Rainbow-electronics ATmega8HVD Manuel d'utilisateur télécharger pdf (Page 144)

144

8052B–AVR–09/08

ATmega4HVD/8HVD

26.3 System and Reset Characteristics

Notes: 1. Values are guidelines only. Actual values are TBD.

2. Not tested in production.

3. The ATmega4HVD/8HVD will start up when the voltage at the BATT pin exceeds V

POT

4. The BATT pin monitors the charger voltage. Because of the voltage drop across the body diode of the Discharge FET, the

supply voltage at the VFET pin is approximately 0.5V below the V

POT

level when the ATmega4HVD/8HVD starts up. That is

why typical V

POT

level is set to 3.0V.

5. V

BLOT

may be below nominal minimum operating voltage for some devices. For devices where this is the case, the device is

tested down to V

REG

= V

BLOT, NORMAL

during the production test. This guarantees that a Black-out Reset will occur before V

drops to a voltage where correct operation of the microcontroller is no longer guaranteed. The Black-out detector monitors

the output voltage of the regulator, VREG. V

BLOT

level is therefore not directly related to the V

POT

level.

6. In normal operation, the BLOD detection level will always be lower than the minimum voltage regulator output voltage when

the voltage regulator is operated within its specifications.

26.4 External Interrupts Characteristics

Table 26-2. Power-on, Reset, BLOD, and Voltage Reference Characteristics

(1)

, T

= -20°C to 85°C, VFET = 2.4 to 4.2V

(unless otherwise noted)

Symbol Parameter Condition Min Typ Max Units

POT

Power-on Threshold Voltage

(3)

2.5 3.0

(4)

3.4 V

RST

RESET Pin Threshold Voltage VREG = 2.2V 0.4 1.9 V

RST

Minimum pulse width on RESET Pin

(2)

900 ns

BLOT, NORMAL

BLOD Threshold Voltage

(5)(6)

1.7 1.8 2.0 V

BLOT, START-UP

BLOD Threshold Voltage 2.3 2.5 V

BLOD

Min Pulse Width on Black-out Reset

(2)

2µs

BLODTOUT

Black-out Power-off Delay

(2)

4CK

REF

Bandgap reference voltage after calibration 1.03 1.1 1.17 V

Table 26-3. Asynchronous External Interrupt Characteristics, T

= -20°C to 85°C, VFET = 2.4 to 4.2V (unless otherwise

noted)

Symbol Parameter Condition Min Typ Max Units

INT

Minimum pulse width for asynchronous external

interrupt

50 ns

1 2 ... 139 140 141 142 143 144 145 146 147 148 149 ... 167 168

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