Analog Devices Inc. LTC3721EUF-1#TRPBF

Overview

LTC3721EUF-1#TRPBF from Analog Devices (formerly Linear Technology) is a high-efficiency, 1.5A sink / 1A source push-pull PWM controller for isolated DC/DC converters. It delivers peak current mode control with programmable slope compensation, adjustable dead-time (90–300ns), and integrated 5V reference (±0.5% initial accuracy). Designed for telecom infrastructure and server power supplies, it operates up to 1MHz switching frequency with <50% duty cycle symmetry.

For engineers reviewing the LTC3721EUF-1#TRPBF datasheet, LTC3721EUF-1#TRPBF pinout, LTC3721EUF-1#TRPBF application, or LTC3721EUF-1#TRPBF equivalent, key selection considerations include its 16-pin 4mm × 4mm QFN package with exposed GND pad, VCC UVLO (10.25V turn-on), system UVLO programmability (5.0V threshold), and hiccup-mode short-circuit protection with 13µA soft-start current.

Technical Context

The LTC3721EUF-1#TRPBF implements fixed-frequency, pulse-by-pulse peak current mode control using an internal oscillator ramp (2.35V p-p on CT) and dual comparators on CS (300mV pulse-by-pulse limit, 600mV shutdown threshold). Its error amplifier features 70–90dB open-loop gain and 1.2V FB input reference, enabling precise voltage regulation in isolated flyback-derivative topologies.

Dead-time is set via external resistor between DPRG and VREF (2V nominal), generating 90–300ns delay; leading edge blanking is independently programmed via RLEB-to-GND (40–320ns). The IC integrates a 10.3V shunt regulator (40mA sink), 5V LDO (15mA), and low start-up current (230µA max) for auxiliary winding bias compatibility.

Key Specifications

Pinout & Package

Package: 16-lead (4mm × 4mm) plastic QFN with exposed thermal pad (Pin 17 = GND, must be soldered).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar push-pull controller applications.

Compared with UCC2897A and MAX5069B, the LTC3721EUF-1#TRPBF uniquely combines programmable dead-time, integrated 10.3V VCC shunt, and hiccup-mode protection-enabling robust, high-power push-pull designs without external support circuitry.

Availability

LTC3721EUF-1#TRPBF is available at Aetrix Electronics and suitable for telecom infrastructure power systems, server VRM auxiliary supplies, and industrial distributed power modules requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LTC3721EUF-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 its high-performance analog and power management portfolio.

The LTC3721EUF-1#TRPBF belongs to Linear's isolated power controller family, engineered specifically for compact, high-efficiency push-pull DC/DC converters in telecom, server, and industrial applications.

FAQ

What is the maximum operating frequency of the LTC3721EUF-1#TRPBF?

The LTC3721EUF-1#TRPBF oscillator operates up to 1MHz, producing a 2.35V p-p ramp on the CT pin. Since the push-pull outputs switch at half the oscillator frequency, the maximum effective switching frequency is 500kHz. This allows use of smaller magnetics while maintaining stability through programmable slope compensation.

How does the LTC3721EUF-1#TRPBF implement dead-time control?

The LTC3721EUF-1#TRPBF uses the DPRG pin to program dead-time between DRVA and DRVB outputs. A resistor from DPRG to VREF (2V nominal) sets a current that determines delay duration from 90ns to 300ns. An internal 10µA current source ensures minimum dead-time if DPRG is left floating, preventing shoot-through in push-pull MOSFET stages.

Can the LTC3721EUF-1#TRPBF be powered directly from an auxiliary transformer winding?

Yes - the LTC3721EUF-1#TRPBF supports direct auxiliary winding bias via its integrated 10.3V VCC shunt regulator. With only 230µA typical start-up current, it works with high-value trickle-charge resistors (e.g., 430kΩ for off-line inputs). The 4.2V UVLO hysteresis ensures reliable operation even with loosely regulated windings.

What protection features does the LTC3721EUF-1#TRPBF include?

The LTC3721EUF-1#TRPBF provides pulse-by-pulse current limiting (300mV threshold), hiccup-mode short-circuit shutdown (600mV threshold), overtemperature protection, and programmable UVLO. During overload, it discharges the SS pin and initiates soft-start retry cycles - protecting MOSFETs, transformer, and output capacitors without requiring external fault-handling circuitry.

Is the LTC3721EUF-1#TRPBF pin-compatible with the SSOP-packaged LTC3721EGN-1?

No - the LTC3721EUF-1#TRPBF uses a 16-pin 4mm × 4mm QFN package with separate PGND (Pin 4) and SGND (Pin 5) pins plus exposed thermal pad (Pin 17), whereas the LTC3721EGN-1 uses a 16-lead narrow SSOP with shared GND. Pin functions match, but layout, thermal design, and grounding strategy differ significantly between packages.