Low-Dropout, 300mA

Linear Regulator in µMAX

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Current Requirements

When operating the MAX8860 with an input voltage

above +5.5V, a minimum load current of 20µA is

required to maintain regulation in preset voltage mode.

When setting the output with external resistors, ensure

that the minimum current through the external feedback

resistors and load is at least 30µA. This applies only

when the input voltage exceeds +5.5V. For input volt-

ages less than +5.5V, the MAX8860 maintains regula-

tion and stability without external loading.

Applications Information

Capacitor Selection and

Regulator Stability

Typically, use a 2.2µF capacitor on the input and a

2.2µF capacitor on the output of the MAX8860.

Capacitor type is not critical, as long as it has an ESR

less than 0.5

Ω. Larger capacitor values and lower ESR

provide better supply-noise rejection and transient

response. Use higher-value capacitors (10µF) if large,

fast input or load transients are anticipated or if the

device is located several inches from the power source.

For stable operation over the full temperature range,

with load currents up to 300mA, a minimum output-

capacitor value of 2.2µF is recommended. There is no

upper limit to capacitor size. The circuit used to gener-

ate the typical operating characteristics data used

2.2µF, X7R, 16V (1206) ceramic capacitors. These

capacitors typically have an ESR of 50m

Ω.

Power-Supply Rejection and Operation

from Sources Other than Batteries

The MAX8860 is designed to deliver low dropout volt-

age and low quiescent current in battery-powered sys-

tems. Power-supply rejection is 67dB at low frequencies

and rolls off above 100kHz. At high frequencies, the out-

put capacitor is the major contributor to the rejection of

power-supply noise (see the Power-Supply Rejection

Ratio vs. Frequency graph in the Typical Operating

Characteristics).

When operating from sources other than batteries,

improve supply-noise rejection and transient response

by increasing the values of the input and output capaci-

tors, and by using passive filtering techniques (see the

supply and load-transient responses in the Typical

Operating Characteristics).

Load-Transient Considerations

The MAX8860 load-transient response graph (see

Typical Operating Characteristics) shows the output

response due to changing load current. Reduce over-

shoot by increasing the output capacitor’s value and

decreasing its ESR.

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 MAX8860

uses a P-channel MOSFET pass transistor, its dropout

Ω) multi-

plied by the load current (see Electrical Characteristics).

Chip Information

TRANSISTOR COUNT: 148