QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 783

NIMH/NICD CHARGER

6

For higher power dissipation or higher charge cur-

rent situations, an external PNP pass transistor

mounted on a heat sink and, if needed, a current

sense resistor can be added to the demo circuit.

Lift the emitter and base connections to the on-

board transistor when an external transistor is

used. Pads for an external current sense resistor

(R5) are included on this pc board. This resistor is

in parallel with the internal sense resistor and is

selected to have approx 100mV from Vcc to SENSE

at the programmed charge current.

Other time periods can be programmed by adding a

suitable capacitor on the TIMER terminal.

Please refer to the LTC4060 data sheet for addi-

tional information.

DIFFERENCES

BETWEEN

NiCd

AND

NiMH

BATTERIES:

NiCd batteries exhibit very little temperature rise

during most of the charge cycle. The temperature

rise mainly occurs near the end of the charge cycle.

NiMH batteries are different in this respect, where

the battery temperature rise continues during the

charge cycle and accelerates near the end of the

charge cycle.

The - V that occurs when charging a NiMH battery

is less than a NiCd. This makes - V termination

somewhat more difficult to detect for a NiMH bat-

tery.

Figure 2. Optional Demo Board Features