Rainbow Electronics AT90LS4433 - Manual (Page 64)

64
AT90S/LS4433
1042G–AVR–09/02
Analog-to-Digital
Converter
Features • 10-bit Resolution
• ±2 LSB Absolute Accuracy
• 0.5 LSB Integral Non-linearity
• 65 - 260 µs Conversion Time
• Up to 15 kSPS
• Six Multiplexed Input Channels
• Rail-to-Rail Input Range
• Free Run or Single Conversion Mode
• Interrupt on ADC Conversion Complete
• Sleep Mode Noise Canceler
The AT90S4433 features a 10-bit successive approximation ADC. The ADC is con-
nected to a 6-channel Analog Multiplexer, which allows each pin of Port C to be used as
an input for the ADC. The ADC contains a Sample and Hold Amplifier, which ensures
that the input voltage to the ADC is held at a constant level during conversion. A block
diagram of the ADC is shown in Figure 44.
The ADC has two separate analog supply voltage pins: AVCC and AGND. AGND must
be connected to GND, and the voltage on AVCC must not differ from V
CC
more than
±0.3V. See the section “ADC Noise Canceling Techniques” on page 70 for how to con-
nect these pins.
An external reference voltage must be applied to the AREF pin. This voltage must be in
the range 2.0 - AVCC.
Figure 44. Analog-to-Digital Converter Block Schematic
ADC CONVERSION
COMPLETE IRQ
8-BIT DATA BUS
9 0
ADC MULTIPLEXER
SELECT (ADMUX)
ADC CTRL & STATUS
REGISTER (ADCSR)
ADC DATA REGISTER
(ADCH/ADCL)
MUX2 ADIE
ADIE
ADFR ADSC ADEN
ADIF
ADIF
MUX1 MUX0 ADPS0 ADPS1 ADPS2
6-
CHANNEL
MUX
CONVERSION LOGIC 10-BIT DAC
+
-
SAMPLE & HOLD
COMPARATOR
Analog
Inputs
External
Reference
Voltage