Analog Devices Inc. LT3484EDCB-1#TRMPBF

Overview

LT3484EDCB-1#TRMPBF from Analog Devices (formerly Linear Technology) is a photoflash capacitor charger IC with integrated NPN power switch, designed for compact digital camera and mobile phone flash systems. It delivers 225mA average input current, supports 1.7V–16V input range (including two AA cells), and charges photoflash capacitors to 320V using transformer-based flyback topology without external Schottky diode or output voltage divider.

For engineers reviewing the LT3484EDCB-1#TRMPBF datasheet, LT3484EDCB-1#TRMPBF pinout, LT3484EDCB-1#TRMPBF application, or LT3484EDCB-1#TRMPBF equivalent, key selection criteria include its 0.7A peak switch current limit, 6-pin 2mm × 3mm DFN package, DONE/CHARGE control interface, and transformer turns-ratio–determined output voltage regulation.

Technical Context

The LT3484EDCB-1#TRMPBF implements a patented flyback controller architecture with internal NPN power switch and dual comparator-based regulation: a VOUT comparator (trip at 31.5V above VIN) halts charging when target output is reached, while a DCM comparator (trip at 10–120mV above VIN) enables discontinuous conduction mode restart. Its 0.55A typical switch current limit defines energy per cycle and directly governs charge time for given capacitor size and input voltage.

Operation requires no external feedback network-output voltage is set solely by transformer turns ratio N = (VOUT + 2)/31.5-and integrates VBAT and VIN undervoltage lockout. The CHARGE pin provides synchronous start/stop control, and the open-collector DONE pin signals completion with NPN sink capability.

Key Specifications

Pinout & Package

The LT3484EDCB-1#TRMPBF is housed in a 6-lead plastic DFN package (2mm × 3mm, 0.75mm height) with exposed thermal pad (Pin 7) soldered to PCB ground for thermal management.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LT3468EDD-1#TRMPBF and LT3420EDD#TRPBF, the LT3484EDCB-1#TRMPBF uniquely supports dual-input (VIN + VBAT) operation for flexible battery architectures, achieves optimal balance of size, efficiency, and input current control in 2mm × 3mm DFN, and eliminates external feedback components entirely.

Availability

LT3484EDCB-1#TRMPBF is available at Aetrix Electronics and suitable for mobile phone flash modules, digital camera auxiliary lighting, and USB-powered portable flash units requiring stable component supply, long-lifecycle support, and guaranteed lead-free compliance.

Supply support for LT3484EDCB-1#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 its precision analog and power management product lines with full technical documentation and application support.

The LT3484EDCB-1#TRMPBF belongs to Linear's photoflash capacitor charger family, engineered specifically for space-constrained, battery-powered imaging systems requiring fast, efficient, and self-contained high-voltage generation.

FAQ

What is the peak switch current limit of the LT3484EDCB-1#TRMPBF?

The LT3484EDCB-1#TRMPBF has a typical peak switch current limit of 0.55A, with a minimum of 0.45A and maximum of 0.65A across temperature. This value defines the energy delivered per switching cycle and directly determines the 225mA average input current at 3.6V input, making it ideal for low-drain photoflash applications where battery life is critical. The LT3484EDCB-1#TRMPBF uses this fixed current limit to regulate charge rate without external sensing resistors.

How does the LT3484EDCB-1#TRMPBF set output voltage without external resistors?

The LT3484EDCB-1#TRMPBF sets output voltage exclusively through transformer turns ratio N using the equation VOUT = 31.5 × N − 2V. Its internal VOUT comparator triggers at 31.5V above VIN on the SW pin, eliminating need for external voltage dividers. This method ensures stable regulation independent of resistor tolerance or temperature drift. The LT3484EDCB-1#TRMPBF thus achieves precise 320V output with N = 10.2, as verified in typical application circuits.

Can the LT3484EDCB-1#TRMPBF operate from two AA batteries?

Yes, the LT3484EDCB-1#TRMPBF supports dual AA battery operation via its dedicated VBAT pin, which accepts 1.7V–16V. With alkaline cells (1.5V nominal), it functions across the full 2.4V–3.2V discharge range while maintaining regulated 320V output. The LT3484EDCB-1#TRMPBF uses VBAT for transformer primary return and VIN for internal bias, enabling efficient dual-rail utilization not possible with single-supply alternatives.

What is the function of the DONE pin on the LT3484EDCB-1#TRMPBF?

The DONE pin on the LT3484EDCB-1#TRMPBF is an open-collector NPN output that sinks current when the target output voltage is reached, pulling the pin low to signal charge completion. It requires an external pull-up resistor (e.g., 100kΩ to VIN) and interfaces directly with microcontrollers for timing-critical flash triggering. The LT3484EDCB-1#TRMPBF asserts DONE only after VOUT stabilization, ensuring reliable synchronization without false triggers from transient overshoot.

Which transformer parameters are critical for reliable LT3484EDCB-1#TRMPBF operation?

Critical transformer parameters for the LT3484EDCB-1#TRMPBF include primary inductance ≥10µH, leakage inductance ≤500nH, and turns ratio N = 10.2 for 320V output. Exceeding 40V flyback spike on the SW pin (due to excessive leakage) risks premature shutdown or damage, while insufficient LPRI causes inadequate response to the flyback waveform. The LT3484EDCB-1#TRMPBF datasheet specifies pre-qualified parts like TDK LDT565630T-002 to guarantee compliance.