ADR121 Analog Devices, Inc., ADR121 Datasheet - Page 16

• Manufacturer Part Number: ADR121
• Description: Precision, Micropower Ldo Voltage References In Tsot
• Manufacturer: Analog Devices, Inc.

ADR121/ADR125/ADR127
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 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:
where:
T
T
P
θ
JA
D
J
A
is the junction temperature.
is the device power dissipation.
is the ambient temperature.
is the device package thermal resistance.
P
D
T
J
θ

JA
T
A
Rev. 0 | Page 16 of 20
NOTES
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 improved transient response in
the 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.