Datasheet

 2010 Microchip Technology Inc. DS22248A-page 19
MCP4901/4911/4921
4.0 GENERAL OVERVIEW
The MCP4901, MCP4911 and MCP4921 are single
channel voltage output 8-bit, 10-bit and 12-bit DAC
devices, respectively. These devices include a V
REF
input buffer, a rail-to-rail output amplifier, shutdown and
reset management circuitry. The devices use an SPI
serial communication interface and operate with a
single-supply voltage from 2.7V to 5.5V.
The DAC input coding of these devices is straight
binary. Equation 4-1 shows the DAC analog output
voltage calculation.
EQUATION 4-1: ANALOG OUTPUT
VOLTAGE (V
OUT
)
The ideal output range of each device is:
• MCP4901 (n = 8)
(a) 0V to 255/256*V
REF
when gain setting = 1x.
(b) 0V to 255/256*2*V
REF
when gain setting = 2x.
•MCP4911 (n = 10)
(a) 0V to 1023/1024*V
REF
when gain setting = 1x.
(b) 0V to 1023/1024*2*V
REF
when gain setting = 2x.
• MCP4921 (n = 12)
(a) 0V to 4095/4096*V
REF
when gain setting = 1x.
(b) 0V to 4095/4096*2*V
REF
when gain setting = 2x.
1 LSb is the ideal voltage difference between two
successive codes. Table 4-1 illustrates the LSb
calculation of each device.
4.1 DC Accuracy
4.1.1 INL ACCURACY
Integral Non-Linearity (INL) error is the maximum
deviation between an actual code transition point and
its corresponding ideal transition point, after offset and
gain errors have been removed. The two endpoints
(from 0x000 and 0xFFF) method is used for the calcu-
lation. Figure 4-1 shows the details.
A positive INL error represents transition(s) later than
ideal. A negative INL error represents transition(s) ear-
lier than ideal.
FIGURE 4-1: Example for INL Error.
4.1.2 DNL ACCURACY
A Differential Non-Linearity (DNL) error is the measure
of variations in code widths from the ideal code width.
A DNL error of zero indicates that every code is exactly
1 LSB wide.
Note: See the output swing voltage specification
in Section 1.0 “Electrical Characteris-
tics”.
V
OUT
V
REF
D
n
 
2
n
-------------------------------G=
Where:
V
REF
=EXternal voltage reference
D
n
= DAC input code
G=
=
=
Gain Selection
2 for <GA
> bit = 0
1 for <GA
> bit = 1
n=
=
=
=
DAC Resolution
8 for MCP4901
10 for MCP4911
12 for MCP4912
TABLE 4-1: LSb OF EACH DEVICE
Device
Gain
Selection
LSb Size
MCP4901
(n = 8)
1x V
REF
/256
2x (2*V
REF
)/256
MCP4911
(n = 10)
1x V
REF
/1024
2x (2*V
REF
)/1024
MCP4921
(n = 12)
1x V
REF
/4096
2x (2*V
REF
)/4096
where V
REF
is the external voltage reference.
111
110
101
100
011
010
001
000
Digital
Input
Code
Actual
Transfer
Function
INL < 0
Ideal Transfer
Function
INL < 0
DAC Output