Datasheet

AD5410/AD5420 Data Sheet
Rev. F | Page 24 of 32
The time it takes for the output current to slew over a given
output range can be expressed as follows:
SizeLSBFrequencyClockUpdateSizeStep
ChangeOutput
TimeSlew
××
=
(1)
where:
Slew Time is expressed in seconds.
Output Change is expressed in amps.
When the slew rate control feature is enabled, all output
changes change at the programmed slew rate. If the CLEAR
pin is asserted, the output slews to the zero-scale value at the
programmed slew rate. The output can be halted at its current
value with a write to the control register. To avoid halting the
output slew, the slew active bit can be read to check that the
slew has completed before writing to any of the AD5410/
AD5420 registers (see Table 17). The update clock frequency for
any given value is the same for all output ranges. The step size,
however, varies across output ranges for a given value of step
size because the LSB size is different for each output range.
Table 20 shows the range of programmable slew times for a full-
scale change on any of the output ranges. The values in Table 20
were obtained using Equation 1. The digital slew rate control
feature results in a staircase formation on the current output, as
shown in Figure 47. Figure 47 also shows how the staircase can
be removed by connecting capacitors to the CAP1 and CAP2
pins, as described in the I
OUT
Filtering Capacitors section.
Table 20. Programmable Slew Time Values in Seconds for a Full-Scale Change on Any Output Range
Step Size (LSBs)
Update Clock Frequency (Hz) 1 2 4 8 16 32 64 128
257,730 0.25 0.13 0.06 0.03 0.016 0.008 0.004 0.0020
198,410 0.33 0.17 0.08 0.04 0.021 0.010 0.005 0.0026
152,440 0.43 0.21 0.11 0.05 0.027 0.013 0.007 0.0034
131,580 0.50 0.25 0.12 0.06 0.031 0.016 0.008 0.0039
115,740
0.57
0.28
0.14
0.07
0.035
0.018
0.009
0.0044
69,440 0.9 0.47 0.24 0.12 0.06 0.03 0.015 0.007
37,590 1.7 0.87 0.44 0.22 0.11 0.05 0.03 0.014
25,770 2.5 1.3 0.64 0.32 0.16 0.08 0.04 0.020
20,160 3.3 1.6 0.81 0.41 0.20 0.10 0.05 0.025
16,030 4.1 2.0 1.0 0.51 0.26 0.13 0.06 0.03
10,290 6.4 3.2 1.6 0.80 0.40 0.20 0.10 0.05
8280 7.9 4.0 2.0 1.0 0.49 0.25 0.12 0.06
6900 9.5 4.8 2.4 1.2 0.59 0.30 0.15 0.07
5530 12 5.9 3.0 1.5 0.74 0.37 0.19 0.09
4240 15 7.7 3.9 1.9 0.97 0.48 0.24 0.12
3300
20
9.9
5.0
2.5
1.24
0.62
0.31
0.16