Rainbow-electronics ATmega8HVD Instrukcja Użytkownika Pobierz pdf (Strona 42)

8052B–AVR–09/08

ATmega4HVD/8HVD

Figure 10-7. Black-out Reset with high current consumption at V

REG

10.6 ATmega4HVD/8HVD Start-up Sequence

The Voltage Regulator will not start until it is enabled by the Charger Detect module. Before

this happens the chip will be in Power-off mode and only the Charger Detect module is

enabled. In order for the Charger Detect module to enable the Voltage Regulator, the V

BATT

voltage must exceed the Power-On Threshold, V

POT

. When the voltage at V

BATT

exceeds V

POT

the Voltage Regulator starts up and a Power-On Reset forces the chip into RESET state.

10.6.1 Start-up with one FET connected

During start-up with only one FET (D-FET), cell charging through the body diode of the Dis-

charge FET will start immediately when a charger is connected, even if the chip has not

started yet. The voltage on the BATT pin equals the cell voltage (VFET) plus a diode drop dur-

ing the complete start-up sequence, and will hence increase as the cell is being charged.

A typical start-up sequence for the application is illustrated in Figure 10-8 on page 42.

Figure 10-8. Powering up ATmega4HVD/8HVD (1-FET example)

When V

BATT

reaches the power-on threshold V

POT

, the voltage regulator starts up. This causes

VCC to increase rapidly while CREG is being charged. At the same time the digital part of the

REG

Power-on

Internal Reset

BLOT

Power-offCHIP STATE

POR

BATT

INTERNAL_RESET

TOUT

Reset Active

POT

REG

2.2 V

BLOT, START-UP

BLOD

CHARGER CONNECTED

CHARGER DETECTED

1 2 ... 37 38 39 40 41 42 43 44 45 46 47 ... 167 168

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