Datasheet

Data Sheet AD5421
Rev. G | Page 17 of 36
1.0
–1.0
–0.8
–0.6
–0.4
–0.2
0
0.2
0.6
0.8
0.4
0
1.0
0.90.80.70.60.50.40.30.20.1
VOLTAGE ACROSS 500Ω LOAD RESISTOR (mV)
TIME (Seconds)
V
LOOP
= 24V
EXT NMOS
INT V
REF
I
LOOP
= 4mA
R
LOAD
= 500Ω
T
A
= 25°C
1.33mV p-p
0.2mV rms
09128-023
Figure 25. Loop Current Noise, 500 Hz to 10 kHz Bandwidth
(HART Bandwidth)
6
5
4
3
2
1
0
–40 –30 –20 –10 0 10
20 30 40
VOLTAGE ACROSS 250Ω LOAD RESISTOR (V)
TIME (µs)
FALLING
RISING
V
LOOP
= 24V
EXT NMOS
R
LOAD
= 250Ω
T
A
= 25°C
C
IN
= OPEN CIRCUIT
09128-025
Figure 26. Full-Scale Loop Current Step
6
5
4
3
2
1
0
–1.0 –0.5 0
0.5 1.0 1.5 2.0 2.5 3.0
VOLTAGE ACROSS 250Ω LOAD RESISTOR (V)
TIME (ms)
FALLING
RISING
V
LOOP
= 24V
EXT NMOS
R
LOAD
= 250Ω
T
A
= 25°C
C
IN
= 22nF
09128-026
Figure 27. Full-Scale Loop Current Step, C
IN
= 22 nF
0.244
0.226
0.228
0.230
0.232
0.234
0.236
0.238
0.240
0.242
0
0.5
1.0
1.5 2.0
IODV
DD
CURRENT (µA)
DIGITAL LOGIC VOLTAGE (V)
DECREASING
INCREASING
IODV
DD
= 1.8V
T
A
= 25°C
09128-027
Figure 28. IODV
DD
Current vs. Digital Logic Voltage, Increasing and
Decreasing, IODV
DD
= 1.8 V
0.60
0.55
0.50
0.45
0.40
0 3.53.02.52.01.51.00.5
IODV
DD
CURRENT (µA)
DIGITAL LOGIC VOLTAGE (V)
IODV
DD
= 3.3V
T
A
= 25°C
DECREASING
INCREASING
09128-028
Figure 29. IODV
DD
Current vs. Digital Logic Voltage, Increasing and
Decreasing, IODV
DD
= 3.3 V
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0 6
54321
IODV
DD
CURRENT (µA)
DIGITAL LOGIC VOLTAGE (V)
IODV
DD
= 5V
T
A
= 25°C
DECREASING
INCREASING
09128-029
Figure 30. IODV
DD
Current vs. Digital Logic Voltage, Increasing and
Decreasing, IODV
DD
= 5 V