Cypress AN2309, CY8C29x66, CY8C24794 specifications Two-Cell Battery Charger State Diagram

AN2309

Figure 8. Two-Cell Battery Charger State Diagram

Initialization 10

7

1

6

9

13

Activation	Wait For	Discharge
	Temperature

		4
8	2	11	12
	Rapid	5	Full
		Error

Discharge

3

Charge

Complete

Initially the charger is in the Initialization state. After some device preparation, the charger goes to the Activation state (1). When the battery voltage reaches the rapid start voltage, the charger leaves the Activation state and switches to the Rapid state (2). If the charge current drops below a predefined charge-terminate level, the charger goes to the Charge Complete (3) state. The charger remains in the Charge Complete state and the charging process can be restarted if the voltage drops below some predefined level (8). The charging process can be terminated with an error if a total charge time-out or an operation charge time- out occurs, or if the battery voltage or charge current is higher than the charge termination voltage/current levels (4),

(5).

The charger from all states jumps to the Wait For Temperature state when the battery temperature is outside the allowed temperature range. For the Activation and Rapid states, the allowed temperature range is the charge range. For other states, the allowed temperature range is the discharge range (6). In the case of the charge range, when temperatures fall into the defined range with some hysteresis value, the charger goes to the Initialization state

(7).

Regardless of the state of the charger, it jumps to the Discharge state when the external power supply is switched off (9). If the external power supply is switched on, the charger goes to the Initialization state (10, 13). When the battery pack discharges completely (11), the charger switches to the Full Discharge state.

If the system load resistance decreases and the battery pack voltage level re-establishes to the predefined voltage level, then the charger returns to the Discharge state (12).

A two-cell battery charger firmware flowchart that corresponds to the state diagram is shown in Figure 9 on page 13 and Figure 10 on page 14. The invocation points of the cell-balancing procedures are also shown. The charge profile example is presented in the Appendix, Figure 13 on page 18.

November 25, 2007 Document No. 001-17394 Rev. *B - 12 -

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