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DAC712

DISCUSSION OF

SPECIFICATIONS

LINEARITY ERROR

Linearity error is defined as the deviation of the analog

output from a straight line drawn between the end points of

the transfer characteristic.

DIFFERENTIAL LINEARITY ERROR

Differential linearity error (DLE) is the deviation from

1LSB of an output change from one adjacent state to the

next. A DLE specification of

±1/2LSB means that the output

step size can range from 1/2LSB to 3/2LSB when the digital

input code changes from one code word to the adjacent code

word. If the DLE is more positive than –1LSB, the D/A is

said to be monotonic.

MONOTONICITY

A D/A converter is monotonic if the output either increases

or remains the same for increasing digital input values.

Monotonicity of DAC712 is guaranteed over the specifica-

tion temperature range to 13, 14, 15, and 16 bits for perfor-

mance grades DAC712P/U, DAC712PB/UB, DAC712PK/

UK, and DAC712PL/UL respectively.

SETTLING TIME

Settling time is the total time (including slew time) for the

D/A output to settle to within an error band around its final

value after a change in input. Settling times are specified to

within

±0.003% of Full Scale Range (FSR) for an output

step change of 20V and 1LSB. The 1LSB change is mea-

worst-case settling time occurs.

TOTAL HARMONIC DISTORTION + NOISE

Total harmonic distortion + noise is defined as the ratio of

the square root of the sum of the squares of the values of the

harmonics and noise to the value of the fundamental fre-

quency. It is expressed in % of the fundamental frequency

SIGNAL-TO-NOISE

AND DISTORTION RATIO (SINAD)

SINAD includes all the harmonic and outstanding spurious

components in the definition of output noise power in

addition to quantizing and internal random noise power.

SINAD is expressed in dB at a specified input frequency and

DIGITAL-TO-ANALOG GLITCH IMPULSE

The amount of charge injected into the analog output from

the digital inputs when the inputs change state. It is mea-

sured at half scale at the input codes where as many as

DIGITAL FEEDTHROUGH

When the A/D is not selected, high frequency logic activity

on the digital inputs is coupled through the device and shows

up as output noise. This noise is digital feedthrough.

OPERATION

DAC712 is a monolithic integrated-circuit 16-bit D/A con-

verter complete with 16-bit D/A switches and ladder net-

work, voltage reference, output amplifier and microproces-

sor bus interface.

INTERFACE LOGIC

DAC712 has double-buffered data latches. The input data

latch holds a 16-bit data word before loading it into the

second latch, the D/A latch. This double-buffered organiza-

tion permits simultaneous update of several D/A converters.

All digital control inputs are active low. Refer to block

diagram of Figure 1.

All latches are level-triggered. Data present when the enable

inputs are logic “0” will enter the latch. When the enable

inputs return to logic “1”, the data is latched.

The CLR input resets both the input latch and the D/A latch

to give a bipolar zero output.

LOGIC INPUT COMPATIBILITY

DAC712 digital inputs are TTL compatible (1.4V switching

level) with low leakage, high impedance inputs. Thus the

inputs are suitable for being driven by any type of 5V logic

such as 5V CMOS logic. An equivalent circuit of a digital

input is shown in Figure 2.

Data inputs will float to logic “0” and control inputs will

float to logic “0” if left unconnected. It is recommended that

any unused inputs be connected to DCOM to improve noise

immunity.

Digital inputs remain high impedance when power is off.

INPUT CODING

DAC712 is designed to accept positive-true binary two’s

complement (BTC) input codes which are compatible with

bipolar analog output operation. For bipolar analog output

INTERNAL REFERENCE

DAC712 contains a +10V reference.

The reference output may be used to drive external loads,

sourcing up to 2mA. The load current should be constant,

otherwise the gain and bipolar offset of the converter will

vary.