SP9602DS/02

SP9602 Dual, 12-Bit, Low Power Voltage Output D/A Converter

© Copyright 1999 Sipex Corporation

7

Figure 2. Transfer Function

calibrate a circuit, by taking full scale or zero scale

readings for both DAC’s; Figure 3, bottom.

Zeroing DAC Outputs

While keeping XFER pin high, the DAC outputs can

be set to zero volts two different ways. The first

involvestheCLRandWR2pins. Innormaloperation,

the CLR pin is tied high, thus, disabling the clear

function. By cycling WR2 and CLR through "1"—

"0"—"1" sequence, a digital code of 1000 0000 0000

iswrittentobothDACregisters,producingahalfscale

output or zero volts. The second utilizes the built in

power-on-reset. Using this feature, the SP9602 can

be configured such that during power-up, the second

register will be digitally “zeroed”, producing a zero

volt output at each of the DAC outputs. This is

achievedbypoweringtheunitupwithXFERinahigh

state. Thus,withnoexternalcircuitry,theSP9602can

be powered up with the analog outputs at a known,

zero volt output level.

Temporarily Forcing

Both DAC Outputs to OV

Set WRI=1, CS=1, WR2=0, XFER=0. The DAC

registerscanbetemporarilyforcedto100000000000

bybringingtheCLRpinlow.ThiswillcausetheDAC

outputs to 0V, while the CLR pin remains low. When

the CLR pin is brought back high, the digital code at

the DAC registers will again appear at the DAC's

digital inputs, and the analog outputs will return to

their previous values.

–

+

D

D

2048

(

)

D

4,096

A

CS

WR1

B1/B2

WR2

XFER

CLR

FUNCTION

0

1

1

X

X

Address DAC 1 and load input register

0

0

1

X

X

Address DAC 1 and load 4 LSBs

1

1

1

X

X

Address DAC 2 and load input register

1

0

1

X

X

Address DAC 2 and load 4 LSBs

X

**

**

X

1

Transfer data from input registers to DAC registers

X

1

1

X

0

0

Temporarily force both DAC output voltages to

OV, while CLR is low.

X

X

X

X

1

Sets all DAC output voltages to 0V

X

1

XXXXX

Invalid state with any other control line active

X

X

1

XXXX

Invalid state with any other control line active

X = Don’t care; ** = Don’t care; however, CS and WR1 = 1 will inhibit changes to the input registers.