AN2390 datasheet(16/42 Pages) STMICROELECTRONICS

16 / 42 page

Evaluation board implementation

AN2390

16/42

Figure 10.

NiMH battery recognition algorithm

Here if the battery current is less than a predefined threshold, switch (Q5) as shown in

Figure 9, is enabled and the battery voltage is measured if the battery voltage is lower than

the certain threshold the battery is considered connected otherwise it is considered not to

be connected to the evaluation board.

2.2.6

Power supply restrictions

The battery characteristics have a direct influence on the choice of the DC power supply.

The supply must be able to drive enough current to charge the battery, even in fast charge

mode.

●

VSUPPLY must be larger than (VCE|SAT + Vdiode + VBAT_MAX + RS* ICONST).

Also the MCU, Buck-Boost DC-DC converter, LED and OpAmp consumption must be taken

into account as well. RS is the sense resistor, indicated as R23 in Figure 6.

In this demo, a DC supply providing 5 V and 2 A is chosen which is sufficient to satisfy the

above condition.

NiMH BATT

Recog Algo

Exit

YES

ENABLE THE SWITCH AND

MEASURE THE BATTERY

VOLTAGE

IF (IBAT > IOPEN)

BATTERY NOT PRESENT

YES

END

BATTERY PRESENT

IF (VBAT > VOPEN)

AN2390 Datasheet(PDF) 16 Page - STMicroelectronics