RHF1401_12 Datasheet, PDF (31/42 Pages) STMicroelectronics – Rad-hard 14-bit 30 Msps A/D converter

RHF1401
User manual
3.3
3.3.1
Reference connections
Internal voltage reference
In standard configuration, the ADC is biased with two internal voltage references: VREFP
and INCM. They should be decoupled to minimize low and high frequency noise. When the
REFMODE pin is set to 0 both internal voltage references are enabled and they can drive
external components or be forced by an external value.
The VREFM pin has no internal reference and must be connected to a voltage reference. It
is usually connected to the analog ground.
Figure 58. Internal voltage reference setting
As close as possible
to the ADC pins
100 nF*
470 nF*
VREFP
VIN
VINB
INCM
REFMODE VREFM
100 nF*
470 nF*
*the use of a ceramic technology is
preferable for a large bandwidth
stability of the capacitor.
AM04574
3.3.2
External voltage reference
External voltage references can be used for specific applications requiring better linearity,
enhanced temperature behavior, or different voltage values (see Table 7: Internal reference
voltage). Internal voltage references are disabled when the REFMODE pin is equal to 1. In
this case, external voltage references must be applied to the device.
External voltage references can be applied when internal voltage references are disabled or
not.
When internal voltage reference are disabled, ADC consumption is about 13 mA less than
when they are enabled.
The external voltage references with the configuration shown in Figure 59 and Figure 60
can be used to obtain optimum performance. Decoupling is achieved by using ceramic
capacitors, which provide optimum linearity versus frequency.
Doc ID 13317 Rev 8
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