LTC2995CUD View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC2995CUD' PDF : 20 Pages View PDF
LTC2995
APPLICATIONS INFORMATION
Temperature Thresholds
The threshold voltages at VT1 and VT2 can be set with
the 1.8V reference voltage (VREF) and a resistive divider
as shown in Figure 5.
VREF = 1.8V
VPTAT
1.8V
RTC
VT2
RTB
VT1
O.8V
RTA
SLOPE =
ηACT
t
mV
K
O
200k T1
T2
Figure 5. Temperature Thresholds
T
L 2995 F05
3.3V
The following design procedure can be used to size the
resistive divider.
1. Calculate Threshold Voltages:
VT1 = T1 • 4 mV • ηACT
K 1.004
VT2 = T2 • 4 mV • ηACT
K 1.004
where ηACT denotes the actual ideality factor if an external
sensor is used and T1 and T2 are the desired threshold
temperatures in degrees Kelvin.
2. Choose RTA to obtain the desired VT1 threshold for
a desired current through the resistive divider
(IREF):
R
TA
=
VT1
IREF
3. Choose RTB to obtain the desired VT2 threshold:
R TB
=
VT2 – VT1
IREF
D+
DS
VREF 1.8V
200k
RTC
400k
VT2
RTB
VT1
VCC
PS
VCC
1.2V
LTC2995
–
+
TO1/TO2
UVLO
PULSE
–
GENERATOR
+
T/V
RTA
VCC
400k
TO2
OT ALARM
VCC
400k
TO1
OT WARNING
VPTAT
D–
GND
2995 F06
Figure 6. Monitoring Internal Temperature with Two Overtemperature Thresholds
2995f
13
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