Cypress CY8C24794, AN2309 Two-Cell Battery Charger Firmware, Two-Cell Battery Charger Algorithm

AN2309

Figure 7. Temperature Profile

TDISCH_HOT_STOP

THOT_STOP

THOT_RESTART

TCOLD_RESTART TCOLD_STOP

TDISCH_COLD_STOP

	No Discharge
	No Charge	TBATT
Charge in		Charge in
process		Process

No Discharge

Two-Cell Battery Charger Firmware

The two-cell battery charger firmware is separated into several modules that serve distinct functions, such as performing measurements, regulating the battery charge process and timer functions, implementing the charge and cell-balancing algorithms, checking the charge termination conditions, storing calibration settings into the PSoC device Flash memory, and transmitting debugging data. Most of these modules are described in AN2107, AN2258, and AN2294. Therefore, in this section only the charge and cell- balancing algorithms are described.

Two-Cell Battery Charger Algorithm

The two-cell battery charge algorithm is implemented in the charger firmware as a state machine. The following states are used:

Initialization: Indicates charge process initialization.

Activation: Depicts battery activation charging.

Rapid: Depicts rapid battery charging.

Charge Complete: Indicates that the battery pack is charged completely.

Wait For Temperature: Used to depict the idle state when the battery pack temperature is outside the allowed temperature range.

Error: Indicates that during the charge process an error

has occurred. There are three error types: over-voltage, over-current and stage time-out exceptions.

Discharge: Indicates that the battery pack discharge process and the storage device state are without external power supply.

Full Discharge: Indicates that the battery pack is discharged completely and is not suitable for further use.

The two-cell battery charger state diagram is shown in Figure 8 on page 12.

November 25, 2007 Document No. 001-17394 Rev. *B - 11 -

[+] Feedback