Maxim-integrated MAXQ7666 Uživatelský manuál Strana 95

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SECTION 3: ANALOG I/O MODULE
The MAXQ7665/MAXQ7666 contain an ultra-low-power precision analog I/O module for measuring and controlling a host of sensors,
motors, bridges, and other analog peripherals. The analog I/O module has all the components to make the MAXQ7665/MAXQ7666
stand-alone data-acquisition machines ideal for harsh environment applications. Except where explicitly noted, the MAXQ7665 and
MAXQ7666 support identical features.
The analog I/O module includes the following features:
8 differential analog-input multiplexer
Low-power, 12-bit, 500ksps successive approximation ADC
12-bit, buffered, voltage-output DAC
On-chip ±1°C accurate temperature sensor (typ)
Remote temperature sensor drive circuit
Internal programmable gain amplifier (x1, x2, x4, x8, x16, x32)
Individual external reference inputs for the ADC and DAC
3.1 Architecture
The analog-input multiplexer supports 8 differential measurements and feeds the programmable gain amplifier (PGA) and the 12-bit
SAR ADC. The low noise, programmable gain amplifier with gains of x1 to x32 allows interfacing to a variety of devices with different
signal amplitudes. The ADC conversion clock source is the same as the system clock source (internal oscillator or external
crystal/clock) and has a user-programmable clock division ratio. The 12-bit voltage-out DAC has internal feedback resistors for reduc-
ing external component count. The internal temperature sensor performs temperature measurements with an internal diode-connect-
ed transistor. In the remote temperature sensor drive configuration, the device provides the proper bias necessary to measure tem-
perature with up to two external diode-connected transistor sensors. The MAXQ7665/MAXQ7666 support independent external refer-
ence inputs for the ADC and DAC to allow the use of high precision, high quality reference sources.
Figure 3-1 shows a functional block diagram of the MAXQ7665/MAXQ7666 analog I/O module.
MAXQ7665/MAXQ7666 Users Guide
3-5
Figure 3-1. Analog I/O Module Block Diagram
AIN0
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
AIN7
AIN8
AIN9
AIN10
AIN11
AIN12
AIN13
AIN14
AIN15
PGAE
DACE
12-BIT
500kHz
ADC
12-BIT
DAC
PGA
DATA BUS (15:0)
ANALOG I/O FUNCTIONAL BLOCKS
8 DIFFERENTIAL
CHANNEL
MULTIPLEXER
TIMER 2
TIMER 1
TIMER 0
ADCCLK
VDAC
INTERNAL
TEMP
SENSOR
REFADC
REFDAC
50kΩ
50kΩ
TSE
PGG[2:0]
ADCDIFADCMX[4:0]
P0.5/
DACLOAD
P0.4/
ADCCNV
ADCSADCE
ADCBY ADCDUL
ADCBIP
ADCASD
Maxim Integrated
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