MAX8885EUK25 Просмотр технического описания (PDF) - Maxim Integrated

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MAX8885EUK25

150mA, Low-Dropout Linear Regulator with Power-OK Output

Maxim Integrated 

150mA, Low-Dropout Linear Regulator

with Power-OK Output

IN

SHDN

REVERSE

BATTERY

PROTECTION

MAX8885

SHUTDOWN

LOGIC

ERROR

AMP

MOS DRIVER

WITH ILIMIT

P

OUT

POK

THERMAL

1.25V

95%

POK

SENSOR

REF

REF

GND

Figure 1. Functional Diagram

thermal sensor will turn the pass transistor on again

after the IC’s junction temperature cools by 20°C,

resulting in a pulsed output during continuous thermal-

overload conditions.

Thermal-overload protection is designed to protect the

MAX8885 in the event of fault conditions. For continuous

operation, do not exceed the absolute maximum

junction-temperature rating of TJ = +150°C.

Operating Region and Power Dissipation

The MAX8885’s maximum power dissipation depends

on the thermal resistance of the case and circuit board,

the temperature difference between the die junction

and ambient air, and the rate of air flow. The power dis-

sipation across the device is P = IOUT (VIN - VOUT). The

maximum power dissipation is:

PMAX = (TJ - TA) / ( θJB + θBA)

where TJ - TA is the temperature difference between the

MAX8885 die junction and the surrounding air; θJB (or

θJC) is the thermal resistance of the package; and θBA

is the thermal resistance through the printed circuit

board, copper traces, and other materials to the sur-

rounding air.

The MAX8885’s GND pin performs the dual function of

providing an electrical connection to system ground

and channeling heat away. Connect GND to the system

ground using a large pad or ground plane.

Reverse-Battery Protection

The MAX8885 has a unique protection scheme that lim-

its the reverse supply current to 1mA when either VIN or

V SHDN falls below ground. The circuitry monitors the

polarity of these two pins and disconnects the internal

circuitry and parasitic diodes when the battery is

reversed. This feature prevents device damage.

Applications Information

Capacitor Selection and

Regulator Stability

The MAX8885 is designed primarily for applications

using low-cost, high-ESR output capacitors such as

small case-size tantalum electrolytic capacitors. These

capacitors have ESR that can extend as high as 10Ω,

and their capacitance and ESR can vary widely over

their operating temperature range. For stable operation

over the full operating range, use a 4.7µF (1µF min)

capacitor with ESR > 0.5Ω (see the Region of Stable

COUT ESR vs. Load Current graph in the Typical

Operating Characteristics). Ceramic output capacitors

should not be used with the MAX8885. For a pin-com-

patible, functionally equivalent linear regulator that is

suitable for ceramic output capacitors, refer to the

MAX8875 data sheet.

Bypass the MAX8885’s input with a 1µF or greater

capacitor to GND. Place this capacitor close to the

device (<5mm).

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