|TEA1102/N1||Fast charge ICs for NiCd, NiMH, SLA and LiIon|
|TEA1102/N1 Datasheet PDF : 28 Pages |
Fast charge ICs for NiCd, NiMH, SLA and
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.
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
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
tsense = 210 × POD × tosc
Actually battery voltage sensing takes place in the last
oscillator cycle of this period.
To avoid modulation on the output voltage, the top-off
charge current is DC regulated, defined by the following
Itop – off × Rsense = Rb × 3 × 10–6
ttop – off = 227 × TOD × tosc
The top-off charge current will be approximately 0.15 CA,
which maximizes the charge in the battery under safe and
slow charging conditions. The top-off charge period will be
approximately one hour, so the battery will be extra
charged with approximately 0.15 Q. In this way the battery
is fully charged before the system switches over to
When pin 1 (Vstb) is connected to VS, or no NTC is
connected the system compensates the (self) discharge of
the battery by trickle charge. The trickle charge current will
be pulsating, defined by the following equation:
Itrickle × Rsense = Rb × 11----56-- × 10–6
During the non current periods at trickle charge the charge
current is regulated to zero, so that the current for a load
connected in series across the battery with the sense
resistor will be supplied by the power supply and not by the
If at pin 1 (Vstb) a reference voltage is set in accordance
with the specification, and no NTC is connected the charge
mode will switch over from current to voltage regulation
after top-off. The reference regulating voltage can be
adjusted to the battery characteristic by external resistors
connected to pin Vstb.
This reference voltage has to be selected in such a way
that it equals the rest voltage of the battery. By using
voltage regulation, the battery will not be discharged at a
load occurrence. If the Vstb input pin is floating, the
TEA1102x will apply voltage regulation at 1.325 V during
the standby mode (NiCd and NiMH). The current during
voltage regulation is limited to 0.5 CA. If the battery charge
current is maximized to 0.5 CA for more than 2 hours
charging will be stopped. Moreover, if the temperature
exceeds Tmax, charging will be stopped completely.
As voltage regulation is referred to one cell, the voltage on
the Vbat pin must be the battery voltage divided by the
number of cells (NiCd and NiMH).
For LiIon or SLA batteries, the battery is extra charged
after full detection by constant voltage regulation during a
certain fill-up period. LiIon and SLA batteries have to
identify themselves by an extra pin on the battery pack to
ground, which is connected via a resistor to pin 11 (FCT).
As the battery voltage sense (Vbat) has to be normalized to
a one cell voltage of NiCd and NiMH packages, the Vbat
input pin will be regulated to 1.367 and 1.633 V during
fill-up for LiIon and SLA respectively. In this way this
system can accept a mixture of one LiIon, two SLA and
three NiCd or NiMH packages.
After fill-up, charging of LiIon or SLA batteries is disabled.
The battery charge is then fixed to zero, ensuring
maximum life-cycle of the battery.
Because of a fixed zero charge current, the battery will be
discharged if a load is applied.
1999 Jan 27
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