AAT3236(2001) データシートの表示（PDF） - Advanced Analogic Technologies

部品番号

コンポーネント説明

一致するリスト

AAT3236
(Rev.:2001)

300mA CMOS High Performance LDO

Advanced Analogic Technologies 

AAT3236

300mA CMOS High Performance LDO

ciated with a capacitor, which includes lead resist-

ance, internal connections, size and area, material

composition and ambient temperature. Typically

capacitor ESR is measured in milliohms for ceramic

capacitors and can range to more than several ohms

for tantalum or aluminum electrolytic capacitors.

Ceramic Capacitor Materials: Ceramic capaci-

tors less than 0.1µF are typically made from NPO

or COG materials. NPO and COG materials are

typically tight tolerance very stable over tempera-

ture. Larger capacitor values are typically com-

posed of X7R, X5R, Z5U and Y5V dielectric mate-

rials. Large ceramic capacitors, typically greater

then 2.2µF are often available in the low cost Y5V

and Z5U dielectrics. These two material types are

not recommended for use with LDO regulators

since the capacitor tolerance can vary more than

±50% over the operating temperature range of the

device. A 2.2µF Y5V capacitor could be reduced to

1µF over temperature, this could cause problems

for circuit operation. X7R and X5R dielectrics are

much more desirable. The temperature tolerance

of X7R dielectric is better than ±15%.

Capacitor area is another contributor to ESR.

Capacitors which are physically large in size will

have a lower ESR when compared to a smaller sized

capacitor of equivalent material and capacitance

value. These larger devices can improve circuit

transient response when compared to an equal

value capacitor in a smaller package size.

Consult capacitor vendor data sheets carefully

when selecting capacitors for LDO regulators.

Enable Function

The AAT3236 features an LDO regulator enable /

disable function. This pin (EN) is active high and is

compatible with CMOS logic. To assure the LDO

regulator will switch on, the EN turn on control level

must be greater than 2.0 volts. The LDO regulator

will go into the disable shutdown mode when the

voltage on the EN pin falls below 0.6 volts. If the

enable function is not needed in a specific applica-

tion, it may be tied to VIN to keep the LDO regula-

tor in a continuously on state.

When the LDO regulator is in the shutdown mode,

an internal 1.5kΩ resistor is connected between

VOUT and GND. This is intended to discharge COUT

when the LDO regulator is disabled. The internal

1.5kΩ has no adverse effect on device turn on time.

3236.2001.11.0.9

Short Circuit Protection

The AAT3236 contains an internal short circuit pro-

tection circuit that will trigger when the output load

current exceeds 750mA. Under short circuit condi-

tions the output will be limited to 750mA until the

LDO regulator package power dissipation exceeds

the device thermal limit or the until the short circuit

condition is removed.

Thermal Protection

The AAT3236 has an internal thermal protection cir-

cuit which will turn on when the device die temper-

ature exceeds 150°C. The internal thermal protec-

tion circuit will actively turn off the LDO regulator

output pass device to prevent the possibility of over

temperature damage. The LDO regulator output

will remain in a shutdown state until the internal die

temperature falls back below the 150°C trip point.

The combination and interaction between the short

circuit and thermal protection systems allow the

LDO regulator to withstand indefinite short circuit

conditions without sustaining permanent damage.

No-Load Stability

The AAT3236 is designed to maintain output volt-

age regulation and stability under operational no-

load conditions. This is an important characteristic

for applications where the output current may drop

to zero.

Reverse Output to Input Voltage

Conditions and Protection

Under normal operating conditions a parasitic

diode exists between the output and input of the

LDO regulator. The input voltage should always

remain greater than the output load voltage main-

taining a reverse bias on the internal parasitic

diode. Conditions where VOUT might exceed VIN

should be avoided since this would forward bias

the internal parasitic diode and allow excessive

current flow into the VOUT pin possibly damaging

the LDO regulator.

In applications where there is a possibility of VOUT

exceeding VIN for brief amounts of time during nor-

mal operation, the use of a larger value CIN capaci-

tor is highly recommended. A larger value of CIN

with respect to COUT will effect a slower CIN decay

rate during shutdown, thus preventing VOUT from

exceeding VIN. In applications where there is a

greater danger of VOUT exceeding VIN for extended

9

Share Link: