Datasheet

MCP9501/2/3/4
DS22268A-page 8 © 2011 Microchip Technology Inc.
4.0 FUNCTIONAL DESCRIPTION
The MCP9501/2/3/4 temperature switch family
integrates a thermal diode, a comparator, and a factory
selectable resistive network used to set the
temperature thresholds. The available output
thresholds range from -35°C to 125°C at 10°C
increments. There is no additional configuration
required to operate this device. The selectable output
hysteresis is controlled using a single input pin. When
this pin is connected to ground, the output hysteresis is
2°C (typical) and when connected to V
DD
the output
hysteresis is 10°C (typical). Figure 4-1 shows the
functional block diagram.
FIGURE 4-1: Functional Block Diagram.
There are two output configurations for this family, a
push-pull and an open-drain output with active-high
and active-low assertions. These assertion options are
referred to as Cold and Hot options, primarily due to the
direction of selected hysteresis. For the Cold option,
temperature has to fall below the threshold for the
output to assert High, and de-assert Low when the
temperature rises above the threshold plus the
hysteresis. For example, a 65°C threshold and 2°C
(typical) hysteresis, when temperature falls below 65°C
the output asserts High, and the de-asserts Low when
temperature rises above 67°C. For the Hot option, the
opposite is true. When temperature rises above 65°C,
the output asserts Low, and de-asserts High when the
temperature falls below 63°C. Figure 4-2 shows a
graphical description for the Hot and Cold options.
FIGURE 4-2: Output Hysteresis.
The Push-Pull output is ideal for a microcontroller
interface using an input/output pin or an interrupt input
pin. The open-drain option can be used with multiple
sensors in a wired-OR configuration or as a level
shifter.
I
SET
R
x
+
-
OUT/
OUT
Thermal
Diode
Hysteresis
Select Pin
Threshold
Select
Cold
Hot
T
SET
T
HYST
Temperature
V
Output
10°C Typical Hysteresis
2°C Typical
Hysteresis
Cold
Hot
T
SET
T
HYST
Temperature
V
Output
10°C Typical Hysteresis
2°C Typical
Hysteresis
Hot-Option (Active-Low)
Cold-Option (Active-High)