INTEGRATED CIRCUITS
DATA SHEET
TEA1104; TEA1104T
Cost effective battery monitor and fast charge IC for NiCd and NiMH chargers
Objective specification |
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1996 Feb 26 |
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File under Integrated Circuits, IC03 |
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Philips Semiconductors |
Objective specification |
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Cost effective battery monitor and fast
TEA1104; TEA1104T
charge IC for NiCd and NiMH chargers
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
SYMBOL |
PARAMETER |
CONDITIONS |
MIN. |
TYP. |
MAX. |
UNIT |
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VP |
supply voltage |
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5.45 |
− |
11.5 |
V |
IP |
supply current |
outputs off |
− |
− |
3 |
mA |
Vbat |
voltage range of battery full detection |
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0.81 |
− |
3.6 |
V |
Vbat/Vbat |
voltage peak detection level with |
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0.25 |
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% |
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respect to top value |
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Ibat |
battery monitor input current |
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− |
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1 |
nA |
Vbat(l) |
battery voltage protection low |
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− |
0.81 |
0.91 |
V |
Vbat(h) |
battery voltage protection high |
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3.5 |
3.6 |
− |
V |
fosc |
oscillator frequency |
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10 |
− |
100 |
kHz |
ORDERING INFORMATION
TYPE |
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PACKAGE |
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NUMBER |
NAME |
DESCRIPTION |
VERSION |
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TEA1104 |
DIP8 |
plastic dual in-line package; 8 leads (300 mil) |
SOT97-1 |
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TEA1104T |
SO8 |
plastic small outline package; 8 leads; body width 3.9 mm |
SOT96-1 |
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1996 Feb 26 |
2 |
Philips Semiconductors |
Objective specification |
|
|
Cost effective battery monitor and fast
TEA1104; TEA1104T
charge IC for NiCd and NiMH chargers
BLOCK DIAGRAM
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Rref |
VS |
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5 |
3 |
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VP |
6 |
SUPPLY |
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battery high |
POR |
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protection |
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OR |
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8 |
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fast |
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LED |
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trickle |
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FILTER |
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MODE |
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CONTROL |
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LATCH |
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4 |
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1 |
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Vbat |
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GND |
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SAMPLE- |
BATTERY |
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FULL |
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AND-HOLD |
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battery low |
DETECTOR |
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TO |
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protection |
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OR |
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trickle |
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Tmax |
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TIMER |
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Tmin |
TEA1104 |
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TEA1104T |
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Tcut-off |
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OSCILLATOR |
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2 |
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7 |
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MGE354 |
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NTC |
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OSC |
Fig.1 Block diagram.
1996 Feb 26 |
3 |
Philips Semiconductors |
Objective specification |
|
|
Cost effective battery monitor and fast
TEA1104; TEA1104T
charge IC for NiCd and NiMH chargers
PINNING
SYMBOL |
PIN |
DESCRIPTION |
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GND |
1 |
ground |
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NTC |
2 |
negative temperature coefficient |
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resistor input |
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VS |
3 |
stabilized supply voltage |
Vbat |
4 |
battery voltage sensing |
Rref |
5 |
reference resistor |
VP |
6 |
positive supply voltage |
OSC |
7 |
oscillator input |
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LED |
8 |
LED output |
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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
handbook, halfpage
GND |
1 |
8 |
LED |
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NTC |
2 |
7 |
OSC |
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Vs |
3 |
TEA1104 |
VP |
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6 |
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Vbat |
4 |
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5 |
Rref |
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MGE353 |
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Fig.2 Pin configuration.
∙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 VP 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 Rref), a reference current is obtained which defines the accuracy of all IC timing characteristics
∙Externally available 4.25 V stabilized voltage source
(Vsource). 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
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
∙Power-on reset pulse resets all digital circuitry after a start or restart, due to an interrupted VS.
1996 Feb 26 |
4 |
Philips Semiconductors |
Objective specification |
|
|
Cost effective battery monitor and fast
TEA1104; TEA1104T
charge IC for NiCd and NiMH chargers
Open battery protection
When the rechargeable battery is removed, the output voltage Vbat 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
(Vbat > 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 Vbat (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 (Vpeak), 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 Vbat = 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: tosc = K ´ Rref ´ Cosc
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 ´ tosc
·The duty factor in the trickle charge mode: The duty factor is fixed to 1¤40, meaning that the average:
–Itrickle = 1¤40 ´ Ifast
–ton = 3¤4 ´ 2 exp9 ´ tosc
–toff = 2 exp14 ´ tosc.
·The battery voltage is sensed each ‘cycle time’. The cycle time is defined as:
–Tcycle = 2 exp16 ´ tosc
·The ‘inhibit time’ is the time that the charger current is disabled, after which the battery voltage is sensed in a currentless way.
–tinhibit = 10 ´ tosc
Battery sampling takes one oscillator period for each cycle interval.
–tsample = 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.
–tdisable = 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 Rref.
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.
1996 Feb 26 |
5 |
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