Analog Devices Inc. LTC3225EDDB-1#TRMPBF

Overview

LTC3225EDDB-1#TRMPBF from Analog Devices (formerly Linear Technology) is a programmable supercapacitor charger IC designed to charge two series-connected supercapacitors to precisely 4.0V or 4.5V from 2.8V–5.5V input supplies. It delivers up to 150mA output current, features automatic cell balancing without external resistors, and operates in a compact 10-lead 2mm × 3mm DFN package. It is used in backup power systems for real-time clocks and low-power microcontrollers.

For engineers reviewing the LTC3225EDDB-1#TRMPBF datasheet, LTC3225EDDB-1#TRMPBF pinout, LTC3225EDDB-1#TRMPBF application, or LTC3225EDDB-1#TRMPBF equivalent, key selection criteria include per-cell voltage regulation (2.0V/2.25V), shutdown current (<1μA when input removed), PGOOD status signaling, and compatibility with 1μF flying capacitor and single-resistor charge current programming.

Technical Context

The LTC3225EDDB-1#TRMPBF implements a constant-frequency switched-capacitor charge pump topology operating at 0.6–1.5MHz, enabling low-noise, inductorless voltage doubling. Its internal architecture continuously monitors CX (midpoint) voltage to enforce equal voltage distribution across both supercapacitors during charging.

It integrates UVLO (2.0V–2.45V threshold), thermal shutdown (~150°C), overcurrent protection, and a high-impedance open-drain PGOOD output that asserts low when VOUT falls >7.2% below regulation. The VSEL pin selects between 4.0V and 4.5V output, corresponding to 2.0V or 2.25V per cell.

Key Specifications

Pinout & Package

The LTC3225EDDB-1#TRMPBF is housed in a 10-lead plastic DFN package (3mm × 2mm) with exposed thermal pad (Pin 11) that must be soldered to a low-impedance PCB ground plane. Pin 8 (GND) and Pin 11 (exposed pad) are internally connected and serve as the primary ground reference and thermal path.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC3204-5 and LTC3221-5, the LTC3225EDDB-1#TRMPBF uniquely combines programmable dual-cell regulation (4.0V/4.5V), automatic balancing, and 150mA capability in a 2mm × 3mm DFN-making it the only option among the three qualified for unbalanced, high-current supercapacitor backup systems.

Availability

LTC3225EDDB-1#TRMPBF is available at Aetrix Electronics and suitable for real-time clock backup, low-power microcontroller hold-up, and energy-harvesting storage applications requiring stable component supply, long-term lifecycle support, and guaranteed traceability.

Supply support for LTC3225EDDB-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 portfolio. Linear pioneered high-performance switching regulators and charge pumps for demanding industrial and automotive applications.

The LTC3225EDDB-1#TRMPBF belongs to Linear's supercapacitor charger product line, engineered specifically for reliable, resistor-programmable charging of series-connected supercapacitors in battery-free or battery-assisted backup systems.

FAQ

What is the maximum supercapacitor stack voltage supported by the LTC3225EDDB-1#TRMPBF?

The LTC3225EDDB-1#TRMPBF supports a maximum series stack voltage of 4.5V, selectable via the VSEL pin. This corresponds to 2.25V per supercapacitor - a value chosen to stay within the safe operating voltage limit of most 2.7V-rated supercapacitors during full charge, preventing accelerated aging or failure.

How does the LTC3225EDDB-1#TRMPBF achieve automatic cell balancing without external components?

The LTC3225EDDB-1#TRMPBF achieves automatic cell balancing by continuously monitoring the CX pin (midpoint voltage between the two series supercapacitors) and dynamically adjusting charge current to each cell. When voltage imbalance is detected, it increases current to the lower-voltage cell and decreases current to the higher-voltage cell - all using internal circuitry, eliminating the need for power-wasting balancing resistors.

Can the LTC3225EDDB-1#TRMPBF be used to charge a single supercapacitor?

Yes, the LTC3225EDDB-1#TRMPBF can charge a single supercapacitor by connecting two matched ≥100μF ceramic capacitors in series and placing them in parallel with the supercapacitor. This creates an artificial "dual-cell" configuration that allows the IC's balancing architecture to function while delivering regulated voltage to the single device.

What is the minimum flying capacitor value required for full 150mA operation of the LTC3225EDDB-1#TRMPBF?

The LTC3225EDDB-1#TRMPBF requires a minimum 0.6μF flying capacitor (CFLY) to deliver its full rated 150mA output current. A 1μF X5R or X7R ceramic capacitor is recommended to maintain sufficient effective capacitance across temperature and DC bias, ensuring stable regulation and efficiency.

Does the LTC3225EDDB-1#TRMPBF provide reverse current blocking when the input supply is removed?

Yes, the LTC3225EDDB-1#TRMPBF provides reverse current blocking: when VIN is removed or grounded while supercapacitors remain charged, the device draws less than 1μA from COUT. This is achieved through internal MOSFET control and isolation, preserving stored energy and enabling long backup duration without external diodes or FETs.