2)/31.5), primary inductance (>5µH), primary leakage inductance (100–300nH), and isolation voltage (>500V). Exceeding 40V on the SW pin during turn-off - caused by excessive leakage inductance - risks malfunction; verified pre-designed units like TDK LDT565630T-001 meet all specifications for 320V operation.