Independent A/D Converter Supply And Reference Voltage - ST STM32L152-EVAL Application Note

AN3216
2.1.1

Independent A/D converter supply and reference voltage

To improve conversion accuracy, the ADC and the DAC have an independent power supply
that can be filtered separately, and shielded from noise on the PCB.
●
The ADC voltage supply input is available on a separate V
●
An isolated supply ground connection is provided on the V
V and V
DDA
(see I (ADCx), I
DD
further information).
When available (depending on the package), V
On BGA 64-pin and all 100-pin packages
To ensure a better accuracy on low-voltage inputs and outputs, the user can connect to
V , a separate external reference voltage which is lower than V
REF+
voltage, represented by the full scale value, for an analog input (ADC) or output (DAC)
signal.
●
For ADC
–
–
–
–
–
●
For DAC
–
On packages with 64 pins or less (except BGA package)
V and V
REF+
supply (V
require a stable voltage. The consumption on V
REF
(DAC), I
DD DD
2.4 V ≤ V
= V
REF+ DDA
1.8 V ≤ V
= V
REF+ DDA
2.4 V ≤ V ≠ V
REF+ DDA
1.8 V ≤ V
< V
REF+ DDA
When product voltage range 3 is selected (V
(ADCCLK = 4 MHz, 250 Ksps)
1.8 V≤ V < V
REF+ DDA
pins are not available. They are internally connected to the ADC voltage
REF-
) and ground (V
DDA SSA
Doc ID 17496 Rev 5
(COMPx), I , and I
VDDA
must be tied to V
REF¨
for full speed (ADCCLK = 16 MHz, 1 Msps)
for medium speed (ADCCLK = 8 MHz, 500 Ksps)
for medium speed (ADCCLK = 8 MHz, 500 Ksps)
for low speed (ADCCLK = 4 MHz, 250 Ksps)
).
pin
DDA
pin
SSA
can reach several mA
DDA
in the product datasheets for
VREF
.
SSA
. V
DD REF+
= 1.2 V), the ADC is low speed
CORE
Power supplies
is the highest
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