MAX13256 Datasheet, PDF(8/17 Page) Maxim Integrated Products – 36V H-Bridge Transformer Driver for Isolated Supplies Integrated System Protection

◁

MAX13256

36V H-Bridge Transformer

Driver for Isolated Supplies

Functional Diagram

VDD

MAX13256

OSC

UVLO

VUVLO

CLK

ITH

FAULT

MUX

FLIP-

FLOP

MOSFET

H-BRIDGE

DRIVER

WATCHDOG

CURRENT

LIMIT

VDD

ST1

VDD

ST2

GND

Detailed Description

The MAX13256 is an integrated primary-side controller

and H-bridge driver for isolated power-supply circuits.

The device contains an on-board oscillator, protec-

tion circuitry, and internal MOSFETs to provide up to

300mA of current to the primary winding of a trans-

former. The device can be operated using the internal

oscillator or driven by an external clock to synchronize

multiple MAX13256 devices and control EMI behavior.

Regardless of the clock source being used, an internal

flip-flop stage guarantees a fixed 50% duty cycle to

prevent DC current flow in the transformer as long as the

period of the clock is constant.

The device operates from a wide single-supply voltage

of 8V to 36V, and includes undervoltage lockout for con-

trolled startup. The device features break-before-make

switching to prevent cross conduction of the H-bridge

MOSFETs. An external resistor sets an overcurrent limit,

allowing primary-side limiting of load currents on the

transformerâs secondary side. Thermal-shutdown cir-

cuitry provides additional protection against excessive

power dissipation.

Isolated Power Supply

The MAX13256 allows a versatile range of secondary-

side rectification circuits (see Figure 3). The primary-to-

secondary transformer winding ratio can be chosen to

adjust the isolated output voltage. The device delivers

up to 300mA of current to the transformer with a supply

up to +36V.

The MAX13256 provides the advantages of the H-bridge

converter topology, including multiple isolated outputs,

step-up/step-down or inverted output, relaxed filtering

requirements, and low output ripple.

▷