DC511A Quick Start Guide Datasheet by Analog Devices Inc.

L7 ”NW

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC511

LOW NOISE SWITCHING POWER SUPPLY

LT3439

DESCRIPTION

Demonstration circuit 511 shows how a power sup-

ply’s conducted and radiated EMI can be reduced sig-

nificantly by using the LT3439 to control the voltage

and current slew rates of its internal power switches.

DC511 employs a push-pull topology which is inher-

ently less noisy than most other topologies and the

high frequency EMI is reduced by as much as 40dB

by slewing the switching currents and voltages. The

design is well suited to noise sensitive systems such

as medical instruments, industrial sensing and con-

trol, data conversion and wide band communications.

DC511 produces isolated 12Vout and –12Vout at up

to 80mA each from 5Vin. The board can be modified,

by changing the transformer, to produce output volt-

ages less than the input voltage. Output voltage regu-

lation is directly proportional to input voltage regula-

tion since there is no output feedback. DC511 uses a

potentiometer that sets the slew rates of the power

switches, allowing the user to observe the benefit of

slew rate control, and to examine the tradeoff be-

tween noise performance and circuit efficiency.

Design files for this circuit board are available. Call

the LTC factory.

QUICK START PROCEDURE

DC511 is easy to set up to evaluate the performance

of the LT3439. Refer to Figure 1 for proper measure-

ment equipment setup and follow the procedure be-

low:

Connect Load 1 between the +Vout (E2) and Gnd

(E3) terminals and another Load 2 between the –

Vout (E4) and Gnd (E3) terminals.

Apply 5V between the Vin (E1) and Gnd (E6) termi-

nals.

To measure the output noise, connect one end of a

BNC cable to the BNC connector J1. Connect the

other end of the BNC cable to an oscilloscope with

a 50Ω input impedance. Refer to Application Note

AN70 for more precise techniques for measuring

the output noise.

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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC511

LOW NOISE SWITCHING POWER SUPPLY

Figure 1. Proper Measurement Equipment Setup

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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT DC511

LOW NOISE SWITCHING POWER SUPPLY

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