Datasheet

To
TCOLD
NTC
TCOLD
To
HOT
NTC
THOT
1 1
R R e
o
1 1
T
R R e
o
æ ö
ç ÷
ç ÷
è ø
æ ö
ç ÷
ç ÷
è ø
b -
=
b -
=
bq51013B
www.ti.com SLUSB62A –MARCH 2013–REVISED OCTOBER 2013
Where:
(4)
where, T
COLD
and T
HOT
are the desired temperature thresholds in degrees Kelvin. R
O
is the nominal resistance
and β is the temperature coefficient of the NTC resistor. R
O
is fixed at 20 kΩ. An example solution is provided:
• R1 = 4.23kΩ
• R3 = 66.8kΩ
where the chosen parameters are:
• %V
HOT
= 19.6%
• %V
COLD
= 58.7%
• T
COLD
= –10°C
• T
HOT
= 100°C
• β = 3380
• R
O
= 10kΩ
The plot of the percent V
TSB
vs. temperature is shown in Figure 38:
Figure 38. Example Solution for an NTC resistor with R
O
= 10kΩ and β = 4500
Figure 39 illustrates the periodic biasing scheme used for measuring the TS state. The TS_READ signal enables
the TS bias voltage for 24ms. During this period the TS comparators are read (each comparator has a 10 ms
deglitch) and appropriate action is taken based on the temperature measurement. After this 24ms period has
elapsed, the TS_READ signal goes low, which causes the TS-Bias pin to become high impedance. During the
next 35ms (priority packet period) or 235ms (standard packet period), the TS voltage is monitored and compared
to 100mV. If the TS voltage is greater than 100mV then a secondary device is driving the TS/CTRL pin and a
CTRL = ‘1’ is detected.
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