RHF1401_12 STMICROELECTRONICS [STMicroelectronics], RHF1401_12 Datasheet - Page 25

• Manufacturer Part Number: RHF1401_12
• Description: Rad-hard 14-bit 30 Msps A/D converter
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

RHF1401
3
3.1
User manual
Optimizing the power consumption
The polarization current in the input stage is set by an external resistor (R
selecting the resistor value, it is possible to optimize the power consumption according to
the sampling frequency of the application. For this purpose, an external R
placed between the IPOL pin and the analog ground.
The values in
the input signal is 2 Vpp with a differential DC connection. If the conditions are changed, the
Rpol resistor varies slightly.
Figure 50
shows the minimum and maximum values to get good results. ENOB decreases by
approximately 0.2 dB when you change Rpol from optimum to maximum or minimum.
If Rpol is higher than the maximum value, there is not enough polarization current in the
analog stage to obtain good results. If Rpol is below the minimum, THD increases
significantly.
Therefore, the total dissipation can be adjusted across the entire sampling range to fulfill the
requirements of applications where power saving is critical.
For sampling frequencies below 2 MHz, the optimum resistor value is approximately
400 kOhms.
Figure 50. Rpol values vs. F
The power consumption depends on the Rpol value and the sampling frequency. In
Figure
defined in
51, it is shown with the internal references disabled (REFMODE = 1) and Rpol
shows the optimum Rpol resistor value to obtain the best ENOB value. It also
Figure 50
1000
100
10
1
Figure 50
0
as the optimum.
5
are achieved with VREFP = 1 V, VREFM = 0 V, INCM = 0.5 V and
10
Doc ID 13317 Rev 8
s
S ampling frequenc y (Ms ps )
15
20
25
30
maximum
optimum
minimum
35
pol
pol
). When
resistor is
40
User manual
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