ADR360/ADR361/ADR363/ADR364/ADR365/ADR366

Rev. A | Page 16 of 20

THEORY OF OPERATION

Band gap references are the high performance solution for low

supply voltage and low power voltage reference applications,

and the ADR36x family is no exception. The uniqueness of

these products lies in their architecture. The ideal zero TC band

gap voltage is referenced to the output not to ground (see

Figure 32). Therefore, if noise exists on the ground line, it is

PNP pair Q53 and Q52 running at unequal current densities.

which is amplified by a ratio of

R54

R59

2×

produces the stable band gap voltage.

Reduction in the band gap curvature is performed by the ratio

of Resistor R44 and Resistor R59, one of which is linearly

temperature dependent. Precision laser trimming and other

patented circuit techniques are used to further enhance the drift

performance.

R60

Q53

R54

R61

R53

Q52

R58

R59

R44

R50

30kΩ

Q2

R101

Q61

R100

Q60

Q1

R48

R49

62kΩ

TRIM

Figure 32. Simplified Schematic

DEVICE POWER DISSIPATION CONSIDERATIONS

The ADR36x family is capable of delivering load currents to

5 mA with an input voltage ranging from 2.348 V (ADR360

only) to 18 V. When this device is used in applications with

large input voltages, care should be taken to avoid exceeding the

specified maximum power dissipation or junction temperature

because it 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

T

T

P

−

=

is the device package thermal resistance.

INPUT CAPACITOR

Input capacitors are not required on the ADR36x. 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 improves transient response in

applications where the supply suddenly changes. An additional

0.1 μF capacitor in parallel also helps reduce noise from the supply.

OUTPUT CAPACITOR

The ADR36x does not require output capacitors for stability

under any load condition. An output capacitor, typically 0.1 μF,

filters out any low level noise voltage and does not affect the

operation of the part. On the other hand, the load transient

response can improve with an additional 1 μF to 10 μF output

capacitor in parallel. A capacitor here acts as a source of stored

energy for a sudden increase in load current. The only

parameter that degrades by adding an output capacitor is the

turn-on time. The degradation depends on the size of the

capacitor chosen.