LTC4065 LINER [Linear Technology], LTC4065 Datasheet - Page 19

• Manufacturer Part Number: LTC4065
• Description: High Efficiency Battery Charger/USB Power Manager
• Manufacturer: LINER [Linear Technology]

applicaTions inForMaTion
From the Vishay Curve 1 R-T characteristics, r
at 60°C. Using the above equation, R
46.4k. With this value of R
16°C. Notice that the span is now 44°C rather than the
previous 40°C. This is due to the decrease in “temperature
gain” of the thermistor as absolute temperature increases.
The upper and lower temperature trip points can be inde-
pendently programmed by using an additional bias resistor
as shown in Figure 4b. 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:
the nearest 1% value is 12.7k. The final solution is shown
in Figure 4b and results in an upper trip point of 45°C and
a lower trip point of 0°C.
R1 = 0.536 • 105k – 0.4368 • 100k = 12.6k
V
R
R1= 0.536 • R
R
BUS
NOM
NOM
T
R
100k
NOM
NTC
R
100k
1
NTC
=
=
r
3.266 − 0.4368
COLD
V
2.714
BUS
0.349 • V
2.714
0.765 • V
NOM
− r
HOT
0.1V
BUS
− r
BUS
HOT
• R25
NOM
NOM
–
+
–
+
+
–
• 100k = 104.2k
NTC BLOCK
• R25
, the cold trip point is about
LTC4088
and R1:
NOM
should be set to
TOO_COLD
TOO_HOT
NTC_ENABLE
HOT
is 0.2488
4088 F04a
Figure 4. NTC Circuits
USB Inrush Limiting
The USB specification allows at most 10µF of downstream
capacitance to be hot-plugged into a USB hub. In most
LTC4088 applications, 10µF should be enough to provide
adequate filtering on V
the following circuit can be used to soft-connect additional
capacitance.
In this circuit, capacitor C1 holds MP1 off when the cable
is first connected. Eventually the bottom plate of C1 dis-
charges to GND, applying increasing gate support to MP1.
The long time constant of R1 and C1 prevent the current
from building up in the cable too fast, thus dampening
out any resonant overshoot.
V
BUS
T
R
105k
R1
12.7k
NOM
NTC
R
100k
5V USB
1
NTC
INPUT
USB CABLE
V
Figure 5. USB Soft-Connect Circuit
BUS
0.349 • V
0.765 • V
0.1V
BUS
BUS
BUS
. If more capacitance is required,
C1
100nF
–
+
–
+
+
–
NTC BLOCK
LTC4088
Si2333
MP1
R1
40k
LTC4088
C2
TOO_COLD
TOO_HOT
NTC_ENABLE
V
GND
LTC4088
BUS
4088 F05
4088 F04b
19
4088fb