AT90LS2333-4AI Atmel, AT90LS2333-4AI Datasheet - Page 57

• Manufacturer Part Number: AT90LS2333-4AI
• Description: IC MCU 2K 4MHZ A/D LV IT 32TQFP
• Manufacturer: Atmel
• Series: AVR® 90LSr

Specifications of AT90LS2333-4AI

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 4MHz
• Connectivity: SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 20
• Program Memory Size: 2KB (1K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 128 x 8
• Ram Size: 128 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 6 V
• Data Converters: A/D 6x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 32-TQFP, 32-VQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

ADC Data Register - ADCL AND ADCH
When an ADC conversion is complete, the result is found in these two registers. In free-run mode, it is essential that both
registers are read, and that ADCL is read before ADCH.
Scanning Multiple Channels
Since change of analog channel always is delayed until a conversion is finished, the Free Run Mode can be used to scan
multiple channels without interrupting the converter. Typically, the ADC Conversion Complete interrupt will be used to per-
form the channel shift. However, the user should take the following fact into consideration:
The interrupt triggers once the result is ready to be read. In Free Run Mode, the next conversion will start immediately
when the interrupt triggers. If ADMUX is changed after the interrupt triggers, the next conversion has already started, and
the old setting is used.
ADC Noise Canceling Techniques
Digital circuitry inside and outside the AT90S2333/4433 generates EMI which might affect the accuracy of analog measure-
ments. If conversion accuracy is critical, the noise level can be reduced by applying the following techniques:
1. The analog part of the AT90S2333/4433 and all analog components in the application should have a separate analog
ground plane on the PCB. This ground plane is connected to the digital ground plane via a single point on the PCB.
2. Keep analog signal paths as short as possible. Make sure analog tracks run over the analog ground plane, and keep
them well away from high-speed switching digital tracks.
3. The AV
shown in Figure 47.
4. Use the ADC noise canceler function to reduce induced noise from the CPU.
5. If some Port C pins are used as digital outputs, it is essential that these do not switch while a conversion is in progress.
Bit
$05 ($25)
$04 ($26)
Read/Write
Initial value
CC
pin on the AT90S2333/4433 should be connected to the digital V
ADC7
15
R
R
7
0
0
-
ADC6
14
R
R
6
0
0
-
ADC5
13
R
R
5
0
0
-
ADC4
12
R
R
4
0
0
-
AT90S/LS2333 and AT90S/LS4433
ADC3
11
R
R
3
0
0
-
ADC2
10
R
R
2
0
0
-
ADC9
ADC1
R
R
9
1
0
0
CC
supply voltage via an RC network as
ADC8
ADC0
R
R
8
0
0
0
ADCH
ADCL
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