Philips TEA1104T-N2, TEA1104-N2, TEA1104-N1 Datasheet

DATA SH EET

Objective speciﬁcation File under Integrated Circuits, IC03

1996 Feb 26

INTEGRATED CIRCUITS

TEA1104; TEA1104T

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

1996 Feb 26 2

Philips Semiconductors Objective speciﬁcation

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

TEA1104; TEA1104T

FEATURES

• Accurate detection of fully charged batteries by currentless peak voltage sensing

• Switch-over from fast to safe trickle charge current at battery full detection

• Fast charge termination back-up by maximum time and maximum temperature detection

• Several trickle charge drive possibilities for mains isolated and non-mains isolated systems

• Battery checking to protect against short-circuited and open batteries

• Battery monitor allows recharging of different battery packs in the same charger

• Dual LED indicator provision

• External regulator not required because of large input

voltage range

• Few low cost external components required.

APPLICATIONS

• Portable telephone

• Portable computer

• Portable audio

• Portable video.

GENERAL DESCRIPTION

The TEA1104 is manufactured in a BiCMOS process intended to be used as a battery monitor circuit in charge systems for NiCd and NiMH batteries. It is especially designed for cost effective compact consumer applications.

The circuit is able to detect fully charged batteries by currentless battery voltage sensing. Several output drive functions are available to control the (reduced) trickle charge current to keep the batteries full with maximum life expectations.

The battery full detection is backed up by two independent mechanisms to make the system fail safe; maximum time and maximum temperature.

QUICK REFERENCE DATA

ORDERING INFORMATION

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

supply voltage 5.45 − 11.5 V

supply current outputs off −−3mA

bat

voltage range of battery full detection 0.81 − 3.6 V

∆V

bat/Vbat

voltage peak detection level with respect to top value

− 0.25 − %

bat

battery monitor input current −−1nA

bat(l)

battery voltage protection low − 0.81 0.91 V

bat(h)

battery voltage protection high 3.5 3.6 − V

osc

oscillator frequency 10 − 100 kHz

TYPE

NUMBER

PACKAGE

NAME DESCRIPTION VERSION

TEA1104 DIP8 plastic dual in-line package; 8 leads (300 mil) SOT97-1

TEA1104T SO8 plastic small outline package; 8 leads; body width 3.9 mm SOT96-1

1996 Feb 26 3

Philips Semiconductors Objective speciﬁcation

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

TEA1104; TEA1104T

BLOCK DIAGRAM

handbook, full pagewidth

MGE354

SAMPLE-

AND-HOLD

FILTER

BATTERY

FULL

DETECTOR

SUPPLY

MODE

LATCH

OSCILLATOR

TIMER

fast

trickle

CONTROL

battery high

protection

battery low

protection

max

min

cut-off

trickle

ref

bat

NTC OSC

LED

GND

POR

TEA1104

TEA1104T

Fig.1 Block diagram.

1996 Feb 26 4

Philips Semiconductors Objective speciﬁcation

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

TEA1104; TEA1104T

PINNING

SYMBOL PIN DESCRIPTION

GND 1 ground NTC 2 negative temperature coefficient

resistor input

3 stabilized supply voltage

bat

4 battery voltage sensing

ref

5 reference resistor

6 positive supply voltage OSC 7 oscillator input LED 8 LED output

Fig.2 Pin configuration.

handbook, halfpage

1 2 3 4

8 7 6 5

MGE353

TEA1104

LED OSCNTC V

ref

bat

GND

INTRODUCTION

The operation of the TEA1104; TEA1104T is explained with the aid of the application diagram illustrated in Fig.7.

An application note (AN95085) is available describing the versatility of the TEA1104; TEA1104T.

An external power current source charges the batteries via an electronic switch which is controlled by the TEA1104. The TEA1104 monitors the battery voltage. Fully charged batteries are detected when the battery voltage peaks. In fact, a voltage drop of 0.25% with respect to the top value is detected. Fast charging is initiated at ‘power on’ or at ‘replaced batteries’. The switch is continuously on, providing that all protection levels are met. At battery full detection, the charge current is duty cycled to reduce the average charge current to a lower level, keeping the batteries fully charged but at he same time assuring long battery life. In Fig.3 the battery voltage during fast charge is plotted.

FUNCTIONAL DESCRIPTION

A block diagram of the TEA1104; TEA1104T is illustrated in Fig.1

Mode latch

The Mode latch determines if the system is in the fast or in the slow charge mode.

• Fast charge is active at: – power switch-on and battery connected – temperature between minimum and maximum value – battery insert

• Trickle charge is active if: – battery full is detected – maximum time is exceeded – maximum cut-off temperature is exceeded after the

initial phase.

Supply block

For correct start-up, the IC supply current is limited to 35 µA (typ.) until the start-up voltage of 6.4 V is reached (standby mode). Thereafter, the operating supply voltage V

has to be within the window of 5.45 to 11.5 V, meaning that there is no need for an external voltage regulator to supply the IC.

The supply block delivers the following outputs:

• With the help of an external resistor (pin R

ref

), a reference current is obtained which defines the accuracy of all IC timing characteristics

• Externally available 4.25 V stabilized voltage source (V

source

). This source is used internally to supply a large part of the circuit and can be used to set the NTC biasing and to supply other external circuitry with a maximum current of 1 mA. Protection information is provided via VS, to design a dual LED indicator

• Power-on reset pulse resets all digital circuitry after a start or restart, due to an interrupted VS.

1996 Feb 26 5

Philips Semiconductors Objective speciﬁcation

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

TEA1104; TEA1104T

Open battery protection

When the rechargeable battery is removed, the output voltage V

bat

will rise to a high level. The ‘open battery protection’ block will detect this voltage and the charge current will be switched off. A digital filter prevents false open battery protection. The open battery signal (V

bat

> 3.6 V) must be present for a duration of at least

4 clock pulses.

Battery monitor

One or two cell packs can be connected directly to V

bat

(battery connection) without an external resistor divider. At larger cell packs the battery voltage must be scaled down to a voltage range of 0.81 to 3.6 V. It is also possible to take a tap on the chain of batteries. Battery full is recognized by voltage peak detection (V

peak

), meaning a decrease of 0.25% (typ.) with respect to the top value. Keeping in mind a battery voltage range of 0.81 to 3.6 V and an accuracy of 10% at V

bat

= 2.4 V for battery full detection, means that the internal ADC has to be 13 bits. Several filters are included to prevent false full detection. The series resistance of the battery and battery connection can cause battery voltage fluctuations and therefore it is necessary to stop the charging before sensing; this is called the ‘inhibit time’. This will be performed automatically via the regulation output pin LED. The charging is stopped for ten oscillator periods at the end of which sampling is performed. The battery voltage will now be sensed in a currentless way.

Timer/oscillator

The oscillator has a sawtooth shape. The period time is defined by: t

osc

=K×R

ref

× C

osc

The oscillator frequency is used in the timer block. In this block several important signals are created.

• Time-out for protecting the fast charge process in time.

Time-out is normally chosen to be 25% longer than the associated fast charge time. So for a one hour charge time, time-out = 1.25 hours. The relationship with the oscillator period time is:

– Time-out = 2 exp28 × t

osc

• The duty factor in the trickle charge mode: The duty

factor is fixed to1⁄40, meaning that the average: –I

trickle

=1⁄40× I

fast

–ton=3⁄4× 2 exp9 × t

osc

–t

off

= 2 exp14 × t

osc

• The battery voltage is sensed each ‘cycle time’. The cycle time is defined as:

–T

cycle

= 2 exp16 × t

osc

• The ‘inhibit time’ is the time that the charger current is disabled, after which the battery voltage is sensed in a currentless way.

–t

inhibit

=10×t

osc

Battery sampling takes one oscillator period for each cycle interval.

–t

sample=tosc

• The ‘disable time’ is present to correct start-up with flat or polarized batteries. During the disable time, the battery full detection is not active.

–t

disable

= 2 exp −5 × time-out

The timer is reset by battery full detection, but is on hold during the temperature and battery-low protection modes.

Temperature protection block

Temperature sensing is achieved by using a cheap thermistor. Two temperature windows are built in:

• If the temperature at power-on reset is above the maximum temperature protection level, the trickle charge current is active. The same applies for temperatures below the minimum temperature. Fast charging starts when the temperature is in between the minimum and the maximum temperature levels.

• If the temperature is between the maximum and minimum temperature at power-on reset, the fast charge current level is active. If the temperature sinks below the minimum temperature level, again the trickle charge level is active. At rising temperature, the fast charge current is latched off at the ‘cut off’ temperature level.

To avoid switching on and off with temperature, a hysteresis is built in for low temperature level. If the temperature protection is not necessary, pin ‘Negative Temperature Coefficient resistor’ (NTC) must be connected to pin R

ref

Battery low protections

When the battery voltage is less than 0.81 V, the circuit assumes that there are short circuited batteries and the charge current is reduced to the trickle charge level. If the batteries are flat, the trickle charge current is able to raise the battery voltage within an acceptable period of time, after which fast charging starts.

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