Datasheet

Note:
1.
Current consumption is measured with AFEC_ACR.IBCTL=10.
2. In Sleep mode, the AFE core, the Sample and Hold and the internal reference operational amplifier are off.
3. In Fast Wake-up mode, only the AFE core is off.
59.8.1.2 ADC Bias Current
AFEC_ACR.IBCTL controls the ADC bias current with the nominal setting IBCTL = 10.
IBCTL = 10 is the mandatory configuration suitable for a sampling frequency of up to 1 MHz. If the sampling
frequency is below 500 kHz, IBCTL = 01 can be used to reduce the current consumption.
If the sampling frequency is more than 1 MHz, then the setting must be IBCTL=11.
Note: The default value in the register is 01, and it must be modified according to the defined sampling frequency.
59.8.2 External Reference Voltage
V
VREFP
is an external reference voltage applied on the pin VREFP. The quality of the reference voltage V
VREFP
is
critical to the performance of the AFE. A DC variation of the reference voltage V
VREFP
is converted to a gain error by
the AFE. The noise generated by V
VREFP
is converted by the AFE to count noise.
Table 59-30. VREFP Electrical Characteristics
Symbol Parameter Conditions Min. Typ. Max. Unit
V
VREFP
Voltage Range Full operational 1.7 – VDDIN V
RMS Noise (see Note 2) Bandwidth up to 1.74MHz
VREFP=1.7V
– – 120 µV
R
VREFP
Input DC Impedance AFE reference resistance bridge (see
Note 1)
– 4.7 – kOhm
Vin Input Linear Range (see Note 3) Operational Range 2 - 98 %VVREFP
I
VREFP
Current V
VREFP
= 3.3V – 0.8 – mA
Note:
1.
When the AFE is in Sleep mode, the VREFP impedance has a minimum of 10 MOhm.
2. Requested noise on VREFP.
3. Electrical parameters specified inside the operational range. Exceeding this range can introduce additional INL
error up to +/- 5 LSB and temperature dependency up to +/-10 LSB.
59.8.3 AFE Timings
Table 59-31. AFE Timing Characteristics
Symbol Parameter Conditions Min. Typ. Max. Unit
f
AFE Clock
Clock Frequency – 4 20 40 MHz
t
AFE Clock
Clock Period – 25 50 250 ns
f
S
Sampling Frequency (see Note 1) – – – 1.74 MHz
t
ST
ART
AFE Startup Time
Sleep mode to Normal mode – – 4 µs
Fast Wake-up mode to Normal mode - - 2 µs
Note: 1.f
s
= 1 / t
AFE_conv
in Free Run mode; otherwise defined by the trigger timing.
59.8.4 AFE Transfer Function
The first operation of the AFE is a sampling function relative to V
DAC
. V
DAC
is generated by an internal DAC0 or
DAC1. All operations after the Sample-and-Hold are dif
ferential relative to an internal common mode voltage V
CM
=
V
VREFP
/2.
SAM E70/S70/V70/V71 Family
Electrical Characteristics for SAM E70/S70
© 2019 Microchip T
echnology Inc.
Datasheet
DS60001527D-page 1880