CDH2D09 View Datasheet(PDF) - Maxim Integrated
Part Name
Description
MFG CO.
'CDH2D09' PDF : 44 Pages View PDF
PMIC with Integrated Charger and
Smart Power Selector for Handheld Devices
Table 8. Trip Temperatures for Different Thermistors
THERMISTOR BETA (ß [K])
RTB (kΩ)
RTP (kΩ)
RTS (kΩ)
Resistance at +25°C [kΩ]
Resistance at +50°C [kΩ]
Resistance at 0°C [kΩ]
Nominal Hot Trip
Temperature [°C]
Nominal Cold Trip
Temperature [°C]
3000
10
Open
Short
10
4.59
25.14
55
-3
3250
10
Open
Short
10
4.30
27.15
53
-1
3500
10
Open
Short
10
4.03
29.32
51
0
3750
10
Open
Short
10
3.78
31.66
49
2
4250
10
Open
Short
10
3.32
36.91
46
5
4250
10
120
Short
10
3.32
36.91
45
0
RTB
ALTERNATE THERMISTOR
CONFIGURATION
RTS
RTP
T
T
VL
CEN
0.74 x VL
THM
COLD
HOT
0.284 x VL
ESD
DIODE
AGND
BOTH COMPARATORS
HAVE 65mV HYSTERESIS
TEMPERATURE
SUSPEND
MAX8671X
Figure 14. Thermistor Input
Since the thermistor monitoring circuit employs an
external bias resistor from THM to VL (RTB in Figure
14), any resistance thermistor can be used as long as
the value of RTB is equivalent to the thermistor’s +25°C
resistance. For example, with a 10kΩ at +25°C thermis-
tor, use 10kΩ at RTB, and with a 100kΩ at +25°C ther-
mistor, use 100kΩ at RTB. The general relation of
thermistor resistance to temperature is defined by the
following equation:
RT
=
R25
×
e⎧⎨⎩β⎛⎝⎜
T
1
+ 273
−
1 ⎞⎫
298 ⎠⎟
⎬
⎭
where:
RT = The resistance in ohms of the thermistor at tem-
perature T in Celsius
R25 = The resistance in ohms of the thermistor at
+25°C
β = The material constant of the thermistor that typically
ranges from 3000K to 5000K
T = The temperature of the thermistor in °C that corre-
sponds to RT
40 ______________________________________________________________________________________
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