MAX1231EVKIT Maxim Integrated Products, MAX1231EVKIT Datasheet - Page 11

• Manufacturer Part Number: MAX1231EVKIT
• Description: EVAL KIT FOR MAX1231
• Manufacturer: Maxim Integrated Products

Specifications of MAX1231EVKIT

• Number Of Adc's: 1
• Number Of Bits: 12
• Sampling Rate (per Second): 300k
• Data Interface: Serial
• Inputs Per Adc: 16 Single Ended or 8 Differential
• Input Range: ±VREF/2
• Power (typ) @ Conditions: 1.86mW @ 300kSPS
• Voltage Supply Source: Single Supply
• Operating Temperature: 0°C ~ 70°C
• Utilized Ic / Part: MAX1231
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Address the unipolar and bipolar registers through the
setup register (bits 1 and 0). Program a pair of analog
channels for differential operation by writing a 1 to the
appropriate bit of the bipolar or unipolar register.
Unipolar mode sets the differential input range from 0
to V
mode causes the digital output code to be zero.
Selecting bipolar mode sets the differential input range
to ±V
mode and two’s complement in bipolar mode (Figures
8 and 9).
In single-ended mode, the MAX1227/MAX1229/
MAX1231 always operate in unipolar mode. The analog
inputs are internally referenced to GND with a full-scale
input range from 0 to V
The equivalent circuit of Figure 3 shows the MAX1227/
MAX1229/MAX1231s’ input architecture. In track mode,
a positive input capacitor is connected to AIN0–AIN15
in single-ended mode (and AIN0, AIN2, AIN4…AIN14
in differential mode). A negative input capacitor is con-
nected to GND in single-ended mode (or AIN1, AIN3,
AIN5…AIN15 in differential mode). For external T/H
timing, use clock mode 01. After the T/H enters hold
mode, the difference between the sampled positive
and negative input voltages is converted. The time
required for the T/H to acquire an input signal is deter-
mined by how quickly its input capacitance is charged.
If the input signal’s source impedance is high, the
required acquisition time lengthens. The acquisition
Figure 3. Equivalent Input Circuit
REF
(SINGLE ENDED);
(SINGLE ENDED);
(DIFFERENTIAL)
(DIFFERENTIAL)
AIN4…AIN14
AIN5…AIN15
REF
AIN0-AIN15
AIN0, AIN2,
AIN1, AIN3,
. A negative differential analog input in unipolar
GND
/2. The digital output code is binary in unipolar
True Differential Analog Input T/H
HOLD
______________________________________________________________________________________
REF
GND
REF
V
.
HOLD
CIN+
CIN-
DD
/2
DAC
Unipolar/Bipolar
Temp Sensor, Internal Reference
12-Bit 300ksps ADCs with FIFO,
COMPARATOR
HOLD
+
-
time, t
be acquired, plus the power-up time. It is calculated by
the following equation:
where R
input signal, and t
device. The varying power-up times are detailed in the
explanation of the clock mode conversions.
t
ance below 300Ω does not significantly affect the
ADC’s AC performance. A high-impedance source can
be accommodated either by lengthening t
placing a 1µF capacitor between the positive and neg-
ative analog inputs.
The MAX1227/MAX1229/MAX1231 contain a FIFO
buffer that can hold up to 16 ADC results plus one tem-
perature result. This allows the ADC to handle multiple
internally clocked conversions and a temperature mea-
surement, without tying up the serial bus.
If the FIFO is filled and further conversions are request-
ed without reading from the FIFO, the oldest ADC
results are overwritten by the new ADC results. Each
result contains 2 bytes, with the MSB preceded by four
leading zeros. After each falling edge of CS, the oldest
available byte of data is available at DOUT, MSB first.
When the FIFO is empty, DOUT is zero.
The first 2 bytes of data read out after a temperature
measurement always contain the temperature result
preceded by four leading zeros, MSB first. If another
temperature measurement is performed before the first
temperature result is read out, the old measurement is
overwritten by the new result. Temperature results are
in degrees Celsius (two’s complement) at a resolution
of 1/8 of a degree. See the Temperature Measurements
section for details on converting the digital code to a
temperature.
The MAX1227/MAX1229/MAX1231 operate from an
internal oscillator, which is accurate within 10% of the
4.4MHz nominal clock rate. The internal oscillator is
active in clock modes 00, 01, and 10. Read out the
data at clock speeds up to 10MHz. See Figures
4–7 for details on timing specifications and starting a
conversion.
ACQ
THD
is never less than 1.4µs, and any source imped-
ACQ
IN
=
, is the maximum time needed for a signal to
= 1.5kΩ, R
20 x log
PWR
⎛
⎜
⎝
S
(
= 1µs, the power-up time of the
V
is the source impedance of the
2
2
+
V
3
2
+
V
Internal Clock
4
Internal FIFO
2
+
V
5
ACQ
2
)
/ V
or by
1
⎞
⎟
⎠
11