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TEA1103

Fast charge ICs for NiCd and NiMH batteries

Philips Electronics 

Philips Semiconductors

Fast charge ICs for NiCd and NiMH

batteries

Preliminary specification

TEA1103; TEA1103T;

TEA1103TS

If pin RFSH is connected to ground by depressing the

switch, the TEA1103x discharges the battery via an

external transistor connected to pin RFSH. The discharge

current is regulated with respect to the external (charge)

sense resistor (Rsense). End-of-discharge is reached when

the battery is discharged to 1 V per cell. Refreshing the

battery can only be activated during charging of NiCd and

NiMH batteries.

The inhibit mode has the main priority. This mode is

activated when the Vstb input pin is connected to ground.

Inhibit can be activated at any charge/discharge state,

whereby the output control signals will be zero, all LEDs

will be disabled and the charger timings will be set on hold.

Table 1 gives an operational summary.

Table 1 Functionality of program pins

FUNCTION

Inhibit

Refresh

∆T/∆t detection

∆T/∆t and voltage peak detection

Voltage peak detection

Trickle charge at standby

Voltage regulation at standby

FCT

X(1)

not low(2)

floating

high

not low

not low

not low

not low

NTC

X(1)

X(1)

note 3

note 3

note 4

X(1)

note 4

note 3

RFSH

X(1)

low

not low

not low

not low

not low

not low

not low

Notes

1. Where X = don’t care.

2. Not low means floating or high.

3. The NTC voltage has been to be less than 3.3 V, which indicates the presence of an NTC.

4. The NTC voltage is outside the window for NTC detection.

5. Vstb has to be floating or set to a battery regulating voltage in accordance with the specification.

Vstb

low

not low

not low

not low

not low

high

not low

floating(5)

Supply block

The supply block delivers the following outputs:

• A power-on reset pulse to reset all digital circuitry at

battery insertion or supply switch-on. After a general

reset the system will start fast charging the battery.

• A 4.25 V stabilized voltage source (VS) is externally

available. This source can be used to set the thermistor

biasing, to initialize the programs, to supply the external

circuitry for battery voltage based charge indication and

to supply other external circuitry.

• A 4.25 V bias voltage (Vsl) is available for use for more

indication LEDs. This output pin will be zero during the

initialization period at start-up, thus avoiding any

interference of the extra LEDs when initializing.

Charge control

The charge current is sensed via a low-ohmic resistor

(Rsense), see Fig.4. A positive voltage is created across

resistor Rb by means of a current source Iref which is set by

Rref in the event of fast charge and by an internal bias

current source in the event of top-off and trickle charge

(IIB), see Fig.1. The positive node of Rb will be regulated to

zero via error amplifier A1, which means that the voltage

across Rb and Rsense will be the same. The fast charge

current is defined by the following equation:

Ifast × Rsense = Rb × Iref

(1)

The output of amplifier A1 is available at the loop stability

pin LS, consequently the time constant of the current loop

can be set. When Vpeak (NiCd and NiMH) is applied, the

current sensing for the battery voltage will be reduced,

implying that the charge current will be regulated to zero

during:

tsense = 210 × POD × tosc

(2)

Actually battery voltage sensing takes place in the last

oscillator cycle of this period.

1999 Jan 27

7

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