Datasheet

LTC2995
13
2995f
D
+
DS
D
–
1.2V
200k
400k
1.8V
V
CC
V
REF
R
TC
VT2
VT1
V
CC
V
PTAT
PS
TO2
TO1
3.3V
LTC2995
2995 F06
OT ALARM
OT WARNING
R
TB
R
TA
GND
–
+
–
+
–
+
TO1/TO2
PULSE
GENERATOR
UVLO
V
CC
400k
V
CC
400k
T/V
Figure 5. Temperature Thresholds
Figure 6. Monitoring Internal Temperature with Two Overtemperature Thresholds
APPLICATIONS INFORMATION
Temperature Thresholds
The threshold voltages at VT1 and VT2 can be set with
the 1.8V reference voltage (V
REF
) and a resistive divider
as shown in Figure 5.
The following design procedure can be used to size the
resistive divider.
1. Calculate Threshold Voltages:
VT1 = T1• 4
mV
K
•
η
ACT
1.004
VT2 = T2 • 4
mV
K
•
η
ACT
1.004
where η
ACT
denotes the actual ideality factor if an ex ternal
sensor is used and T1 and T2 are the desired threshold
temperatures in degrees Kelvin.
2. Choose R
TA
to obtain the desired VT1 threshold for
a desired current through the resistive divider
(I
REF
):
R
TA
=
VT1
I
REF
3. Choose R
TB
to obtain the desired VT2 threshold:
R
TB
=
VT2 – VT1
I
REF
2995 F05
V
PTAT
R
TC
R
TB
R
TA
V
REF
= 1.8V
1.8V
SLOPE = t

ACT
η
O
T
200k T
1
T
2
L
VT2
VT1
O.8V
K
mV