ADR121AUJZ-R21 datasheet(16/20 Pages) AD

16 / 20 page

ADR121/ADR125/ADR127

Rev. B | Page 16 of 20

THEORY OF OPERATION

The ADR12x band gap references are the high performance

solution for low supply voltage and low power applications.

The uniqueness of these products lies in their architecture.

POWER DISSIPATION CONSIDERATIONS

The ADR12x family is capable of delivering load currents up to

5 mA with an input range from 3.0 V to 18 V. When this device

is used in applications with large input voltages, care must be

taken to avoid exceeding the specified maximum power

dissipation or junction temperature because this could result

in premature device failure.

Use the following formula to calculate a device’s maximum

junction temperature or dissipation:

−

(4)

where:

TJ is the junction temperature.

TA is the ambient temperature.

PD is the device power dissipation.

θJA is the device package thermal resistance.

INPUT CAPACITOR

Input capacitors are not required on the ADR12x. There is no

limit for the value of the capacitor used on the input, but a 1 μF

to 10 μF capacitor on the input may improve transient response

in applications where there is a sudden supply change. An

additional 0.1 μF capacitor in parallel also helps reduce noise

from the supply.

OUTPUT CAPACITOR

The ADR12x requires a small 0.1 μF capacitor for stability.

Additional 0.1 μF to 10 μF capacitance in parallel can improve

load transient response. This acts as a source of stored energy

for a sudden increase in load current. The only parameter

affected with the additional capacitance is turn-on time.

ADR121AUJZ-R21 Folha de dados(PDF) 16 Page - Analog Devices