Rainbow Electronics MAX1329 - Manual (Page 27)

MAX1329/MAX1330
12-/16-Bit DASs with ADC, DACs, DPIOs, APIOs,
Reference, Voltage Monitors, and Temp Sensor
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For external clock mode, disable the internal oscillator,
which then configures CLKIO as an input. Apply an
external clock at CLKIO with a frequency up to 20MHz.
The input clock divider can be set to 1, 2, or 4. The out-
put of the CLKIO input divider goes to the input of
charge pump and ADC clock dividers.
Note: When using the internally generated clock, enter-
ing shutdown or sleep mode causes CLKIO to become
an input. To prevent crowbar current, connect a 500kΩ
resistor from CLKIO to DGND.
Digital and Analog Programmable I/Os
The MAX1329/MAX1330 provide four digital programma-
ble I/Os (DPIO1–DPIO4) and four analog programmable
I/Os (APIO1–APIO4). The DPIOs and APIOs can be con-
figured as logic inputs or outputs through the DPIO and
APIO Control registers. The DPIOs are powered by
DV
DD . Likewise, the APIOs are powered by AV DD . When
configured as inputs, internal pullups can be enabled
through the DPIO and APIO Setup registers.
Digital Programmable I/O
DPIO1–DPIO4 are powered by DV DD and are program-
mable as the following:
• General-purpose input
• Wake-up input (internal oscillator enable)
• Power-down mode (sleep or shutdown) control input
• DAC loading or sequencing input
• ADC acquisition and conversion control input
• DAC, op amp, and SPDT switch control input
• ADC data-ready output
• General-purpose output
Analog Programmable I/O
APIO1–APIO4 are powered by AV DD and are program-
mable as the following:
• General-purpose input
• Wake-up input (internal oscillator enable)
• General-purpose output
• Digital input/output for signals to be level-shifted
from/to the SPI interface
Temperature Sensor
An internal temperature sensor measures the device
temperature of the MAX1329/MAX1330. The ADC con-
verts the analog measurement from the internal temper-
ature sensor to a digital output (see Table 1). The
temperature measurement resolution is +0.125°C for
each LSB and the measured temperature can be calcu-
lated using the following equation:
T = ADC output data/8°C
where ADC output data is the decimal value of the
two’s complement result.
The MAX1329/MAX1330 support external single-ended
and differential temperature measurements using a diode
connected transistor between AIN1 and AGND, AIN2 and
AGND, or AIN1 and AIN2. Select the appropriate channel
for conversion through the ADC Setup register.
Voltage References
The internal unbuffered 2.5V reference is externally
accessible at REFADJ. Separate ADC and DAC refer-
ence buffers are programmable to output 1.25V, 2.048V,
or 2.5V REFADC and REFDAC. The reference and
buffers can be individually controlled through the ADC
Control and DAC Control registers. Power down the
internal reference to apply an external reference at
REFADJ as an input to the ADC and DAC reference
buffers. Power down the reference buffers to apply exter-
nal references directly at REFADC and REFDAC.
Note: All temperature sensor measurements use the
voltage at REFADJ as a reference and require a 2.5V ref-
erence for accurate results.
Operational Amplifiers
The MAX1329 includes one uncommitted operational
amplifier. The MAX1330 includes two op amps. These
op amps feature rail-to-rail inputs and outputs, with a
bandwidth of 1MHz. The op amps are powered down
through the DAC Control register. An internal analog
switch shorts the negative input to the output when
enabled through the Switch Control register or a DPIO
configured as a switch control input. When powered
down, the outputs of the op amps go high impedance.
ADC OUTPUT DATA TEMPERATURE
(°C) TWO’S COMPLEMENT HEX
+85.000 0010 1010 1000 2A8
+70.000 0010 0011 0000 230
+25.000 0000 1100 1000 0C8
+0.250 0000 0000 0010 002
+0.125 0000 0000 0001 001
0 0000 0000 0000 000
-0.125 1111 1111 1111 FFF
-0.250 1111 1111 1110 FFE
-25.000 1111 0011 1000 F38
-40.000 1110 1100 0000 EC0
Table 1. Temperature vs. ADC Output