6

5/15/00

SPT5400

The relationship between the reference, AGNDxx and

output voltage is shown in table V.

Table V – Relationship between Reference, AGNDxx and Output

POSITIVE

BIPOLAR OPERATION

UNIPOLAR OPERATION

PARAMETER

(AGNDxx = 0 V)

(AGND = REFxx/2)

CUSTOM OPERATION

Bipolar Zero Level or Unipolar Mid-Scale

AGNDxx = 0 V

AGNDxx = REFxx/2

AGNDxx

(Code = 1000000000000)

Differential Reference Voltage (VDR)

REFxx

REFxx/2

REF – AGNDxx

Negative Full-Scale Output (Code = All 0s)

–REFxx

0 V

AGNDxx – VDR

Positive Full-Scale Output (Code = All 1s)

(4095/4096)(REFxx)

(8191/8192)(REFxx)

AGNDxx + (4095/4096)(VDR)

LSB Weight

(REFxx/4096)

(REFxx/8192)

(VDR/4096)

((D/4096)–1)(REFxx)

(D/8192)(REFxx)

AGNDxx + ((D/4096)–1)(VDR)

(D, 0 to 8191)

Figure 2 – Typical Interface Circuit (shown for unipolar operation)

R

+

–

R

–

C2

C2

AGNDxx

1 k

Ω 1 kΩ

+

REF

FB

D12

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0 (LSB)

GND

C1

+A5 V

C1

-A5 V

CMOS/TTL Control Source

For Bipolar Operation

AGNDxx

REFxx

C2

SPT5400

Notes

R = 22

Ω

C1 = 1.0

µF

C2 = 0.1

µF

FB = Ferrite Bead

R

R