Техническая Спецификация для Microchip Technology MCP4728EV
MCP4728
DS22187E-page 48
© 2010 Microchip Technology Inc.
FIGURE 6-2:
DNL Accuracy.
6.5
Offset Error
Offset error (see
) is the deviation from zero
voltage output when the digital input code is zero (zero
scale voltage). This error affects all codes by the same
amount. For the MCP4728 device, the offset error is
not trimmed at the factory. However, it can be calibrated
by software in application circuits.
scale voltage). This error affects all codes by the same
amount. For the MCP4728 device, the offset error is
not trimmed at the factory. However, it can be calibrated
by software in application circuits.
FIGURE 6-3:
Offset Error.
6.6
Gain Error
Gain error (see
) is the difference between
the actual full scale output voltage from the ideal output
voltage of the DAC transfer curve. The gain error is
calculated after nullifying the offset error, or full scale
error minus the offset error.
voltage of the DAC transfer curve. The gain error is
calculated after nullifying the offset error, or full scale
error minus the offset error.
The gain error indicates how well the slope of the actual
transfer function matches the slope of the ideal transfer
function. The gain error is usually expressed as percent
of full scale range (% of FSR) or in LSB.
transfer function matches the slope of the ideal transfer
function. The gain error is usually expressed as percent
of full scale range (% of FSR) or in LSB.
For the MCP4728 device, the gain error is not
calibrated at the factory and most of the gain error is
contributed by the output buffer (op amp) saturation
near the code range beyond 4000. For applications that
need the gain error specification less than 1%
maximum, a user may consider using the DAC code
range between 100 and 4000 instead of using full code
range (code 0 to 4095). The DAC output of the code
range between 100 and 4000 is much more linear than
full scale range (0 to 4095). The gain error can be
calibrated out by using applications’ software.
calibrated at the factory and most of the gain error is
contributed by the output buffer (op amp) saturation
near the code range beyond 4000. For applications that
need the gain error specification less than 1%
maximum, a user may consider using the DAC code
range between 100 and 4000 instead of using full code
range (code 0 to 4095). The DAC output of the code
range between 100 and 4000 is much more linear than
full scale range (0 to 4095). The gain error can be
calibrated out by using applications’ software.
6.7
Full Scale Error (FSE)
Full scale error (see
) is the sum of offset
error plus gain error. It is the difference between the
ideal and measured DAC output voltage with all bits set
to one (DAC input code = FFFh).
ideal and measured DAC output voltage with all bits set
to one (DAC input code = FFFh).
EQUATION 6-4:
FIGURE 6-4:
Gain Error and Full Scale
Error.
6.8
Gain Error Drift
Gain error drift is the variation in gain error due to a
change in ambient temperature. The gain error drift is
typically expressed in ppm/°C.
change in ambient temperature. The gain error drift is
typically expressed in ppm/°C.
010
001
000
Analog
Output
Output
(LSB)
DAC Input Code
011
111
100
101
1
2
3
4
5
6
0
7
DNL = 2 LSB
DNL = 0.5 LSB
110
Ideal Transfer Function
Actual Transfer Function
Analog
Output
Ideal Transfer Function
Actual Transfer Function
DAC Input Code
0
Offset
Error
FSE
V
OUT
V
Ide al
–
(
)
LSB
---------------------------------------
=
Where:
FSE is expressed in LSB.
V
Ideal
=
(V
REF
) (1 - 2
-n
) - Offset Voltage (V
OS
)
V
REF
=
Voltage Reference
Analog
Output
Output
Actual Transfer Function
Actual Transfer Function
DAC Input Code
0
Gain Error
Ideal Transfer Function
after Offset Error is removed
Full Scale
Error