Test And Diagnostic Tools; Vsci Signal Chain Input Test Pin; Vsco; Sco Analog Signal Chain Output Test Pin - Analog Devices ADXL180 iMEMS Manual

TEST AND DIAGNOSTIC TOOLS

V SIGNAL CHAIN INPUT TEST PIN
SCI
The V signal chain input test pin allows the excitation of the
SCI
signal chain from the input of the sensor interface circuitry
(sensor amplifier) through to the output of the current mode
serial port. The function of this pin becomes active after the pin
input voltage exceeds the level of about 0.8 V. Below this level,
the ADXL180 does not respond to the voltage applied to the
V pin. Above the threshold limit of 0.8 V, the voltage signal at
SCI
the V pin is applied to the sensor interface circuitry in parallel
SCI
with the sensor signal.
The applied signal is zero when the input signal is equal to the
common-mode potential of the sensor interface circuitry
(~V /2 V), see Figure 32. The V
DD
is typically about 640 μV/g. The scaling of the V
to the ADC code output is dependent on the range setting of
the part.
+600g
0g
–600g
~0.8
V
SCI
Figure 32. V Signal Chain Input Test Pin Transfer Function
SCI
input scaling for all ranges
SCI
input voltage
SCI
V /2 ~3.2
DD
TEST PIN VOLTAGE
V ANALOG SIGNAL CHAIN OUTPUT TEST PIN
SCO
The V analog signal chain output test pin provides access to
SCO
the sensor signal chain analog output voltage at the output of
the Bessel filter. This signal is filtered and ranged as defined by
the configuration register settings. It is before the digital auto-
zero function in the signal chain. Therefore, it is not auto-
zeroed. The configuration register SCOE bit must be set to 1 to
enable this output. The signal output resistance is typically
50 Ω. Connect this output to a high impedance input only.
Table 40. SCOE V
SCOE Definition
0 V output disabled. (Default.)
SCO
1 V output enabled. Analog output prior to ADC
SCO
conversion is present on V
impedance input, or data or sensor data may be
adversely affected.
Table 41. Typical V
g-Range
50 g
100 g
150 g
200 g
250 g
350 g
500 g
Rev. 0 | Page 43 of 56
Signal Chain Output Enable
SCO
pin. Connect V
SCO
Sensitivity Per g-Range
SCO
Sensitivity
32.8 mV/g
16.4 mV/g
10.8 mV/g
8.2 mV/g
6.56 mV/g
4.69 mV/g
3.28 mV/g
ADXL180
to high
SCO