ATtiny3224/3226/3227

33.16 ADC

Operating conditions:

T_A = [-40, 125]°C
Sample rate defined for SAMPDUR = 0x02 with ADC in Free-Running mode
Applies for all allowed combinations of VREF selections and sample rates, unless otherwise specified
Characteristics are identical with and without PGA enabled, unless otherwise specified

Table 33-24. Power Supply, Reference and Input Range
Symbol	Description	Conditions	Min.	Typ.	Max.	Unit
V_DD	Supply Voltage		1.8	-	5.5	V
V_REF	Reference voltage	REFSEL = Internal Reference	1.024	-	V_DD - 0.5
		REFSEL = External Reference	1	-	5.5
		REFSEL = V_DD	1.8	-	5.5
C_IN	Input capacitance	PGA disabled	-	8	-	pF
C_IN	Input capacitance	PGA enabled	-	7	-	pF
R_IN	Input resistance		-	10	-	kΩ
V_IN	Input voltage range	Single-ended mode	0	-	V_REF	V
V_IN	Input voltage range	Differential mode	-0.1	-	V_DD + 0.1	V

Table 33-25. Clock and Timing Characteristics
Symbol	Description	Conditions		Min.	Typ.	Max.	Unit
f_{CLK_ADC}	Conversion rate	PGA disabled	REFSEL = Internal Reference	-	-	187	ksps
			REFSEL = External Reference	-	-	375
			REFSEL = V_DD	-	-	375
		PGA enabled	REFSEL = Internal Reference	-	-	107
			REFSEL = External Reference	-	-	181
			REFSEL = V_DD	-	-	181
CLK_ADC	ADC clock frequency	REFSEL = Internal Reference		300	-	3000	kHz
		REFSEL = External Reference		300	-	6000
		REFSEL = V_DD		300	-	6000
T_S	Sampling time	PGA disabled		0.5	-	255.5	CLK_ADC cycles
T_S	Sampling time	PGA enabled		1	-	256	CLK_ADC cycles

Table 33-26. Accuracy Characteristics External Reference⁽¹⁾
Symbol	Description	Conditions	Min.	Typ.	Max.	Unit
Res	Resolution		-	-	12	bit
E_INL	Integral nonlinearity	V_DD = 3.0V V_REF = 2.048V CLK_ADC = 2.5 MHz Differential mode	-2.0	0.8	2.0	LSb
E_DNL	Differential nonlinearity		-0.9	0.8	1.4
E_OFF	Offset error		-28	1.5	28
E_GAIN	Gain error		-2.1	0.6	2.1
E_T	Total unadjusted error		-	5	21

Note:

These values are based on characterization and are not covered by production test limits.

Table 33-27. Accuracy Characteristics Internal Reference⁽¹⁾
Symbol	Description	Conditions	Min.	Typ.	Max.	Unit
Res	Resolution		-	-	12	bit
E_INL	Integral nonlinearity	V_DD = 3.0V V_REF = 2.048V CLK_ADC = 2.5 MHz Differential mode	-2.3	1	2.3	LSb
E_DNL	Differential nonlinearity		-0.9	1	1.6
E_OFF	Offset error		-28	1.5	28
E_GAIN	Gain error		-81	7	81
E_T	Total unadjusted error		-	10	42

Note:

These values are based on characterization and are not covered by production test limits.

Table 33-28. Accuracy Characteristics with PGA Enabled⁽¹⁾
Symbol	Description	Conditions	Min.	Typ.	Max.	Unit
N_RMS	Input Noise	PGA Gain = 1V/V	-	32	-	µV_RMS
		PGA Gain = 2V/V	-	63	-
		PGA Gain = 4V/V	-	125	-
		PGA Gain = 8V/V	-	250	-
		PGA Gain = 16V/V	-	500	-
E_GAIN	Gain error V_DD = 3.0V	PGA Gain = 1V/V	-0.4	-0.2	0.4	%
		PGA Gain = 2V/V	-0.5	-0.2	0.5
		PGA Gain = 4V/V	-0.7	-0.3	0.7
		PGA Gain = 8V/V	-1.2	-0.6	1.2
		PGA Gain = 16V/V	-1.7	-0.8	1.7

Note:

These values are based on characterization and are not covered by production test limits.

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