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AMS3107

500mA LOW DROPOUT VOLTAGE REGULATOR

Advanced Monolithic Systems Inc 

AMS3107

TYPICAL PERFORMANCE CHARACTERISTICS (Continued)

Operation During Load Dump

70

60

50

40

30

20

τ =150 ms

10

0

5

~~

CO= 100µF

~~

4

RL= 500Ω

3

2

1

0

-100 0 100 200 300 400 500

TIME (ms)

Reference Voltage

1.30

1.28 AMS3107 ADJUSTABLE

1.26

1.24

1.22

1.20

1.18

1.16

1.14

1.12

1.10

0

3 6 9 12 15 18 21 24

OUTPUT VOLTAGE (V)

APPLICATION NOTES

Definition of Terms

Dropout Voltage: The input-output voltage differential at which

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.

Input Voltage: The DC voltage applied to the input terminal with

respect to ground. Input-Output Differential: The voltage

difference between the unregulated input voltage and the regulated

output voltage for which the regulator will regulate.

Line Regulation: The change in output voltage for a change in

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 Regulation: The change in output voltage for a change in

load current at constant chip temperature.

Long term stability: Output voltage stability under accelerated

life-test conditions after 1000 hours with maximum rated voltage

and junction temperature.

Output Noise Voltage: The rms AC voltage at the output, with

constant load and no input ripple, measured over a specified

frequency range.

Quiescent Current: That part of the positive input current that

does not contribute to the positive load current. The regulator

ground lead current.

Ripple Rejection: The ratio of the peak-to –peak input ripple

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

frequency.

Temperature Stability of VO: The percentage change in output

voltage for a thermal variation from room temperature to either

temperature extreme.

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

applications. A critical characteristic of the capacitors is an ESR

value of 5Ω 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

AMS3107 lowest fixed output voltage value is 2.0V.

Typical application circuit (adjustable output)

VIN

10µF

100k

OUT

OFF

ON/OFF AMS3107

R1

ADJUSTABLE

28k

ON

ADJ

+

GND

R2

VOUT

C1

22µF

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 40µA flows through the network. The reference

voltage (1.235V) is measured between the adjust pin and VOUT.

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

using the following equation:

External capacitor

The AMS3107 series require an output capacitor of 10µF or

greater to ensure device stability. Without the capacitor the device

may oscillate.

VO = VREF ⎜⎛ R1 + R2 ⎟⎞

⎝ R1 ⎠

Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722

Fax (925) 443-0723

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