AD5421_11 AD [Analog Devices], AD5421_11 Datasheet - Page 27

• Manufacturer Part Number: AD5421_11
• Description: 16-Bit, Serial Input, Loop-Powered, 4 mA to 20 mA DAC
• Manufacturer: AD [Analog Devices]

FAULT REGISTER
The read-only fault register is addressed as described in Table 11. The bits in the fault register indicate a range of possible fault conditions.
Table 18. Fault Register Bit Map
MSB
D15
SPI
Table 19. Fault Register Bit Descriptions
Fault Alert
SPI
PEC (packet
error check)
I
I
Temp 140°C
Temp 100°C
V
V
V
ature value
On-Chip ADC Transfer Function Equations
The transfer function equation for the measurement of the
voltage between the V
where D is the 8-bit digital code returned by the on-chip ADC.
LOOP
LOOP
LOOP
LOOP
LOOP
Over
Under
/temper-
V
6V
12V
LOOP
D14
PEC
− COM = (2.5/256) × D
FAULT
Pin Set
Yes
Yes
Yes
Yes
Yes
No
Yes
No
N/A
D13
I
Over
LOOP
LOOP
and COM pins is as follows:
D12
I
Under
Description
This bit is set high to indicate the loss of the SPI interface signaling. This fault occurs if there is no valid
communication to the AD5421 over the SPI interface for more than the user-defined timeout period. The
occurrence of this fault also forces the loop current to the alarm value if Bit D10 of the control register is at
Logic 0. The alarm current direction is determined by the state of the ALARM_CURRENT_DIRECTION pin.
This bit is set high when an error in the SPI communication is detected using cyclic redundancy check (CRC)
error detection. See the Packet Error Checking section for more information.
This bit is set high when the actual loop current is greater than the programmed loop current.
This bit is set high when the actual loop current is less than the programmed loop current.
This bit is set high to indicate an overtemperature fault. This bit is set if the die temperature of the AD5421
exceeds approximately 140°C. This bit is cleared when the temperature returns below approximately 125°C.
This bit is set high to indicate an increasing temperature of the AD5421. This bit is set if the die temperature of the
AD5421 exceeds approximately 100°C. This bit is cleared when the temperature returns below approximately 85°C.
This bit is set high when the voltage between the V
a 6 V loop supply voltage with 20:1 resistor divider connected at V
above approximately 0.4 V.
This bit is set high when the voltage between the V
a 12 V loop supply voltage with 20:1 resistor divider connected at V
above approximately 0.7 V.
These eight bits represent either the voltage between the V
depending on the setting of Bit D8 of the control register (see the On-Chip ADC Transfer Function Equations section).
8-Bit Value
00000000
…
11111111
LOOP
D11
Temp
140°C
D10
Temp
100°C
V
0
…
2.49
D9
V
6V
LOOP
LOOP
Rev. 0 | Page 27 of 32
− COM Voltage (V)
D8
V
12V
LOOP
The transfer function equation for the die temperature is
as follows:
where D is the 8-bit digital code returned by the on-chip ADC.
D7
LOOP
LOOP
Die Temperature = 125 − (1.771 × (D − 128))
and COM pins falls below approximately 0.3 V (representing
and COM pins falls below approximately 0.6 V (representing
D6
LOOP
Die Temperature (°C)
+300
…
−55
and COM pins or the AD5421 die temperature,
LOOP
D5
LOOP
). This bit is cleared when the voltage returns
). This bit is cleared when the voltage returns
V
LOOP
D4
/temperature value
D3
D2
D1
AD5421
LSB
D0