LM1086RS 参数 Datasheet PDF下载

1.5A L.D.O. VOLTAGE REGULATOR (Adjustable & Fixed)

APPLICATION INFORMATION

LM1086

The LM1086 series of adjustable and fixed regulators are easy to use and have all the protection

features expected in high performance voltage regulators : short circuit protection and thermal

shut-down. Pin compatible with older three terminal adjustable regulators, these devices offer the

advantage of a lower dropout voltage, more precies reference tolerance and improved reference

stability with temperature.

STABILITY

The circuit design used in the LM1086 series requires the use of an output capacitor as part of

the device frequency compensation.

The addition of 150uF aluminum electrolytic or a 22uF solid tantalum on the output will ensure

stability for all operating conditions. When the adjustment terminal is bypassed with a capacitor to

improve the ripple rejection, the requirement for an output capacitor increases. The value of 22uF

tantalum or 150uF aluminum covers all cases of bypassing the adjustment terminal. Without

bypassing the adjustment terminal smaller capacitors can be used with equally good results.

To ensure good transient response with heavy load current changes capacitor values on the

order of 100uF are used in the output of many regulators. To further improve stability and transient

response of these devices larger values of output capacitor can be used.

PROTECTION DIODES

Unlike older regulators, the LM1086 family does not need any

protection diodies between the adjustment pin and the output

and from the output tu the input to prevent over-stressing the die.

Internal resistors are limiting the internal current paths on the

LM1086 adjustment pin, therfore even with capacitors on the

adjustment pin no protection diode is needed to ensure device

safety under short-circuit conditions.

LM1086

Diodes between the input and output are not usually needed.

Microsecond surge currents of 50A to 100A can be handled by the internal diode between the

input and output pins of the device. In norminal operations it is difficult to get those values of

surge currents even with the use of large output capacitances. If high value output capacitors are

used, such as 1000uF to 5000uF and the input pin is instantaneously shorted to ground, damage

can occur. Adiode from output to input is recommended, when a crowbar circuit at the input of the

LM1086 is used. Normal power supply cycling or even plugging and unplugging in the system will

not generate current large enough to do any damage.

The adjustment pin can be driven on a transient basis ±25V, with respect to the output without

any device degradation. As with any IC regulator, none the protection circuitry will be functional and

the internal transistors will break diwn if the maximum inout to output voltage differential is exceeded

HTC

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