Datasheet
MCP9509/10
DS22114A-page 12 © 2008 Microchip Technology Inc.
4.4 Sensor Hot/Cold Options
MCP9509/10 is available with Hot (H) and Cold (C)
options. The MCP9509/10 Hot option detects rising
temperature while the Cold option detects falling tem-
perature. The output of the Hot option asserts when
temperature rises above T
SET
and de-asserts when
temperature falls below T
HYST
. The output of the Cold
option asserts when temperature falls below T
SET
and
de-asserts when temperature rises above T
HYST
.
For example, if T
SET
= 100°C for Hot option
(Active-Low Configuration, HYST = V
DD
), output
asserts Low when temperature is greater than
100°C ± T
ACY
. The output de-asserts High when
temperature is below 90°C. For the Cold option, output
asserts Low when temperature is less than
100°C ± T
ACY
, and de-asserts when temperature is
greater than 110°C. This operation is shown graphically
in Figure 4-4.
4.5 R
SET
vs. Temperature
The relation between the user selectable external
resistor R
SET
and the output trigger threshold limit T
SET
is described as shown in EQUATION 4-1: “T
SET
to
R
set
conversion” and EQUATION 4-2: “R
SET
to T
set
conversion”. The equation coeffcients vary depending
on the device output options, H or C. Table 4-1 shows
the corresponding coefficients.
TABLE 4-1: COEFFICIENTS/VARIABLES
EQUATION 4-1: T
SET
TO R
SET
CONVERSION
EQUATION 4-2: R
SET
TO T
SET
CONVERSION
The equations can be used to determine the external
resistance value for a specified temperature threshold
or threshold value for a specified resistance. Table 4-2
and Table 4-3 show a look-up table which can be used
to easily identify the T
SET
to R
SET
relation for Hot and
Cold options.
Coef. MCP9509/10H MCP9509/10C Units
C
R1
-9.84 -10.00 10
-6
kΩ/°C
3
C
R2
3.355 3.345 10
-3
kΩ/°C
2
C
R3
-0.8648 -0.8610 kΩ/°C
C
T1
-20.00 -19.7 10
-6
°C/kΩ
3
C
T2
4.136 4.179 10
-3
°C/kΩ
2
C
T3
-1.1564 -1.1617 °C/kΩ
R
1
94.1 95.1 kΩ
R
2
145.5 146.3 kΩ
R
3
2.77 4.25 kΩ
T
1
-40.0 °C
T
2
125.0 °C
Where:
C
R1,2,3
= 1st, 2nd and 3rd order
Temperature to Resistance
Conversion Coefficients
(Table 4-1)
R
2
= Resistance (Table 4-1)
T
1,2
= Temperature (Table 4-1 )
R
SET
C
R1
T
SET
T
SET
T
1
–()T
SET
T
2
–()+=
C
R2
T
SET
T
1
–()T
SET
T
2
–()+
C
R3
T
SET
T
1
–()R
2
+
Where:
C
C1,2,3
= 1st, 2nd and 3rd order
Resistance to Temperature
Conversion Coefficients
(Table 4-1)
R
1,2,3
= Resistance (Table 4-1)
T
1
= Temperature (Table 4-1 )
T
SET
C
T1
R
SET
R
1
–()R
SET
R
2
–()R
SET
R
3
–()+=
C
T2
R
SET
R
3
–()R
SET
R
2
–()+
C
T3
R
SET
R
2
–()T
1
+