ATmega8A

26.9Bod Thresholds and Analog Comparator Offset

Figure 26-46. BOD Thresholds vs. Temperature (BOD Level is 4.0V)

Threshold (V)

3.95

Rising Vcc

3.9

3.85

3.8

Falling Vcc

3.75

3.7

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

90

Temperature (°C)

Figure 26-47. BOD Thresholds vs. Temperature (BOD Level is 2.7v)

Threshold (V)

2.8

2.75

Rising Vcc

2.7

2.65

Falling Vcc

2.6

2.55

2.5

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

90

Temperature (°C)

275

8159C–AVR–07/09

ATmega8A

Figure 26-48. Bandgap Voltage vs. VCC

Bandgap Voltage (V)

1.215
1.21	85	°C
	25	°C
1.205
1.2	-40	°C
1.195
1.19
1.185

1.18

2.5

3

3.5

4

4.5

5

5.5

Vcc (V)

Figure 26-49. Analog Comparator Offset Voltage vs. Common Mode Voltage (VCC = 5V)

Comparator Offset Voltage (V)

0.003

0.002

0.001

	85 °C
0	25 °C

-0.001

-0.002

-0.003

-40 °C

-0.004

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Common Mode Voltage (V)

276

8159C–AVR–07/09

ATmega8A

Figure 26-50. Analog Comparator Offset Voltage vs. Common Mode Voltage (VCC = 2.8V)

Comparator Offset Voltage (V)

0.003

0.002

25 °C

85 °C

0.001

0

-0.001

-40 °C

-0.002

-0.003

-0.004

0.25

0.50

0.75

1.00

1.25

1.5

1.75

2.00

2.25

2.50

2.75

Common Mode Voltage (V)

26.10 Internal Oscillator Speed

Figure 26-51. Watchdog Oscillator Frequency vs. VCC

FRC (kHz)

1050						25	°C
						85	°C
						-40	°C
1025
1000
975
950
925
2.5	3	3.5	4	4.5	5	5.5

VCC (V)

277

8159C–AVR–07/09

ATmega8A

Figure 26-52. Calibrated 8 MHz RC Oscillator Frequency vs. Temperature

FRC (MHz)

8,5

8

5.5 V

7,5

4.0 V

7

2.7 V

6,5

6

-40

-20

0

20

40

60

80

100

Temperature (°C)

Figure 26-53. Calibrated 8 MHz RC Oscillator Frequency vs. VCC

FRC (MHz)

8.5

-40 °C

25 °C

8

85 °C

7.5

7

6.5

6

2.5

3

3.5

4

4.5

5

5.5

VCC (V)

278

8159C–AVR–07/09

ATmega8A

Figure 26-54. Calibrated 8 MHz RC Oscillator Frequency vs. Osccal Value

	14
	12																25 °C
	10
(MHz)	8
RC
F
	6
	4
	2
	0	16	32	48	64	80	96	112	128	144	160	176	192	208	224	240	256

OSCCAL VALUE

Figure 26-55. Calibrated 4 MHz RC Oscillator Frequency vs. Temperature

FRC (MHz)

4.1

4

5.5 V

3.9

3.8

4.0 V

3.7

2.7 V

3.6

3.5

-40

-20

0

20

40

60

80

100

Temperature (°C)

279

8159C–AVR–07/09

ATmega8A

Figure 26-56. Calibrated 4 MHz RC Oscillator Frequency vs. VCC

FRC (MHz)

4.1

	-40	°C
4	25	°C
	85	°C

3.9

3.8

3.7

3.6

3.5

2.5

3

3.5

4

4.5

5

5.5

VCC (V)

Figure 26-57. Calibrated 4 MHz RC Oscillator Frequency vs. Osccal Value

	7
																	25 °C
	6
	5
(MHz)	4
RC
F
	3
	2
	1
	0	16	32	48	64	80	96	112	128	144	160	176	192	208	224	240	256

OSCCAL VALUE

280

8159C–AVR–07/09

ATmega8A

Figure 26-58. Calibrated 2 MHz RC Oscillator Frequency vs. Temperature

FRC (MHz)

2.1

2.05

5.5 V

2

1.95

4.0 V

1.9

2.7 V

1.85

1.8

1.75

-40

-20

0

20

40

60

80

100

Temperature (°C)

Figure 26-59. Calibrated 2 MHz RC Oscillator Frequency vs. VCC

FRC (MHz)

	2.1
	2.05	-40 °C
		25 °C
		85 °C

2

1.95

1.9

1.85

1.8

2.5

3

3.5

4

4.5

5

5.5

VCC (V)

281

8159C–AVR–07/09

ATmega8A

Figure 26-60. Calibrated 2 MHz RC Oscillator Frequency vs. Osccal Value

	3																25 °C
	2.5
(MHz)	2
RC
F	1.5
	1
	0.5
	0	16	32	48	64	80	96	112	128	144	160	176	192	208	224	240	256

OSCCAL VALUE

Figure 26-61. Calibrated 1 MHz RC Oscillator Frequency vs. Temperature

FRC (MHz)

1.04

1.02

1	5.5 V

0.98

4.0 V

0.96

0.94

2.7 V

0.92

0.9

-40

-20

0

20

40

60

80

100

Temperature (°C)

282

8159C–AVR–07/09

ATmega8A

Figure 26-62. Calibrated 1 MHz RC Oscillator Frequency vs. VCC

FRC (MHz)

1.04
1.02	-40	°C
	25	°C
1	85	°C

0.98

0.96

0.94

0.92

0,9

2.5

3

3.5

4

4.5

5

5.5

VCC (V)

Figure 26-63. Calibrated 1 MHz RC Oscillator Frequency vs. Osccal Value

	1.6
																	25 °C
	1.4
	1.2
(MHz)	1
RC	0.8
F
	0.6
	0.4
	0.2
	0	16	32	48	64	80	96	112	128	144	160	176	192	208	224	240	256

OSCCAL VALUE

283

8159C–AVR–07/09