tea1104.pdf

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INTEGRATED CIRCUITS
DATA SHEET
TEA1104; TEA1104T
Cost effective battery monitor and
fast charge IC for NiCd and NiMH
chargers
Objective specification
File under Integrated Circuits, IC03
1996 Feb 26
11018300.040.png
Philips Semiconductors
Objective specification
Cost effective battery monitor and fast
charge IC for NiCd and NiMH chargers
TEA1104; TEA1104T
FEATURES
APPLICATIONS
·
Accurate detection of fully charged batteries by
currentless peak voltage sensing
·
Portable telephone
·
Portable computer
·
Switch-over from fast to safe trickle charge current at
battery full detection
·
Portable audio
·
Portable video.
·
Fast charge termination back-up by maximum time and
maximum temperature detection
GENERAL DESCRIPTION
·
Several trickle charge drive possibilities for mains
isolated and non-mains isolated systems
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.
·
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.
QUICK REFERENCE DATA
SYMBOL
PARAMETER
CONDITIONS
MIN.
TYP.
MAX.
UNIT
V P
supply voltage
5.45
-
11.5
V
I P
supply current
outputs off
-
-
3
mA
V bat
voltage range of battery full detection
0.81
-
3.6
V
D V bat /V bat
voltage peak detection level with
respect to top value
-
0.25
-
%
I bat
battery monitor input current
-
-
1
nA
V bat(l)
battery voltage protection low
-
0.81
0.91
V
V bat(h)
battery voltage protection high
3.5
3.6
-
V
f osc
oscillator frequency
10
-
100
kHz
ORDERING INFORMATION
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
2
11018300.041.png
Philips Semiconductors
Objective specification
Cost effective battery monitor and fast
charge IC for NiCd and NiMH chargers
TEA1104; TEA1104T
BLOCK DIAGRAM
handbook, full pagewidth
R ref
V S
5
3
V P
6
SUPPLY
battery high
protection
POR
OR
fast
trickle
8
LED
FILTER
MODE
LATCH
CONTROL
4
1
V bat
GND
SAMPLE-
AND-HOLD
BATTERY
FULL
DETECTOR
battery low
protection
TO
OR
trickle
T max
TIMER
T min
TEA1104
TEA1104T
T cut-off
OSCILLATOR
2
7
MGE354
NTC
OSC
Fig.1 Block diagram.
1996 Feb 26
3
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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
handbook, halfpage
GND
1
8
LED
NTC
2
negative temperature coefficient
resistor input
NTC
2
7
OSC
TEA1104
V S
3
stabilized supply voltage
V s
3
6
V P
R ref
V bat
4
battery voltage sensing
V bat
4
5
R ref
5
reference resistor
MGE353
V P
6
positive supply voltage
OSC
7
oscillator input
Fig.2 Pin configuration.
LED
8
LED output
INTRODUCTION
·
Trickle charge is active if:
– battery full is detected
– maximum time is exceeded
– maximum cut-off temperature is exceeded after the
initial phase.
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.
Supply block
A (typ.) until the start-up voltage of 6.4 V is reached
(standby mode). Thereafter, the operating supply voltage
V P 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.
m
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
V S , to design a dual LED indicator
FUNCTIONAL DESCRIPTION
A block diagram of the TEA1104; TEA1104T is illustrated
in Fig.1
Mode latch
·
Power-on reset pulse resets all digital circuitry after a
start or restart, due to an interrupted V S .
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
1996 Feb 26
4
For correct start-up, the IC supply current is limited to
35
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Philips Semiconductors
Objective specification
Cost effective battery monitor and fast
charge IC for NiCd and NiMH chargers
TEA1104; TEA1104T
Open battery protection
·
The battery voltage is sensed each ‘cycle time’. The
cycle time is defined as:
–T cycle = 2 exp16 ´ t osc
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.
·
The ‘inhibit time’ is the time that the charger current is
disabled, after which the battery voltage is sensed in a
currentless way.
– inhibit =10
t osc
Battery sampling takes one oscillator period for each
cycle interval.
– sample =t osc
· 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.
– 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.
´
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.
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 .
Timer/oscillator
C osc
The oscillator frequency is used in the timer block. In this
block several important signals are created.
·
´
R ref ´
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
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.
·
The duty factor in the trickle charge mode: The duty
factor is fixed to 1
¤ 40 , meaning that the average:
– trickle = 1
¤ 40 ´
I fast
¤ 4 ´ 2 exp9 ´ t osc
– off = 2 exp14
´
t osc .
1996 Feb 26
5
·
The oscillator has a sawtooth shape.
The period time is defined by: t osc =K
– on = 3
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