CAT522

7

Doc. No. 2004, Rev. E

Figure 3. Temporary Change in Output

same as that which had been there previously no change

in the DPP’s output is noticed. Had the value held in the

control register been different from that stored in non-

volatile memory then a change would occur at the read

cycle’s conclusion.

TEMPORARILY CHANGE OUTPUT

The CAT522 allows temporary changes in DPP’s output

to be made without disturbing the settings retained in

non-volatile memory. This feature is particularly useful

when testing for a new output setting and allows for user

adjustment of preset or default values without losing the

original factory settings.

Figure 3 shows the control and data signals needed to

effect a temporary output change. DPP wiper settings

may be changed as many times as required and can be

made to any of the two DPPs in any order or sequence.

The temporary setting(s) remain in effect long as CS

remains high. When CS returns low all two DPPs will

return to the output values stored in non-volatile memory.

When it is desired to save a new setting acquired using

this feature, the new value must be reloaded into the

DPP wiper control register prior to programming. This is

because the CAT522’s internal control circuitry discards

from the programming register the new data two clock

cycles after receiving it if no PROG signal is received.

Amplified DPP Output

APPLICATION CIRCUITS

Bipolar DPP Output

D0

D1

D2

D3

D4

D5

D6

D7

A0

A1

D0

D1

D2

D3

D4

D5

D6

D7

1

NEW DPP DATA

CURRENT DPP DATA

DO

DI

CS

PROG

DPP

OUTPUT

t

1

2

3

4

5

6

7

8

9

10

11

12

N

N+1 N+2

o

CURRENT

DPP VALUE

NON-VOLATILE

NEW

DPP VALUE

VOLATILE

CURRENT

DPP VALUE

NON-VOLATILE

RDY/BSY

MSB

LSB

1111

1111

—— (.98 V

) + .01 V

= .990 V

V

= +4.90V

1000

0000

—— (.98 V

) + .01 V

= .502 V

V

= +0.02V

0111

1111

—— (.98 V

) + .01 V

= .498 V

V

= -0.02V

0000

0001

—— (.98 V

) + .01 V

= .014 V

V

= -4.86V

0000

0000

—— (.98 V

) + .01 V

= .010 V

V

= -4.90V

REF

REF

REF

IF

V

= 5V

REF

255

255

OUT

DPP INPUT

DPP OUTPUT

ANALOG

R = R

OUTPUT

REF

REF

REF

OUT

128

255

127

255

REF

REF

REF

OUT

1

255

REF

REF

REF

OUT

REF

REF

REF

OUT

0

255

V

= 0.99 V

FS

REF

V

= 0.01 V

ZERO

REF

V

= ——— (V

- V

) + V

DPP

CODE

255

FS

ZERO

ZERO

CAT522

GND

VDD

VREFH

VREFL

CONTROL

& DATA

+

–

OP 07

VOUT

-15V

+15V

+5V

RR

I

F

V

= (1 + –––) V

OUT

DPP

RF

RI

CAT522

GND

VDD

VREFH

VREFL

CONTROL

& DATA

+

–

OP 07

V

=

(

) -V

OUT

RF

R +

i

-15V

+15V

+5V

RR

i

F

Ri

i

RF

V DPP

For R =

i

RF

V

= 2V

-V

OUT

i

DPP

Vi

VOUT