LTC3586EUFE#PBF Linear Technology, LTC3586EUFE#PBF Datasheet - Page 27

• Manufacturer Part Number: LTC3586EUFE#PBF
• Description: IC MANAGER USB PWR HI-EFF 38QFN
• Manufacturer: Linear Technology

Specifications of LTC3586EUFE#PBF

• Applications: Handheld/Mobile Devices
• Voltage - Supply: 4.35 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 38-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -

By using a bias resistor, R
R25, the hot and cold trip points can be moved in either
direction. The temperature span will change somewhat due
to the non-linear behavior of the thermistor. The following
equations can be used to easily calculate a new value for
the bias resistor:
where r
sired hot and cold trip points. Note that these equations
are linked. Therefore, only one of the two trip points can
be chosen, the other is determined by the default ratios
designed in the IC. Consider an example where a 60°C
hot trip point is desired.
From the Vishay Curve 1 R-T characteristics, r
0.2488 at 60°C. Using the above equation, R
be set to 46.4k. With this value of R
is about 16°C. Notice that the span is now 44°C rather
than the previous 40°C. This is due to the decrease in
applicaTions inForMaTion
R
R
V
BUS
NOM
NOM
T
R
100k
NOM
HOT
NTC
R
100k
5
NTC
=
=
r
0 536
and r
3 25
COLD
r
HOT
.
.
V
BUS
0.017 • V
0.349 • V
COLD
0.765 • V
•
•
R
R
25
25
BUS
are the resistance ratios at the de-
BUS
BUS
(6a)
LTC3586/LTC3586-1
NOM
–
+
–
+
+
–
NTC BLOCK
, different in value from
NOM
, the cold trip point
TOO_COLD
TOO_HOT
NTC_ENABLE
NOM
3586 F06a
Figure 6. NTC Circuits
should
HOT
is
“temperature gain” of the thermistor as absolute tem-
perature increases.
The upper and lower temperature trip points can be inde-
pendently programmed by using an additional bias resistor
as shown in Figure 6b. The following formulas can be used
to compute the values of R
For example, to set the trip points to 0°C and 45°C with
a Vishay Curve 1 thermistor choose:
the nearest 1% value is 105k:
R1 = 0.536 • 105k – 0.4368 • 100k = 12.6k
the nearest 1% value is 12.7k. The final circuit is shown
in Figure 6b and results in an upper trip point of 45°C and
a lower trip point of 0°C.
R
R
R
V
NOM
1 0 536
NOM
BUS
=
T
R
105k
R1
12.7k
NOM
NTC
R
100k
5
NTC
.
=
=
r
3 266 0 4368
COLD
.
•
2 714
V
R
BUS
0.017 • V
LTC3586/LTC3586-1
.
2 714
0.349 • V
NOM
–
.
0.765 • V
– .
r
HOT
BUS
–
BUS
BUS
r
HOT
•
R
(6b)
NOM
LTC3586/LTC3586-1
25
•
–
+
–
+
+
–
•
100
NTC BLOCK
R R 25
and R1:
k
=
104 2
.
TOO_COLD
TOO_HOT
NTC_ENABLE
k

3586 F06b
3586fb