Load-Transient Considerations

The MAX8559 load-transient response graphs (see the

Typical Operating Characteristics) show two compo-

nents of the output response: a DC shift in the output

voltage due to the different load currents and the tran-

sient response. Typical overshoot for step changes in

the load current from 10µA to 100mA is 15mV. Increase

the output capacitor’s value and decrease its ESR to

attenuate transient spikes.

Dropout Voltage

A regulator’s minimum input-output voltage differential

(or dropout voltage) determines the lowest usable sup-

ply voltage. In battery-powered systems, this determines

the useful end-of-life battery voltage. Because the

MAX8559 uses an internal P-channel MOSFET pass

transistor, its dropout voltage is a function of the drain-

current (see the Typical Operating Characteristics).

Calculating the Maximum Output Power

in UCSP

The maximum output power of the MAX8559 is limited

by the maximum power dissipation of the package. By

calculating the power dissipation of the package as a

function of the input voltage, output voltages, and out-

put currents, the maximum input voltage can be

obtained. The maximum power dissipation should not

exceed the package’s maximum power rating.

where:

(379mW for the UCSP and 1951mW for the TDFN)

consider the TDFN.

Layout Guidelines

Due to the low output noise and tight output voltage

accuracy required by most applications, careful PC

board

layout

is

required.

An

evaluation

kit

(MAX8559EVKIT) is available to speed design.

Follow these guidelines for good PC board layout:

• Keep the input and output paths short and wide if

possible, especially at the ground terminals.

• Use thick copper PC boards (2oz vs. 1oz) to

enhance thermal capabilities.

• Place output, input, and bypass capacitors as close

as possible to the IC.

• Ensure traces to BP and the BP capacitor are away

from noisy sources to ensure low output voltage noise.

Dual, 300mA, Low-Noise Linear Regulator

with Independent Shutdown in UCSP or TDFN

8

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