SUPPLIER

PHONE

WEBSITE

Fairchild Semiconductor

888-522-5372

www.fairchildsemi.com

HALO Electronics, Inc.

650-903-3800

www.haloelectronics.com

Murata Electronics North America, Inc.

770-436-1300

www.murata-northamerica.com

_________________________________________________________________ Maxim Integrated Products 2

MAX13256 Evaluation Kit

Evaluates: MAX13256

Quick Start

Required Equipment

•

MAX13256EVkit

•

+24V,1ADCpowersupply

•

Electronicloadcapableof200mA

•

Ammeter

•

Voltmeter

Procedure

The EV kit is fully assembled and tested. Follow the steps

below to verify board operation. Caution: Do not turn on

the power until all connections are completed.

1)

Verify that jumpers JU1, JU2, and JU4 are in their

default positions, as shown in Tables 1, 2, and 3.

2)

Set the DC power supply to 24V.

3)

Set the electronic load to 200mA and disable

the output.

4)

Connect the voltmeter between the +VOUT and

SGND PCB pads on the EV kit.

5)

Connect the ammeter between the +VOUT PCB

pad on the EV kit and the positive terminal on the

electronic load. The negative terminal on the

electronic load is connected to the SGND PCB pad

on the EV kit.

6)

Connect the power supply between the VDD and

GND PCB pads on the EV kit.

7)

Turn on the power supply.

8)

Enable the electronic load.

9)

Verify that the ammeter reads approximately 200mA.

10) Verify that the voltmeter reads approximately 22.8V.

Detailed Description

The MAX13256 EV kit is a 10W, isolated H-bridge DC-DC

converter that provides an unregulated output that is

two diode-voltage drops less than its input supply,

with respect to the isolated ground. In the default

configuration, the maximum load is limited by the device

and the on-board transformer.

The device 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 transformer’s primary winding.

The device can be operated using the internal 425kHz

oscillator, or driven by an external clock to synchronize

multiple devices and control EMI behavior. Regardless

of the clock source being used, an internal flip-flop

stage guarantees a fixed 50% duty cycle, preventing DC

current flow in the transformer as long as the clock’s

period is constant.

The device operates from a single-supply voltage and

includes UVLO and an active-low enable input for

controlled startup. If the input voltage at VDD falls below

6.3V, or the EN input is pulled above 2V, the device shuts

down and ST1 and ST2 are high impedance.

The device features an adjustable output current limit

at the transformer driver outputs (ST1 and ST2). When

the current reaches the limit for longer than the 1.2ms

blanking time, the drive outputs are disabled and

the FAULT output asserts. The drivers are reenabled

after the 38.2ms autoretry time. If a continuous fault

condition is present, the duty cycle of the fault current is

approximately 3%.

with 300 mil spacing between the GND and SGND

planes. The bottom PCB GND plane under device U1

is utilized as a thermal heatsink for power dissipation

of the device’s thermally enhanced TDFN package with

exposed pad. Test points GND and SGND are provided

on the PCB for probing the respective ground planes, or

to connect the GND and SGND planes for nonisolated

evaluation of the circuit.

Clock Source

The device has two modes of operation: internal

oscillator or external clock. To use the internal 425kHz

oscillator, place a shunt in the 1-2 position on jumper

JU2. When using an external clock, remove the shunt

from JU2 and apply a clock signal on the CLK PCB

pad on the EV kit. An internal flip-flop divides the

external clock by two, generating a switching signal with a

guaranteed 50% duty cycle. As a result, the device

outputs switch at 1/2 the external clock frequency.

Component Suppliers

Note: Indicate that you are using the MAX13256 when contacting these component suppliers.