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Date: 05/25/04

SP6203/6205 Low Noise, 300 and 500mA CMOS LDO Regulators

© Copyright 2004 Sipex Corporation

Note that the regulator cannot always be used at

its maximum current rating. For example, in a

5V input to 3.0V output application at an ambi-

ent temperature of 25

°C and operating at the full

limited to a much lower load current, deter-

mined by the following equation:

After calculation, we find that in such an appli-

cation (SP6205) the regulator is limited to

194.1mA. Doing the same calculations for the

300mA LDO (SP6203) will limit the regulator’s

output current to 194.4mA.

Also, taking advantage of the very low dropout

voltage characteristics of the SP6203/6205,

power dissipation can be reduced by using the

lowest possible input voltage to minimize the

input-to-output drop.

Adjustable Regulator Applications

The SP6203/6205 can be adjusted to a specific

output voltage by using two external resistors

(see functional diagram). The resistors set the

output voltage based on the following equation:

Resistor values are not critical because ADJ

(adjust) has a high input impedance, but for best

performance use resistors of 470K

Ω or less. A

improved noise performance.

Dual-Supply Operation

When used in dual supply systems where the

regulator load is returned to a negative supply,

the output voltage must be diode clamped to

ground.

Layout Considerations

The primary path of heat conduction out of the

package is via the package leads. Therefore,

careful considerations have to be taken into

account:

1) Attaching the part to a larger copper footprint

will enable better heat transfer from the device,

especially on PCB’s where there are internal

ground and power planes.

2) Place the input, output and bypass capacitors

close to the device for optimal transient re-

sponse and device behavior.

3) Connect all ground connections directly to

the ground plane. In case there’s no ground

plane, connect to a common local ground point

before connecting to board ground.

Such layouts will provide a much better thermal

conductivity (lower

allowable power dissipation limit.

THEORY OF OPERATION: Continued