ADUC7126 Analog Devices, ADUC7126 Datasheet - Page 42

• Manufacturer Part Number: ADUC7126
• Description: Precision Analog Microcontroller, 12-Bit Analog I/O, Large Memory, ARM7TDMI MCU with Enhanced IRQ Handler
• Manufacturer: Analog Devices

Specifications of ADUC7126

• Mcu Core: ARM7 TDMI
• Mcu Speed (mips): 40
• Gpio Pins: 40
• Adc # Channels: 16
• Other: PWM

ADuC7124/ADuC7126
CALIBRATION
By default, the factory-set values written to the ADC offset
(ADCOF) and gain coefficient registers (ADCGN) yield opti-
mum 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 Code 1. If the
ADCDAT value is greater than 1, ADCOF should be decremented
until ADCDAT reads Code 0 to Code 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 Code 4095. If the
ADCDAT value is less than 4094, ADCGN should be incremented
until ADCDAT reads Code 4094 to Code 4095. Similar to the
offset calibration, the gain calibration resolution is 0.25 LSB
with a range of ±3% of V
TEMPERATURE SENSOR
The ADuC7124/ADuC7126 provide voltage outputs from an
on-chip band gap reference that is 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.
An ADC temperature sensor conversion differs from a standard
ADC voltage. The ADC performance specifications do not
apply to the temperature sensor.
Chopping of the internal amplifier must be enabled using the
TSCON register. To enable this mode, the user must set Bit 0 of
TSCON. The user must also take two consecutive ADC readings
and average them in this mode.
The ADCCON register must be configured to 0x37A3.
To calculate die temperature, use the following formula:
where:
T is the temperature result.
T
For the ADuC7124, V
V
in Table 1.
V
conversions.
REF
TREF
ADC
= 25°C.
T – T
is the average ADC result from two consecutive
= 1.392 V, which corresponds to T
REF
= (V
REF
.
REF
ADC
. A continuous software ADC conversion
– V
TREF
REF
TREF
= 1.415 V and for the ADuC7126,
.
) × K
REF
= 25°C, as described
Rev. B | Page 42 of 104
K is the gain of the ADC in temperature sensor mode as
determined by characterization data. K = 0.2555°C/mV
for ADuC7124. K = 0.2212°C/mV for ADuC7126. This
corresponds to the 1/voltage temperature coefficient
specification from Table 1.
Using the default values from Table 1 and without any
calibration, this equation becomes
where V
For better accuracy, the user should perform a single point
calibration at a controlled temperature value.
For the calculation with no calibration, use 25°C and 1415 mV
for the ADuC7124 and 1392mV for the ADuC7126. The idea
of a single point calibration is to use other known (T
values to replace the common T = 25°C and 1415 mV for the
ADuC7124 and 1392 mV for the ADuC7126 for every part.
For some users, it is not possible to obtain such a known pair.
For such cases, the ADuC7124/ADuC7126 comes with a single
point calibration value loaded in the TEMPREF register. For
more details on this register, see Table 35. During production
testing of the ADuC7124/ADuC7126, the TEMPREF register is
loaded with an offset adjustment factor. Each part has a
different value in the TEMPREF register. Using this single point
calibration, the same formula is still used.
where:
T
V
TSCON Register
Name:
Address:
Default Value:
Access:
Table 34. TSCON MMR Bit Descriptions
Bit
[7:1]
0
REF
TREF
= 25°C but is not guaranteed.
T − 25°C = (V
T − 25°C = (V
T – T
can be calculated using the TEMPREF register.
ADC
REF
Description
Reserved.
Temperature sensor chop enable bit. This bit must
be set.
This bit is set to 1 to enable chopping of the internal
amplifier to the ADC.
This bit is cleared to disable chopping. This results in
incorrect temperature sensor readings.
This bit is cleared by default.
is in mV.
= (V
ADC
ADC
ADC
TSCON
0xFFFF0544
0x00
Read/write
– V
− 1415) × 0.2555 for ADuC7124
−1392) × 0.2212 for ADuC7126
TREF
) × K
REF
, V
TREF
)