EVAL-ADUC7026QSP Analog Devices Inc, EVAL-ADUC7026QSP Datasheet - Page 43

• Manufacturer Part Number: EVAL-ADUC7026QSP
• Description: KIT DEV FOR ADUC7026/7027
• Manufacturer: Analog Devices Inc

Specifications of EVAL-ADUC7026QSP

• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Table 18. V
AV
3.3 V
3.0 V
CALIBRATION
By default, the factory-set values written to the ADC offset
(ADCOF) and gain coefficient registers (ADCGN) yield
optimum performance in terms of end-point errors and
linearity for standalone operation of the part (see the
Specifications section), If system calibration is required, it is
possible to modify the default offset and gain coefficients to
improve end-point errors, but note that any modification to the
factory-set ADCOF and ADCGN values can degrade ADC
linearity performance.
For system offset error correction, the ADC channel input stage
must be tied to AGND. A continuous software ADC conversion
loop must be implemented by modifying the value in ADCOF until
the ADC result (ADCDAT) reads code 0 to 1. If the ADCDAT
value is greater than 1, ADCOF should be decremented until
ADCDAT reads 0 to 1. Offset error correction is done digitally
and has a resolution of 0.25 LSB and a range of ±3.125% of V
For system gain error correction, the ADC channel input stage
must be tied to V
loop must be implemented to modify the value in ADCGN
until the ADC result (ADCDAT) reads code 4094 to 4095. If the
ADCDAT value is less than 4094, ADCGN should be
incremented until ADCDAT reads 4094 to 4095. Similar to the
offset calibration, the gain calibration resolution is 0.25 LSB
with a range of ±3% of V
TEMPERATURE SENSOR
The ADuC7019/20/21/22/24/25/26/27/28 provide voltage
output from on-chip band gap references proportional to
absolute temperature. This voltage output can also be routed
through the front-end ADC multiplexer (effectively an additional
ADC channel input) facilitating an internal temperature sensor
channel, measuring die temperature to an accuracy of ±3°C.
The following is an example routine showing how to use the
internal temperature sensor:
int main(void)
{
float a = 0;
Sensor as an // input to the ADC
DD
short b;
ADCCON = 0x20;
delay(2000);
ADCCP = 0x10; // Select Temperature
V
2.5 V
2.048 V
1.25 V
2.5 V
2.048 V
1.25 V
REF
CM
Ranges
REF
V
1.25 V
1.024 V
0.75 V
1.25 V
1.024 V
0.75 V
. A continuous software ADC conversion
CM
Min
REF
.
V
2.05 V
2.276 V
2.55 V
1.75 V
1.976 V
2.25 V
CM
// power-on the ADC
Max
Signal Peak-to-Peak
2.5 V
2.048 V
1.25 V
2.5 V
2.048 V
1.25 V
Rev. B | Page 43 of 92
REF
.
reference // to Vref pin
the formula:
Voltage) / 1.3)
oC\n",b);
}
BAND GAP REFERENCE
Each ADuC7019/20/21/22/24/25/26/27/28 provides an on-chip
band gap reference of 2.5 V, which can be used for the ADC and
DAC. This internal reference also appears on the V
using the internal reference, a 0.47 μF capacitor must be connected
from the external V
response during ADC conversions. This reference can also be
connected to an external pin (V
other circuits in the system. An external buffer is required because
of the low drive capability of the V
option also allows an external reference input on the V
Note that it is not possible to disable the internal reference.
Therefore, the external reference source must be capable of
overdriving the internal reference source.
REFCON Register
Name
REFCON
The band gap reference interface consists of an 8-bit MMR
REFCON described in Table 19.
Table 19. REFCON MMR Bit Designations
Bit
7:1
0
ADuC7019/20/21/22/24/25/26/27/28
REFCON = 0x01; // connect internal 2.5V
ADCCON = 0xE4; // continuous conversion
while(1)
{
// wait for end of conversion
// To calculate temperature in °C, use
// ((Temperature = 0x525 - Sensor
}
return 0;
Description
Reserved.
Internal Reference Output Enable. Set by user to
connect the internal 2.5 V reference to the V
The reference can be used for external component
but needs to be buffered. Cleared by user to
disconnect the reference from the V
Address
0xFFFF048C
while (!ADCSTA){};
b = (ADCDAT >> 16);
a = 0x525 - b;
a /= 1.3;
b = floor(a);
printf("Temperature: %d
REF
pin to AGND to ensure stability and fast
REF
Default Value
0x00
REF
) and used as a reference for
output. A programmable
REF
pin.
REF
pin. When
REF
REF
Access
R/W
pin.
pin.