Advanced Monolithic Systems, Inc.

6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140

AMS500

TYPICAL PERFORMANCE CHARACTERISTICS (Continued)

APPLICATION NOTES

Definition of Terms

the circuit stops to regulate against further reduction in input

voltage. Measured when the output voltage has dropped 100mV

from the nominal voltage obtained at 1V input, dropout voltage is

dependent upon load current and junction temperature.

with respect to ground.

difference between the unregulated input voltage and the

regulated output voltage for which the regulator will regulate.

the input voltage. The line regulation is measured under

conditions of low dissipation or by using low duty cycle pulse

testing such that the average chip temperature is not significantly

affected.

load current at constant chip temperature.

life-test conditions after 1000 hours with maximum rated voltage

and junction temperature.

constant load and no input ripple, measured over a specified

frequency range.

does not contribute to the positive load current. The regulator

ground lead current.

voltage to the peak-to-peak output ripple voltage at specified

frequency.

voltage for a thermal variation from room temperature to either

temperature extreme.

External capacitor

The AMS500 series require an output capacitor of 10

µF or

greater to ensure device stability. Without the capacitor the

device may oscillate

Most type of tantalum or electrolytic capacitor can be used in the

applications. A critical characteristic of the capacitors is an ESR

value of 5

Ω or less and a resonant frequency above 500kHz. The

value of this capacitor can be increased without limits.

For higher loads, the value of the capacitor should be increased,

specialy when the output voltage is set for 2.5V or less. The

AMS500 lowest fixed output voltage value is 2.0V

Typical application circuit (adjustable output)

R

2

ADJ

+

AMS500

ADJUSTABLE

GND

C1

22

µF

10µF

OUT

OFF

ON

ON/OFF

R

1

28k

V

OUT

V

IN

100k

Minimum Load

In circuits using the fixed output voltage versions, minimum load

is not required. For circuits using the adjustable device, the value

of R1 and R2 should be chosen such, that a current of

approximately 40

µA flows through the network. The reference

The output voltage can be set by the two resistors R1 and R2

using the following equation:













+

=

R1

R2

R1

V

V

REF

O

The value of R1 is recommended to be between 25k

Ω to 30 kΩ,

and the value of R2 will set the output voltage.

-40

40

80

120

25

10

Quiescent Current

TEMPERATURE (° C)

15

2

0

0

0

100

200

0

8

4

Quiescent Current

300

OUTPUT CURRENT (mA)

2

10

6

~

~

~

~

V

20

3

1

I

I

50

150

250

350

I

I

-2.5

2.5

10

5.0

17.5

0

1

2

4

5

6

7

8

10

INPUT VOLTAGE (V)

Quiescent Current

0

7.5

15

12.5

I

3

9