LTC4066 LINER [Linear Technology], LTC4066 Datasheet - Page 21

• Manufacturer Part Number: LTC4066
• Description: USB Power Controller and Li-Ion Linear Charger with Low Loss Ideal Diode
• Manufacturer: LINER [Linear Technology]

APPLICATIONS INFORMATION
Power conscious designs may want to use thermistors
whose room temperature value is greater than 10k. Vishay
Dale has a number of values of thermistor from 10k to
100k that follow the “R-T Curve 2.” Using these directly
in the manor spelled out previously in the NTC Thermistor
section will give temperature trip points of approximately
3°C and 47°C, a delta of 44°C. This delta in temperature
can be moved in either direction by changing the value of
R
both trip points to lower temperatures. Likewise a decrease
in R
higher temperatures. To calculate R
temperature for example, use the following equation:
where R
cold temperature trip point. If you want to shift the trip points
to higher temperatures, use the following equation:
where R
hot temperature trip point.
Here is an example using a 100k R-T Curve 1 Thermistor
from Vishay Dale. The difference between the trip points
is 44°C, from before, and we want the cold trip point to
be 0°C, which would put the hot trip point at 44°C. The
R
NOM
NOM
R
R
R
NOM
NOM
NOM
NOM
needed is calculated as follows:
with respect to R
COLD
HOT
with respect to R
=
=
=
=
R
R
3 266
2 815
0 4086
2 815
2 815
R
.
.
.
COLD
COLD
.
is the resistance ratio of R
.
HOT
is the resistance ratio of R
•
•
•
100
•
R
R
R
NTC
NTC
NTC
k
Ω =
NTC
at
at
at
NTC
25
25
116
25
. Increasing R
°
°
°
will move the trip points to
C
C
C
k
Ω
NOM
NTC
for a shift to lower
NTC
NOM
at the desired
at the desired
will move
The nearest 1% value for R
used to bias the NTC thermistor to get cold and hot trip
points of approximately 0°C and 44°C respectively. To
extend the delta between the cold and hot trip points,
a resistor (R1) can be added in series with R
Figure 3b). The values of the resistors are calculated as
follows:
where R
R
trip points. Continuing the example from before with a
desired hot trip point of 50°C:
The fi nal solution is as shown if Figure 3b where R
121k, R1 = 13.3k and R
Gas Gauge
The extremely low impedance of the ideal diode between
BAT and OUT (typically 50mΩ) allows users to connect
all of their loads to the OUT pin. Such a confi guration puts
the LTC4066/LTC4066-1 in a unique position whereby it
can monitor all of the current that fl ows into and out of the
battery. Two output pins, I
enable users to monitor and integrate the battery current
for a true gas gauge function.
R
R
COLD
1 100
NOM
R
R
=
=
NOM
1
13 3
=
=
=
are the values of R
.
⎛
⎜
⎝
120 8
2 815 0 4086
k
NOM
R
=
2 815 0 4086
k
.
•
Ω
.
COLD
2 815 0 4086
.
⎡
⎢
⎣
R
,
.
⎛
⎜
⎝
0 4086
13 3
COLD
k
is the value of the bias resistor, R
2 815 0 4086
.
– .
Ω
– .
.
–
.
,
LTC4066/LTC4066-1
– .
R
k is nearest
121
0 4086
–
HOT
.
– .
R
k nearest
HOT
=
⎞
⎟
⎠
NTC
•
100
NTC
(
STAT
R
NOM
= 100k at 25°C.
⎞
⎟
⎠
COLD
1
k
2 815 0 4086
1
• .
%
at the desired temperature
• .
.
(
%
and POL, are provided to
(
3 266 0 3602
is 115k. This is the value
3 266 0 3602
–
R
– .
HOT
– .
– .
)
–
R
HOT
)
)
– .
NTC
HOT
0 3602
21
NOM
(see
4066fc
and
=
⎤
⎥
⎦