SMB239
APPLICATIONS INFORMATION (CONTINUED)
As the temperature changes, the resistance of the
thermistor changes creating a voltage proportional to
temperature. The temperature coefficient or Beta (Β) of
the thermistor must be as close to 4400 as possible to
achieve the maximum temperature accuracy.
NTC THERMISTOR
RESISTANCE
24.9K
10K
25K
61.9K
100K
249K
Table 1: NTC values and associated parallel
resistances.
Internal Thermal Protection
When the die temperature of the SMB239 reaches
approximately 110°C, charge current will be reduced to
prevent further die heating. This internal thermal
protection circuit helps to improve device (and
consequently, system) reliability.
Summit Microelectronics, Inc
2129 3.0 2/23/2009
13
SUMMIT [ SUMMIT MICROELECTRONICS, INC. ]
