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-
sured at the Major Carry (FFFF
HEX
to 0000
HEX
, and 0000
HEX
to FFFF
HEX
: BTC codes), the input transition at which
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
amplitude at sampling rate f
S
.
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
sampling rate, f
S
.
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
possible switches change state—from 7FFF
HEX
to 8000
HEX
.
7
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
configuration, a digital input of 7FFF
HEX
gives a plus full
scale output, 8000
HEX
gives a minus full scale output, and
0000
HEX
gives bipolar zero 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.
®
DAC712
BURR-BROWN [ BURR-BROWN CORPORATION ]
