ADR280AKS-REEL7(RevA) データシートの表示（PDF） - Analog Devices

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ADR280AKS-REEL7
(Rev.:RevA)

1.2 V Ultralow Power High PSRR Voltage Reference

Analog Devices 

ADR280

1.2

tS

1.0

0.8

0.6

0.4

0.2

0

0

2

4

6

8 10 12 14 16 18 20

TIME (ms)

TPC 7. Settling Time

THEORY OF OPERATION

The ADR280 provides the basic core 1.2 V band gap reference.

It contains two NPN transistors, Q9 and Q17, with their emitter

areas scaled in a fixed ratio. The difference in their Vbes produces

a PTAT (proportional to absolute temperature) voltage that

cancels the CTAT (complementary to absolute temperature) Q9

Vbe voltage. As a result, a core band gap voltage that is almost a

constant 1.2 V over temperature is generated (see Figure 2). Preci-

sion laser trimming of the internal resistors and other proprietary

circuit techniques are used to enhance the initial accuracy, tem-

perature curvature, and temperature drift performance.

V+

R1

R2

R12

Q1

R3

I1

R4

Q2

Q7

Q10

R13 C1

PNP3

Q3

Q17

Q18

Q9

R7

R5

R6

Q6

Q5

R10

VOUT

R8

R11

R9

V–

Figure 2. Simplified Architecture

APPLICATIONS

The ADR280 should be decoupled with a 0.1 µF ceramic cap at

the output for optimum stability. It is also good practice to

include 0.1 µF ceramic caps at the IC supply pin. These capaci-

tors should be mounted close to their respective pins (see Figure 3).

0.1F

V+

ADR280

V–

0.1F

VOUT

Figure 3. Basic Configuration

The low supply voltage input pin V– can be elevated above

ground; a 1.2 V differential voltage can therefore be established

above V– (see Figure 4).

5V

0.1F

V+

ADR280

V–

2.5V

0.1F

VOUT

1.2V

Figure 4. Floating References

–4–

REV. A

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