Datasheet

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:
JA
A
J
D
θ
TT
P
−
= (4)
where:
T
J
is the junction temperature.
T
A
is the ambient temperature.
P
D
is the device power dissipation.
θ
JA
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.