2
Atmel AVR365
8336A-AVR-03/12
2 Hardware
The Atmel ATBM302-EK can be divided in two parts: the main area and the
connector area. The main area contains all the components needed in a battery pack.
In the connector area there are four connectors: Cell connector, pack connector, ISP
connector and SMBus connector. Users can connect all the external connections at
these ports. The board size is 100mm × 28.5mm.
Figure 2-1.
Main area and connector area.
2.1 Main area
The main area includes all the components used for the battery pack system in the
top layer and bottom layer. Its size is 80mm × 15mm.
2.1.1 Cell balancing
The ATBM302 IC integrates cell balancing FETs. The chip provides one cell
balancing FET for each battery cell in series.
The on-resistance of the cell balancing FET is about 100
Ω
.
2.1.2 Polarity safety FET
The reverse polarity protection circuit will ensure that the discharge FET (Q3) will turn
off if the charger with reverse polarity connects to the P+ and P-. So the battery can
be ensured to be safe in such cases.
The polarity FET will pull the source of the discharge FET to the negative input
voltage to turn off the discharge FET.
