DAC8222

–7–

REV. C

Figure 18. Burn-In Circuit

PARAMETER DEFINITIONS

RESOLUTION (n)

The resolution of a DAC is the number of states (2

the full-scale range (FSR) is divided (or resolved); where n is

equal to the number of bits.

RELATIVE ACCURACY (INL)

Relative accuracy, or integral nonlinearity, is the maximum de-

viation of the analog output (from the ideal) from a straight line

drawn between the end points. It is expressed in terms of least

significant bit (LSB), or as a percent of full scale.

DIFFERENTIAL NONLINEARITY (DNL)

Differential nonlinearity is the worst case deviation of any adja-

cent analog output from the ideal 1 LSB step size. The devia-

tion of the actual “step size” from the ideal step size of 1 LSB is

called the differential nonlinearity error or DNL. DACs with

DNL greater than

±1 LSB may be nonmonotonic ±1/2 LSB

INL guarantees monotonicity and

±1 LSB maximum DNL.

Gain error is the difference between the actual and the ideal

analog output range, expressed as a percent of full-scale or in

terms of LSB value. It is the deviation in slope of the DAC

transfer characteristic from ideal.

See Orientation in Digital-to-Analog Converters Section of the

current data book, for additional parameter definitions.

GENERAL CIRCUIT DESCRIPTION

CONVERTER SECTION

The DAC8222 contains four 12-bit registers (two input regis-

ters and two DAC registers), two highly stable thin-film R-2R

resistor ladder networks, and interface control logic circuitry.

Also included are 24 single-pole, double-throw, NMOS transis-

tor current switches.

Figure 19. Simplified Single DAC Circuit Configuration.

(Switches Are Shown for All Digital Inputs at Zero)

Figure 20. N-Channel Current Steering Switch

Figure 19 shows a simplified circuit for the R-2R ladder network

and transistor switches for one DAC. R is typically 11 k

Ω. The

transistor switches are binarily scaled in size to maintain a con-

stant voltage drop across each switch. Figure 20 shows a single

NMOS transistor switch.

AGND by the N-channel MOS transistor switches. The selec-

code. It is important to note here that the voltage difference