MC68HC16Z1CPV25 Freescale Semiconductor, MC68HC16Z1CPV25 Datasheet - Page 203

• Manufacturer Part Number: MC68HC16Z1CPV25
• Description: IC MPU 1K RAM 25MHZ 144-LQFP
• Manufacturer: Freescale Semiconductor
• Series: HC16r

Specifications of MC68HC16Z1CPV25

• Core Processor: CPU16
• Core Size: 16-Bit
• Speed: 25MHz
• Connectivity: EBI/EMI, SCI, SPI
• Peripherals: POR, PWM, WDT
• Number Of I /o: 16
• Program Memory Type: ROMless
• Ram Size: 1K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 144-LQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -
• Program Memory Size: -
• Other names: Q1141110

M68HC16 Z SERIES
USER’S MANUAL
Grounding is the most important factor influencing analog circuit performance in mixed
signal systems (or in stand-alone analog systems). Close attention must be paid to
avoid introducing additional sources of noise into the analog circuitry. Common sourc-
es of noise include ground loops, inductive coupling, and combining digital and analog
grounds together inappropriately.
The problem of how and when to combine digital and analog grounds arises from the
large transients which the digital ground must handle. If the digital ground is not able
to handle the large transients, the current from the large transients can return to
ground through the analog ground. It is the excess current overflowing into the analog
ground which causes performance degradation by developing a differential voltage
between the true analog ground and the microcontroller’s ground pin. The end result
is that the ground observed by the analog circuit is no longer true ground and often
ends in skewed results.
Two similar approaches designed to improve or eliminate the problems associated
with grounding excess transient currents involve star-point ground systems. One ap-
proach is to star-point the different grounds at the power supply origin, thus keeping
the ground isolated. Refer to
Another approach is to star-point the different grounds near the analog ground pin on
the microcontroller by using small traces for connecting the non-analog grounds to the
analog ground. The small traces are meant only to accommodate DC differences, not
AC transients.
PCB
Figure 8-6 Star-Ground at the Point of Power Supply Origin
+5V
ANALOG POWER SUPPLY
Freescale Semiconductor, Inc.
AGND
ADC
For More Information On This Product,
ANALOG-TO-DIGITAL CONVERTER
Figure
Go to: www.freescale.com
+5V
VDD
VSS
8-6.
DIGITAL POWER SUPPLY
PGND
+5V
ADC POWER SCHEM
8-17