ATTINY25-20SUR Atmel, ATTINY25-20SUR Datasheet - Page 26

• Manufacturer Part Number: ATTINY25-20SUR
• Description: MCU AVR 2KB FLASH 20MHZ 8SOIC
• Manufacturer: Atmel
• Series: AVR® ATtinyr

Specifications of ATTINY25-20SUR

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: USI
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 6
• Program Memory Size: 2KB (1K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 128 x 8
• Ram Size: 128 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 4x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

6.2.1
6.2.2
26
ATtiny25/45/85
External Clock
High Frequency PLL Clock
mal operation. The Watchdog Oscillator is used for timing this real-time part of the start-up time.
The number of WDT Oscillator cycles used for each time-out is shown in
Table 6-2.
To drive the device from an external clock source, CLKI should be driven as shown in
4. To run the device on an external clock, the CKSEL Fuses must be programmed to “00”.
Figure 6-4.
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table
Table 6-3.
When applying an external clock, it is required to avoid sudden changes in the applied clock fre-
quency to ensure stable operation of the MCU. A variation in frequency of more than 2% from
one clock cycle to the next can lead to unpredictable behavior. It is required to ensure that the
MCU is kept in Reset during such changes in the clock frequency.
Note that the System Clock Prescaler can be used to implement run-time changes of the internal
clock frequency while still ensuring stable operation. Refer to
31
There is an internal PLL that provides nominally 64 MHz clock rate locked to the RC Oscillator
for the use of the Peripheral Timer/Counter1 and for the system clock source. When selected as
SUT[1:0]
for details.
00
01
10
11
6-3.
Typ Time-out
Number of Watchdog Oscillator Cycles
External Clock Drive Configuration
Start-up Times for the External Clock Selection
64 ms
Start-up Time from
4 ms
Power-down
6 CK
6 CK
6 CK
EXTERNAL
SIGNAL
CLOCK
Additional Delay from
Reserved
14CK + 64 ms
14CK + 4 ms
CLKI
GND
Reset
14CK
Number of Cycles
“System Clock Prescaler” on page
8K (8,192)
512
BOD enabled
Fast rising power
Slowly rising power
Recommended Usage
Table
6-2.
2586M–AVR–07/10
Figure 6-