Not Recommended For New Designs
the line (Figure 1) about the bipolar zero point and offset
DISCUSSION OF
SPECIFICATIONS
The PCM54 and PCM55 are specified to provide critical
performance criteria for a wide variety of applications. The
most critical specifications for a D/A converter in audio
applications are total harmonic distortion, differential linear-
ity error, bipolar zero error, parameter shifts with time and
temperature, and settling time effects on accuracy.
drift shifts the line left or right over the operating tempera-
ture range. Most of the offset and gain drift with temperature
or time is due to the drift of the internal reference zener
diode. The converter is designed so that these drifts are in
opposite directions. This way, the bipolar zero voltage is
virtually unaffected by variations in the reference voltage.
DIGITAL INPUT CODES
The PCM54 and PCM55 accept complementary digital
input codes in any of three binary formats (CSB, unipolar; or
COB, bipolar; or CTC, Complementary Two’s Comple-
ment, bipolar). See Table II.
The PCM54 and PCM55 are factory-trimmed and tested for
all critical key specifications.
The accuracy of a D/A converter is described by the transfer
function shown in Figure 1. Digital input to analog output
relationship is shown in Table I. The errors in the D/A
converter are combinations of analog errors due to the linear
circuitry, matching and tracking properties of the ladder and
scaling networks, power supply rejection, and reference
errors. In summary, these errors consist of initial errors
including gain, offset, linearity, differential linearity, and
power supply sensitivity. Gain drift over temperature rotates
ANALOG OUTPUT
Digital
Input
Codes
Complementary
Straight Binary
(CSB)
Complementary
Offset Binary
(COB)
Complementary
Two’s Complement
(CTS)(1)
0000H
7FFFH
8000H
+Full Scale
+1/2 Full Scale
+1/2 Full Scale
–1LSB
+Full Scale
Bipolar Zero
–1LSB
–1LSB
–Full Scale
+Full Scale
FFFFH
Zero
–Full Scale
Bipolar Zero
NOTE: (1) Invert the MSB of the COB code with an external inverter to obtain
CTC code.
0000…0000
Gain
TABLE II. Digital Input Codes.
Drift
0000…0001
0111…1101
0111…1110
0111…1111
1000…0000
1000…0001
1111…1110
1111…1111
All Bits
On
BIPOLAR ZERO ERROR
Initial Bipolar Zero (BPZ) error (Bit 1 “ON” and all other
bits “OFF”) is the deviation from 0V out and is factory-
trimmed to typically ±10mV at +25°C.
Bipolar
Zero
Offset
Drift
DIFFERENTIAL LINEARITY ERROR
Differential Linearity Error (DLE) is the deviation from an
ideal 1LSB change from one adjacent output state to the
next. DLE is important in audio applications because exces-
sive DLE at bipolar zero (at the “major carry”) can result in
audible crossover distortion for low level output signals.
Initial DLE on the PCM54 and PCM55 is factory-trimmed
to typically ±0.001% of FSR. This error is adjustable to zero
using the circuit shown in the connection diagram (PCM54
only).
(+FSR/2) –1LSB
Analog Output
* See Table I for digital code definitions.
–FSR/2
FIGURE 1. Input vs Output for an Ideal Bipolar D/A
Converter.
VOLTAGE OUTPUT MODE
Analog Output
Unipolar(1)
Bipolar
15-Bit
Digital Input Code
16-Bit
15-Bit
14-Bit
16-Bit
14-Bit
One LSB
0000H
FFFFH
(µV)
(V)
(V)
91.6
+5.99991
0
183
+5.99982
0
366
+5.99963
0
91.6
+2.99991
–3.0000
183
+2.99982
–3.0000
366
+2.99963
–3.0000
CURRENT OUTPUT MODE
Analog Output
Unipolar
Bipolar
15-Bit
Digital Input Code
16-Bit
15-Bit
14-Bit
16-Bit
14-Bit
One LSB
0000H
FFFFH
(µA)
(mA)
(mA)
0.031
–1.99997
0
0.061
–1.99994
0
0.122
–1.99988
0
0.031
–0.99997
+1.00000
0.061
–0.99994
+1.00000
0.122
–0.99988
+1.00000
NOTE: (1) +VCC must be at least +8.5VDC to allow output to swing to +6.0VDC.
TABLE I. Digital Input to Analog Output Relationship.
®
4
PCM54/55
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