max2003cse Maxim Integrated Products, Inc., max2003cse Datasheet - Page 8

• Manufacturer Part Number: max2003cse
• Description: Nicd/nimh Battery Fast-charge Controllers Integrated Products
• Manufacturer: Maxim Integrated Products, Inc.

The MAX2003/MAX2003A employs a negative tempera-
ture-coefficient (NTC) thermistor to measure the bat-
tery’s temperature. This temperature value can be used
to determine start and termination of fast-charge. The
two temperature conditions that can be used for fast-
charge termination are:
Figure 5 shows the various temperature cutoff points and
the typical voltages that the device will see at the TS pin.
V
age at TS when the battery temperature is too low, and
V
temperature cutoff. If the voltage is outside these limits,
the MAX2003/MAX2003A will not enter fast-charge
mode. After fast-charge is initiated, the termination
point for high-temperature termination is V
ature cutoff voltage), rather than V
TEMP LED status.
V
V
determine the high-temperature cutoff after fast-charge
begins. V
above V
Thermistors are inherently nonlinear with respect to
temperature. This nonlinearity is especially noticed
when
charge termination. The simplest way around this is to
place a resistor-divider network in parallel with the ther-
mistor (Figure 6) to reduce the effects of nonlinearity.
The lowpass filter (R
ates high-frequency noise on the signal seen by TS.
NiCd/NiMH Battery
Fast-Charge Controllers
Figure 5. Temperature Measurement Scale
8
LTF
HTF
LTF
LTF
_______________________________________________________________________________________
• Maximum Temperature
• Rate-of-Change of Temperature ( T/ t)
(low-temperature fault voltage) refers to the volt-
(high-temperature fault voltage) refers to the high-
is set internally at 0.4V
is 2V. V
TEMP LED
STATUS
TCO
T/ t measurements are made to determine
OFF
ON
ON
HTF
.
TCO
7 / 8 (V
1 / 8 (V
is internally set to be (V
LTF
LTF
is set up using external resistors to
- V
- V
Temperature Measurement
T
, C
TCO
TCO
)
)
T
) placed on the TS pin attenu-
CC
, so (with a 5V supply)
V
V
V
V
V
HTF
CC
LTF
HTF
TCO
SS
= 0V
= 5V
= 0.4V
. See Figure 5 for
LTF
CC
TCO
- V
V
LTF
(temper-
TCO
- V
TCO
) / 8
Before fast-charge is initiated, the cell voltage and tem-
perature of the battery pack must be within the
assigned limits. If the voltage or temperature is outside
these limits, the device is said to be in a “charge-pend-
ing” state. During this mode, the CHG pin will cycle low
(LED on) for 0.125sec and high (LED off) for 1.375sec.
Fast-charge is normally initiated if the cell voltage is
greater than V
voltage is too low (below V
the trickle current brings the voltage up before fast-
charge is initiated. V
(for a 5V supply) V
If the temperature of the cell is not between V
V
Temperature Measurement section).
If the MAX2003/MAX2003A are out of the charge-pend-
ing state, fast-charge can be initiated upon one of the
following conditions:
During fast-charge, the CHG pin will be continuously
low (LED on). For the initial period of fast-charge (the
hold-off time), the voltage charge-termination methods
are disabled. The hold-off time is a function of the
charge rate selected by TM1 and TM2 (see Table 4).
Figure 6. Thermistor Configuration for Temperature Measurement
HTF
• Battery Replacement
• Applying Power to the MAX2003/MAX2003A
• Digital Control Signal
the device is also in a charge-pending state (see
(battery already present)
RT2
RT1
V
CC
EDV
NTC
EDV
(end-of-discharge voltage). If the cell
EDV
is 1V.
RC FILTER
100k
0.1 F
R
is set internally at 0.2V
T
C
T
EDV
Initiate Fast-Charge
), the device waits until
SNS
TS
Charge Pending
MAX2003A
MAX2003
LTF
CC
, so
and