TEA1104/N2 View Datasheet(PDF) - Philips Electronics

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TEA1104/N2

Cost effective battery monitor and fast charge IC for NiCd and NiMH chargers

Philips Electronics 

Philips Semiconductors

Cost effective battery monitor and fast

charge IC for NiCd and NiMH chargers

Objective specification

TEA1104; TEA1104T

APPLICATION INFORMATION

A guideline for the settings of TEA1104 and its external

components selection is given based on an example of a

1 hour charger for a 4 cell NiCd or NiMH battery pack. The

basic application diagram as illustrated in Fig.6 which is

based on the application diagram illustrated in Fig.7 with

some additional components; a 2 LED charge status

indication has been provided.

For charging a battery within one hour the charge current

rating should be as follows:

Required minimum charge current = battery

capacity × 1.2/charge time.

Therefore, for a 1 Ah battery the external charge current

supply has to deliver at least 1.2 A.

TEA1104 settings

The fast charge back-up timer period, time-out, has to be

set in relation to the expected maximum charge time.

Normally, a safety back-up time is chosen approximately

25% longer than the maximum expected fast charge time.

For a one hour charger the time-out period can be set to

1.25 h.

Time-out relationship with the oscillator repetition time is

as follows;

tosc = time-out (h) × 3600/2 exp28

tosc = 17µs for time-out = 1.25 h

tosc is set with the combination of Cosc and Rref;

where tosc = 0.93 × Rref × Cosc.

Rref can be chosen between 13 and 120 kΩ, but a 27 kΩ

resistor is recommended. The oscillator capacitor can be

calculated which is 668 pF; the nearest higher practical

value is 680 pF.

In the trickle charge mode the LED output will pulsate with

a repetition time; ttrickle = 2 exp14 × tosc = 0.28 s.

The duty factor of the pulse is 2.5% of ttrickle. This duty

factor also applies to the charge current as the charge

current switch is driven by the LED output. Therefore, the

average trickle charge current is Ifast /40. The Vbat input

can be adapted to the battery voltage via the resistor

dividers R1 and R2. When an NTC thermistor has been

incorporated into the battery, the minimum, maximum and

cut-off temperature levels can be set with the resistors R3

and R4. For an NTC with a common sensitivity of 3965

and adjustment resistor values R3 = 13 kΩ, R4 = 20 kΩ

the minimum, maximum and cut-off temperatures will be 5,

42 and 50 °C respectively.

The flow chart of the TEA1104; TEA1104A is given in

Fig.5. The load state of the batteries can be displayed by

one or two LEDs. The flow chart is not to be regarded as

sequential. Each mode of operation is a purely separate

continuous process.

Table 1 Dual LED indication

CHARGER

MODE

VLED

VS

Fast charging

low

high

Fast charging

protection

low/high high

Full

low/high low

(trickle charging)

Battery open

high high

LED 1 LED 2

on

off

on/off off

off

on

off

off

1996 Feb 26

10

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