ADR360AUJZ-R2 datasheet(16/20 Pages) AD

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ADR360/ADR361/ADR363/ADR364/ADR365/ADR366

Rev. D | 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

greatly attenuated on VOUT. The band gap cell consists of the

PNP pair Q53 and Q52 running at unequal current densities.

The difference in VBE results in a voltage with a positive TC,

which is amplified by a ratio of

R54

R59

This PTAT voltage, combined with the VBE of Q53 and Q52,

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

30k

Ω

R101

Q61

R100

Q60

R48

R49

62k

Ω

VOUT (FORCE)

VOUT (SENSE)

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 may result in premature device failure. Use the

following formula to calculate a device’s maximum junction

temperature or dissipation:

−

where:

TJ and TA are the junction and ambient temperatures, respectively.

PD is the device power dissipation.

θJA 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 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 placed

in parallel with the 0.1 μF capacitor. The additional capacitor

acts as a source of stored energy for a sudden increase in load

current, and the only parameter that degrades is the turn-on

time. The amount of degradation depends on the size of the

capacitor chosen.

ADR360AUJZ-R2 Datasheet(PDF) 16 Page - Analog Devices

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