LM2575 datasheet(7/28 Pages) MOTOROLA

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LM2575

MOTOROLA ANALOG IC DEVICE DATA

Figure 14. Typical Test Circuit

1N5819

330

µH

Output

Feedback

Cout

330

µF

/16 V

Cin

100

µF/50 V

LM2575–5

3ON/OFF

Gnd

Vin

Load

Vout

Regulated

Output

Vin

Unregulated

DC Input

8.0 V – 40 V

1N5819

330

µH

Output

Feedback

Cout

330

µF

/16 V

Cin

100

µF/50 V

LM2575

Adjustable

3ON/OFF

Gnd

Vin

Load

Vout

Regulated

Output

Unregulated

DC Input

8.0 V – 40 V

5.0 Output Voltage Versions

Adjustable Output Voltage Versions

Vout + Vref 1 )

+ R1

Vout

ref

–1

Where Vref = 1.23 V, R1

between 1.0 k

Ω and 5.0 kΩ

–

PCB LAYOUT GUIDELINES

As in any switching regulator, the layout of the printed

circuit board is very important. Rapidly switching currents

associated with wiring inductance, stray capacitance and

parasitic inductance of the printed circuit board traces can

generate voltage transients which can generate

electromagnetic interferences (EMI) and affect the desired

operation. As indicated in the Figure 14, to minimize

inductance and ground loops, the length of the leads

indicated by heavy lines should be kept as short as possible.

For best results, single–point grounding (as indicated) or

ground plane construction should be used.

On the other hand, the PCB area connected to the Pin 2

(emitter of the internal switch) of the LM2575 should be kept

to a minimum in order to minimize coupling to sensitive

circuitry.

Another sensitive part of the circuit is the feedback. It is

important to keep the sensitive feedback wiring short. To

assure this, physically locate the programming resistors near

to the regulator, when using the adjustable version of the

LM2575 regulator.

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