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HYST
SET0
HYST
SET1
SOH
OUT
Time
T =0
L
C
°
T =60
H
C°
10 C°
50 C°
5 C°
Measured
Temperature
Changeshysteresis
from10 toC 5 C
° °
ForcesOUTpinhigh
regardlessoftemperature
TMP303A
TMP303B
SBOS486B –JULY 2009–REVISED JANUARY 2011
www.ti.com
APPLICATION INFORMATION
The TMP303A temperature trip window resides within
The TMP303A and TMP303B are temperature
the range of 0°C to 60°C. The TMP303B temperature
switches used in battery-powered applications that
trip window resides within the range of 0°C to 55°C.
require accurate monitoring of a very specific
When either of these trip thresholds is crossed, the
temperature range of 0°C to +60°C (TMP303A) or
output (OUT) changes state from low to high. OUT
0°C to +55°C (TMP303B). This functionality is
does not return to its original low state until the
accomplished through the preset trip window and two
temperature crosses the hysteresis threshold and
hysteresis bits, HYST
SET0
and HYST
SET1
. The preset
returns within the range of the 0°C to 60°C (or 0°C to
trip window temperature thresholds are configured at
55°C) window.
the factory; for other trip points, contact a TI
representative. Table 1 summarizes the bit setting As an example, if the TMP303A is configured with a
versus hysteresis temperature window. 10°C hysteresis window (that is, HYST
SET0
=
HYST
SET1
= V
S
), the output does not return to its low
Table 1. Bit Setting vs Hysteresis Window state until the temperature either crosses (T
L
+
hysteresis) = 10°C or (T
H
– hysteresis) = 50°C. The
HYST
SET1
HYST
SET0
HYSTERESIS
Set Output High (SOH) pin is intended to add test
GND GND 1°C
functionality to verify the connectivity of the output
GND V
S
2°C
(OUT) pin to the system controller or other
temperature response system. The SOH pin is
V
S
GND 5°C
internally pulled down to ground with a 100kΩ
V
S
V
S
10°C
resistor. If the SOH pin is grounded or left floating, it
has no effect on the behavior of the TMP303A. If the
Configuring the TMP303A/B
SOH pin is pulled high, the TMP303A immediately
forces the output high, regardless of temperature. It is
The TMP303A/B contains an active high, push-pull
very important to note that this response occurs even
output stage and does not require a pull-up resistor to
if the temperature falls within the 0°C to 60°C
V
S
for proper operation. Figure 10 shows a block
temperature window. Figure 11 illustrates this design
diagram of the TMP303A/B.
in graphical form.
Figure 10. TMP303A/B Block Diagram
Power-supply bypassing is strongly recommended;
use a 0.1µF capacitor placed as close as possible to
the supply pin.
Figure 11. TMP303A Output Transfer Curves with
Hysteresis Change from 10°C to 5°C and SOH
Functionality
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