MC33342 ON Semiconductor, MC33342 Datasheet - Page 8

• Manufacturer Part Number: MC33342
• Description: (MC33340 / MC33342) Battery Fast Charge Controllers
• Manufacturer: ON Semiconductor

switching between the fast and trickle modes as the lower
temperature limit is crossed. The amount of temperature rise
to overcome the hysteresis is determined by the thermistor’s
rate of resistance change or sensitivity at the under
temperature trip point. The required resistance change is:
of 2°C with a 10 kW thermistor operating at 0°C. The under
temperature fast charge inhibit feature can be disabled by
biasing the t3/T
that present at t2/T
extremely cold conditions, it is possible that the thermistor
resistance can become too high, allowing the t2/T
to go above V
condition can be prevented by placing a resistor in parallel
with the thermistor. Note that the time/temperature
threshold of V
temperature. Refer to the Electrical Characteristics table
and to Figure 4 for additional information.
temperature condition. When the upper temperature limit is
exceeded, the comparator output sets the Overtemperature
Latch and the charger is switched to trickle mode. Once the
latch is set, the charger cannot be returned to fast charge,
even after the temperature falls below the limit. This feature
prevents the battery pack from being continuously
temperature cycled and overcharged. The latch can be reset
Table 1. FAST CHARGE BACKUP TERMINATION TIME/TEMPERATURE LIMIT
The resistance change approximates a thermal hysteresis
The upper comparator senses the presence of an over
DR(T
Low
Termination
Temperature
Backup
Mode
³ T
Time
Time
Time
Time
Time
Time
Time
ref
CC
CC
High
Low input to a voltage that is greater than
sen
− 0.7 V, and activate the timer. This
− 0.7 V is a typical value at room
) +
, and less than V
V H(T)
I
in
0 V to V
+ 44 mV
t3/T
30 mA
(Pin 5)
Open
Open
Open
Open
CC
GND
GND
GND
ref
CC
Low
− 0.7 V. Under
− 0.7 V
+ 1.46 k
MC33340, MC33342
sen
http://onsemi.com
input
Programming Inputs
0 V to V
8
t2/T
(Pin 6)
Open
Open
Open
Open
GND
GND
GND
CC
by removing and reconnecting the battery pack or by cycling
the power supply voltage.
temperature backup features, they can both be easily
disabled. This is accomplished by biasing the t3/T
input to a voltage greater than t2/T
t1/T
Select comparator output is low, indicating that the
temperature mode is selected, and that the t2/T
biased within the limits of an artificial temperature window.
tool applications typically use temperature as the only
means for fast charge termination. The MC33340/342 can
be configured in this manner by constantly resetting the −DV
detection logic. This is accomplished by biasing the V
input to ≈1.5 V from a two resistor divider that is connected
between the positive battery pack terminal and ground. The
V
each time that the Sample Timer causes the V
low, the V
threshold of 1.0 V. This causes a reset of the −DV logic every
1.38 seconds, thus disabling detection.
Operating Logic
by the logic circuitry. Each event is dependent upon the input
conditions and the chosen method of charge termination. A
table summary containing all of the possible operating
modes is shown in Table 2.
sen
sen
If the charger does not require either the time or
Charging of battery packs that are used in portable power
The order of events in the charging process is controlled
− 0.7 V
ref
Gate output is also connected to the V
High input. Under these conditions, the Time/Temp
sen
input will be pulled below the undervoltage
0 V to V
t1/T
(Pin 7)
Open
Open
Open
Open
GND
GND
GND
ref
CC
High
− 0.7 V
sen
, and by grounding the
Timer Disabled
Fast Charge
Time Limit
(Minutes)
sen
sen
283
247
212
177
141
106
71
input. Now,
output to go
sen
ref
input is
Low
sen