PIC18F87J72-I/PT Microchip Technology, PIC18F87J72-I/PT Datasheet - Page 441

• Manufacturer Part Number: PIC18F87J72-I/PT
• Description: IC PIC MCU 8BIT 14KB FLSH 80TQFP
• Manufacturer: Microchip Technology
• Series: PIC® 18Fr

Specifications of PIC18F87J72-I/PT

• Program Memory Type: FLASH
• Program Memory Size: 128KB (64K x 16)
• Package / Case: 80-TQFP
• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 48MHz
• Connectivity: I²C, LIN, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, LCD, LVD, POR, PWM, WDT
• Number Of I /o: 51
• Ram Size: 3.8K x 8
• Voltage - Supply (vcc/vdd): 2 V ~ 3.6 V
• Data Converters: A/D 12x12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Data Bus Width: 8 bit
• Data Ram Size: 4 KB
• Interface Type: SPI, USART, SPI, I2C
• Maximum Clock Frequency: 8 MHz
• Number Of Programmable I/os: 51
• Number Of Timers: 4
• Operating Supply Voltage: 2 V to 3.6 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 14
• Controller Family/series: PIC18F
• No. Of I/o's: 51
• Ram Memory Size: 3923Byte
• Cpu Speed: 48MHz
• No. Of Timers: 4
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

B.3.14
In order to suppress or attenuate the Idle tones present
in any Delta-Sigma ADCs, dithering can be applied to
the ADC. Dithering is the process of adding an error to
the ADC feedback loop in order to “decorrelate” the
outputs and “break” the Idle tones behavior. Usually a
random or pseudo-random generator adds an analog
or digital error to the feedback loop of the Delta-Sigma
ADC in order to ensure that no tonal behavior can
happen at its outputs. This error is filtered by the feed-
back loop and typically has a zero average value so
that the converter static transfer function is not dis-
turbed by the dithering process. However, the dithering
process slightly increases the noise floor (it adds noise
to the part) while reducing its tonal behavior, and thus,
improving SFDR and THD.
The dithering process scrambles the Idle tones into
baseband white noise and ensures that dynamic specs
(SNR, SINAD, THD, SFDR) are less signal dependent.
The AFE incorporates a proprietary dithering algorithm
on both ADCs in order to remove Idle tones and
improve THD, which is crucial for power metering
applications.
B.3.15
The crosstalk is defined as the perturbation caused by
one ADC channel on the other ADC channel. It is a
measurement of the isolation between the two ADCs
present in the chip.
This measurement is a two-step procedure:
1.
2.
The crosstalk is then the ratio between the output
power of the ADC when the perturbation is present and
when it is not divided by the power of the perturbation
signal.
A lower crosstalk value implies more independence
and isolation between the two channels.
The measurement of this signal is performed under the
following conditions:
• GAIN = 1
• PRESCALE = 1
• OSR = 256
• MCLK = 4 MHz
 2010 Microchip Technology Inc.
Measure one ADC input with no perturbation on
the other ADC (ADC inputs shorted).
Measure
perturbation sine wave signal on the other ADC
at a certain predefined frequency.
DITHERING
CROSSTALK
the
same
ADC
input
with
Preliminary
a
PIC18F87J72 FAMILY
Step 1
• CH0+ = CH0- = SAV
• CH1+ = CH1- = SAV
Step 2
• CH0+ = CH0- = SAV
• CH1+ – CH1- = 1V
The crosstalk is then calculated with the following
formula:
EQUATION B-10:
B.3.16
This is the ratio between a change in the power supply
voltage and the ADC output codes. It measures the
influence of the power supply voltage on the ADC
outputs.
The PSRR specification can be DC (the power supply
is taking multiple DC values) or AC (the power supply
is a sine wave at a certain frequency with a certain
common-mode). In AC, the amplitude of the sine wave
is representing the change in the power supply.
It is defined as:
EQUATION B-11:
Where V
output code translates to with the ADC transfer
function. For the AFE, SAV
5.5V, and for AC PSRR, a 50/60 Hz sine wave is
chosen, centered around 5V, with a maximum 500 mV
amplitude. The PSRR specification is measured with
SAV
sine wave)
DD
= SV
CTalk dB
OUT
PSRR
DD
PSRR dB
is the equivalent input voltage that the

.


=
P
-

10
SS
SS
SS
P
=
@ 50/60 Hz (full-scale
log
20


DD

-------------------------------- -

log
CH0Power
CH1Power


ranges from 4.5V to
--------------------- -


SAV
DS39979A-page 441
V
OUT
DD



