Applications Information

Capacitor Selection

and Regulator Stability

Use a 2.2µF capacitor on the MAX8530/MAX8531s’

inputs. Larger input capacitor values with lower ESRs

provide better supply-noise rejection and line-transient

response. To reduce noise and improve load transients,

use large-output capacitors, up to 10µF. For stable

operation over the full temperature range and with rated

maximum load currents, use a minimum of 2.2µF (or

1µF for <150mA loading for OUT1) and 1µF for OUT2.

Note that some ceramic dielectrics exhibit large capac-

itance and ESR variation with temperature. With

dielectrics such as Z5U and Y5V, it is necessary to use

4.7µF or more to ensure stability at temperatures below

-10°C. With X7R or X5R dielectrics, 2.2µF is sufficient at

all operating temperatures. These regulators are opti-

mized for ceramic capacitors. Tantalum capacitors are

not recommended.

PSRR and Operation from

Sources Other than Batteries

The MAX8530/MAX8531 is designed to deliver low

dropout voltages and low quiescent currents in battery-

powered systems. Power-supply rejection is 60dB at

low frequencies (see the Power-Supply Rejection Ratio

vs. Frequency graph in the Typical Operating Char-

acteristics).

When operating from sources other than batteries,

improve supply-noise rejection and transient response

by increasing the values of the input and output bypass

capacitors and through passive filtering techniques.

Load-Transient Considerations

The MAX8530/MAX8531 load-transient response

graphs (see the Typical Operating Characteristics)

show two components of the output response: a DC

shift in the output voltage because of the different load

currents, and the transient response. Increase the output

capacitor’s value and decrease its ESR to attenuate

transient spikes.

Input/Output (Dropout Voltage)

A regulator’s minimum input/output voltage differential

(or dropout voltage) determines the lowest usable supply

voltage. In battery-powered systems, this determines

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

MAX8530/MAX8531 use a P-channel MOSFET pass

transistor, their dropout voltage is a function of drain-to-

current (see the Typical Operating Characteristics).

Calculating the Maximum

Output Power in UCSP

The maximum output power of the MAX8530/MAX8531

can be limited by the maximum power dissipation of the

package. Obtain the maximum power dissipation by

calculating the power dissipation of the package as a

function of the input voltage, output voltage, and output

currents. The maximum power dissipation should not

exceed the package’s maximum power rating:

where:

(308mW for UCSP and 1951mW for the QFN package)

consider using the QFN package.

Dual Low-Dropout Linear Regulators

with

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