ATTINY13 datasheet(33/177 Pages) ATMEL

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ATtiny13

2535G–AVR–01/07

External Reset

An External Reset is generated by a low level on the RESET pin if enabled. Reset

pulses longer than the minimum pulse width (see Table 12) will generate a reset, even if

the clock is not running. Shorter pulses are not guaranteed to generate a reset. When

the applied signal reaches the Reset Threshold Voltage – V

RST – on its positive edge,

the delay counter starts the MCU after the Time-out period – t

TOUT – has expired.

Figure 16. External Reset During Operation

Brown-out Detection

ATtiny13 has an On-chip Brown-out Detection (BOD) circuit for monitoring the V

CC level

during operation by comparing it to a fixed trigger level. The trigger level for the BOD

can be selected by the BODLEVEL Fuses. The trigger level has a hysteresis to ensure

spike free Brown-out Detection. The hysteresis on the detection level should be inter-

preted as V

BOT+ = VBOT + VHYST/2 and VBOT- = VBOT - VHYST/2.

Note:

1. V

BOT may be below nominal minimum operating voltage for some devices. For

devices where this is the case, the device is tested down to VCC = VBOT during the

production test. This guarantees that a Brown-out Reset will occur before VCC drops

to a voltage where correct operation of the microcontroller is no longer guaranteed.

When the BOD is enabled, and V

CC decreases to a value below the trigger level (VBOT-

in Figure 17), the Brown-out Reset is immediately activated. When V

CC increases above

the trigger level (V

BOT+ in Figure 17), the delay counter starts the MCU after the Time-

out period t

TOUT has expired.

The BOD circuit will only detect a drop in V

CC if the voltage stays below the trigger level

for longer than t

BOD given in Table 14.

Table 13. BODLEVEL Fuse Coding(1)

BODLEVEL [1..0] Fuses

Min V

BOT

Typ V

BOT

Max V

BOT

Units

BOD Disabled

1.8

2.7

4.3

Table 14. Brown-out Characteristics

Symbol

Parameter

Min

Typ

Max

Units

HYST

Brown-out Detector Hysteresis

tBOD

Min Pulse Width on Brown-out Reset

µs

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