DAC7541AJP-BI BURR-BROWN [Burr-Brown Corporation], DAC7541AJP-BI Datasheet - Page 5

• Manufacturer Part Number: DAC7541AJP-BI
• Description: Low Cost 12-Bit CMOS Four-Quadrant Multiplying DIGITAL-TO-ANALOG CONVERTER
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

DISCUSSION
OF SPECIFICATIONS
RELATIVE ACCURACY
This term (also known as linearity) describes the transfer
function of analog output to digital input code. The linearity
error describes the deviation from a straight line between
zero and full scale.
DIFFERENTIAL NONLINEARITY
Differential nonlinearity is the deviation from an ideal 1LSB
change in the output, from one adjacent output state to the
next. A differential nonlinearity specification of 1.0LSB
guarantees monotonicity.
GAIN ERROR
Gain error is the difference in measure of full-scale output
versus the ideal DAC output. The ideal output for the
DAC7541A is –(4095/4096) X (V
adjusted to zero using external trims.
OUTPUT LEAKAGE CURRENT
The measure of current which appears at Out
loaded with all zeros, or at Out
all ones.
MULTIPLYING FEEDTHROUGH ERROR
This is the AC error output due to capacitive feedthrough
from V
test is performed at 10kHz.
OUTPUT CURRENT SETTLING TIME
This is the time required for the output to settle to a tolerance
of 0.5LSB of final value from a change in code of all zeros
to all ones, or all ones to all zeros.
PROPAGATION DELAY
This is the measure of the delay of the internal circuitry and
is measured as the time from a digital code change to the
point at which the output reaches 90% of final value.
DIGITAL-TO-ANALOG GLITCH IMPULSE
This is the measure of the area of the glitch energy measured
in nV-seconds. Key contributions to glitch energy are digital
word-bit timing differences, internal circuitry timing differ-
ences, and charge injected from digital logic.
MONOTONICITY
Monotonicity assures that the analog output will increase or
stay the same for increasing digital input codes. The
DAC7541A is guaranteed monotonic to 12 bits.
POWER SUPPLY REJECTION
Power supply rejection is the measure of the sensitivity of
the output (full scale) to a change in the power supply
voltage.
REF
to Out
1
with the DAC loaded with all zeros. This
2
with the DAC loaded with
REF
). Gain error may be
1
with the DAC
5
CIRCUIT DESCRIPTION
The DAC7541A is a 12-bit multiplying D/A converter
consisting of a highly stable thin-film R-2R ladder network
and 12 pairs of current steering switches on a monolithic
chip. Most applications require the addition of a voltage or
current reference and an output operational amplifier.
A simplified circuit of the DAC7541A is shown in Figure 1.
The R-2R inverted ladder binarily divides the input currents
that are switched between I
switching allows a constant current to be maintained in each
ladder leg independent of the input code.
The input resistance at V
R
is equal to value “R”). Since R
the reference terminal can be driven by a reference voltage
or a reference current, AC or DC, of positive or negative
polarity.
FIGURE 1. Simplified DAC Circuit.
EQUIVALENT CIRCUIT ANALYSIS
Figures 2 and 3 show the equivalent circuits for all digital
inputs low and high, respectively. The reference current is
switched to I
inputs are high. The I
surface and junction leakages to the substrate; the
1/4096 current source represents the constant one-bit current
drain through the ladder terminal.
DYNAMIC PERFORMANCE
Output Impedance
The output resistance, as in the case of the output capaci-
tance, is also modulated by the digital input code. The
resistance looking back into the I
anywhere between 10k
all digital inputs are low) and 7.5k
in parallel with approximately 30k
network resistance when any single bit logic is high). The
static accuracy and dynamic performance will be affected by
this modulation. The gain and phase stability of the output
LDR
V
REF
(MSB)
Bit 1
(R
S
20k
LDR
1
10k
Digital Inputs (DTL-/TTL-/CMOS-compatible)
Switches shown for digital inputs “HIGH”.
is the R/2R ladder characteristic resistance and
OUT 2
Bit 2
S
20k
2
when all inputs are low and I
10k
L
current source is the combination of
Bit 3
(the feedback resistor alone when
REF
S
OUT 1
20k
DAC7541A
3
(Figure 1) is always equal to
IN
10k
at the V
and I
OUT 1
Bit 12
(LSB)
(the feedback resistor
OUT 2
S
of the R-2R ladder
20k
12
REF
terminal may be
pin is constant,
bus lines. This
20k
OUT 1
I
I
R
when
OUT 2
OUT 1
FB
®