MC33342 ON Semiconductor, MC33342 Datasheet - Page 5

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

require precise charge termination control to maximize cell
capacity and operating time while preventing overcharging.
Overcharging can result in a reduction of battery life as well
as physical harm to the end user. Since most portable
applications require the batteries to be charged rapidly, a
primary and usually a secondary or redundant charge sensing
technique is employed into the charging system. It is also
desirable to disable rapid charging if the battery voltage or
temperature is either too high or too low. In order to address
these issues, an economical and flexible fast charge controller
was developed.
and protection features that are employed in modern high
performance battery charger controllers that are specifically
designed for Nickel Cadmium and Nickel Metal Hydride
batteries. The device is designed to interface with either
primary or secondary side regulators for easy implementation
of a complete charging system. A representative block diagram
in a typical charging application is shown in Figure 8.
internally connects to a voltage to frequency converter and
Input
DC
Nickel Cadmium and Nickel Metal Hydride batteries
The MC33340/342 contains many of the building blocks
The battery voltage is monitored by the V
Charge
Status
Reg Control
Regulator
R2
R1
Trickle
Fast/
Gate
V
V
sen
sen
1
2
3
Figure 8. Typical Battery Charging Application
R2 + R1
2.0 V
1.0 V
sen
Internal Bias
MC33340, MC33342
input that
V Batt
V sen
Battery
Detect
Frequency
Voltage to
Converter
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INTRODUCTION
– 1
High
Low
V
Gate
F/T
Ck
sen
Gnd
−DV Detect
MC33340 or MC33342
Counter
5
Timer
F/V
4
counter for detection of a negative slope in battery voltage. A
timer with three programming inputs is available to provide
backup charge termination. Alternatively, these inputs can be
used to monitor the battery pack temperature and to set the
over and undertemperature limits also for backup charge
termination.
interface this controller with the external charging circuit.
The first output furnishes a gating pulse that momentarily
interrupts the charge current. This allows an accurate method
of sampling the battery voltage by eliminating voltage drops
that are associated with high charge currents and wiring
resistances. Also, any noise voltages generated by the
charging circuitry are eliminated. The second output is
designed to switch the charging source between fast and
trickle modes based upon the results of voltage, time, or
temperature. These outputs normally connect directly to a
linear or switching regulator control circuit in non−isolated
primary or secondary side applications. Both outputs can be
used to drive optoisolators in primary side applications that
require galvanic isolation. Figure 9 shows the typical charge
characteristics for NiCd and NiMh batteries.
Under
Over
Two active low open collector outputs are provided to
t/T
R
t1
t2
t3
Undervoltage
Lockout
Time/
Temp
Select
Q
R
S
Detect
Temp
Over
Temp
Latch
V
CC
0.7 V
8
2.9 V
V
V
CC
CC
30 mA
30 mA
30 mA
t1/T
t2/T
t3/T
7
6
5
ref
sen
ref
Low
High
Battery
Pack
SW1
SW3
T
SW2
R
NTC
R3
R4