MAX1460 Datasheet, PDF (16/20 Pages) Maxim Integrated Products – Low-Power, 16-Bit Smart ADC

Low-Power, 16-Bit Smart ADC
This algorithm minimizes the error directly at the six test
conditions, AS, AL, BS, BL, CS, and CL. Space the
temperatures A, B, and C widely to minimize the signal-
to-noise ratio of the measurement. If there is a large
error remaining in the finished product, move the cali-
bration temperatures closer to the peak error tempera-
tures. Similarly, full-scale sensor excitation may not be
the best calibration condition if the sensor has non-
linearities. Move S and L away from full scale.
Figure 6 shows the characteristics of an individual
Lucas-NovaSensor model NPH8-100-EH, 0 to 15psig,
silicon pressure sensor. Figure 7 shows the result of the
compensated sensor/MAX1460 pair.
Using the Compensated
Sensor/MAX1460 Pair
After calibration and removal from the test system, the
MAX1460 and the sensor form a mated pair. The START
pin can be connected to V_DD or left unconnected if the
sensor does not require a significant warm-up time. Now
operation is simple: just apply power and latch the paral-
lel output D when EOC falls. Temperature is digitized dur-
ing the first half of t_ADC, so the MAX1460 provides a
minimum sensor warm-up time of 35ms. Using a 2MHz
resonator, the conversion time t_CONV is nominally 67ms. If
the Repeat Mode bit is set, conversions repeat at a rate of
15Hz.
If the sensor requires more than 35ms of warm-up time,
the START pin may be used to initiate conversion (Figure
5). If the Repeat Mode bit is set, START should remain
high. If the Repeat Mode bit is reset, START may be used
to externally control the conversion rate of the MAX1460.
After the 12-bit parallel output D is latched, end the con-
version by taking START low for at least one clock cycle.
The output DAC converts the parallel digital output into
a serial bitstream on OUT. A simple external lowpass
filter, using the MAX1460 op amp, converts the OUT
bitstream into a ratiometric analog voltage (Figure 8).
The filter shown is an inverting configuration, but the
Gain and D_OFF coefficients of the characteristic equa-
tion can be adjusted to obtain either polarity. If the op
amp is not used, it can be powered down using the Op
Amp Power-Down bit in the configuration register.
The MAX1460 requires a minimum of external compo-
nents:
• One power-supply bypass capacitor (C1) from V_DD
to V_SS.
• One 2MHz ceramic resonator (X₁).
• Two 10kΩ resistors for the AGND pin.
• If an analog output is desired, two 500kΩ resistors
and a 1µF capacitor are needed for filtering.
MAX1460 Evaluation/
Development Kit
The MAX1460 evaluation kit (EV kit) speeds the devel-
opment of MAX1460-based transducer prototypes and
test systems. First-time users of the MAX1460 are
strongly encouraged to use this kit, which includes:
1) Evaluation board, with a MAX1460 sample and a sili-
con pressure sensor, ready for customer evaluation.
2) Interface board that must be connected to a PC par-
allel port.
3) MAX1460 communication/compensation software
(Windows compatible), which enables programming
of the MAX1460 one module at a time.
4) Detailed Design/Applications manual, developed for
sensor-test engineers.
The evaluation kit order number is MAX1460EVKIT.
Pin Configuration
N.C. 1
N.C. 2
AGND 3
START 4
I.C. 5
D6 6
D7 7
D8 8
D9 9
D10 10
D11 11
N.C. 12
MAX1460
36 N.C.
35 AMP-
34 AMP+
33 AMPOUT
32 N.C.
31 N.C.
30 OUT
29 D5
28 D4
27 D3
26 D2
25 D1
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