Analog Devices Inc./Maxim Integrated MAX13256ATB+

Overview

MAX13256ATB+ from Analog Devices is a 36V H-bridge transformer driver IC for isolated DC/DC power supplies up to 10W, delivering up to 300mA primary-side current from an 8V–36V supply, featuring adjustable overcurrent limiting via external resistor, fixed 50% duty cycle, and fault reporting via open-drain FAULT pin - used in PLC 24V supply isolation and isolated fieldbus interfaces.

For engineers reviewing the MAX13256ATB+ datasheet, MAX13256ATB+ pinout, MAX13256ATB+ application, or MAX13256ATB+ equivalent, this page delivers verified technical context, real-world operating parameters, validated alternative options, and design-critical package and timing details - all confirmed against the official Analog Devices MAX13256 datasheet (Rev 2, 9/21).

Technical Context

The MAX13256ATB+ integrates dual N-channel MOSFET drivers with break-before-make switching logic and internal flip-flop control to guarantee a fixed 49–51% duty cycle regardless of clock source - eliminating transformer core saturation risk. It supports both internal oscillator mode (425kHz typ) and external clock synchronization (200–2000kHz input, output at half frequency).

Protection architecture includes programmable overcurrent limiting (via ITH pin and RLIM resistor), thermal shutdown at +160°C with 10°C hysteresis, undervoltage lockout (6.3V typ threshold), and watchdog timeout (20–55μs) to recover from stalled clocks - all implemented without external supervision circuitry.

Key Specifications

Pinout & Package

MAX13256ATB+ is housed in a 10-pin 3mm × 3mm TDFN-EP package (package code T1033+1) with exposed pad thermally connected to GND - requires soldering to large copper pour for θJA = 41°C/W (four-layer board).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar H-bridge transformer driver applications.

Compared with LM5122MH/NOPB and UCC28911DR, the MAX13256ATB+ uniquely integrates a matched H-bridge, 50% duty control, and fault signaling in a 3mm × 3mm package - making it optimal for space-constrained, medium-power isolated supplies requiring simplicity and reliability without secondary feedback.

Availability

MAX13256ATB+ is available at Aetrix Electronics and suitable for power meters, isolated fieldbus interfaces, and 24V PLC supply isolation requiring stable component supply across automotive and industrial temperature ranges.

Supply support for MAX13256ATB+ 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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving precision instrumentation, industrial automation, and automotive markets.

The MAX13256ATB+ belongs to Analog Devices' isolated power IC portfolio, engineered specifically for compact, high-reliability transformer-driven isolated DC/DC converters in harsh environments - emphasizing integration, protection, and ease of compliance.

FAQ

What is the maximum transformer primary current supported by the MAX13256ATB+?

The MAX13256ATB+ supports up to 300mA typical continuous current into the transformer primary winding, with ±850mA absolute maximum output current capability on ST1/ST2 pins. The actual delivered current depends on supply voltage, transformer turns ratio, and RLIM-selected overcurrent threshold - e.g., with RLIM = 1kΩ, the current limit is 650mA (typ), allowing robust headroom for transient loads.

How does the MAX13256ATB+ ensure transformer safety during clock failure?

The MAX13256ATB+ incorporates an internal watchdog timer with 20–55μs timeout. If the CLK signal stalls, the device automatically switches to its internal 425kHz oscillator within one watchdog period - maintaining 50% duty cycle switching and preventing dangerous DC current buildup in the transformer primary that could cause saturation or overheating.

Can the MAX13256ATB+ be used with an external clock, and what frequency range is supported?

Yes, the MAX13256ATB+ accepts external clock signals from 200kHz to 2000kHz on the CLK pin. The internal circuitry divides this by two, so the ST1/ST2 outputs switch at exactly half the input clock frequency - enabling precise EMI control and synchronization of multiple MAX13256ATB+ devices in multi-output isolated supplies.

What is the role of the ITH pin on the MAX13256ATB+, and how is it configured?

The ITH pin on the MAX13256ATB+ sets the overcurrent threshold via an external resistor (RLIM) connected to GND. Using RLIM(kΩ) = 650 / ILIM(mA), designers select trip points from 165mA to 800mA. For example, a 1kΩ 1% resistor configures ILIM = 650mA (typ), providing primary-side current limiting without secondary feedback components.

Does the MAX13256ATB+ require special PCB layout considerations for thermal performance?

Yes - the MAX13256ATB+ TDFN-EP package includes an exposed pad internally tied to GND. To achieve θJA = 41°C/W (four-layer board), the pad must be soldered to ≥200mm² of inner/outer layer copper connected via ≥6 thermal vias (0.3mm diameter) to internal ground planes - critical for sustaining 10W operation at +125°C ambient.