LM26LV Datasheet, PDF (19/33 Pages) National Semiconductor (TI) – 1.6 V, LLP-6 Factory Preset Temperature Switch and Temperature Sensor

LM26LV
www.ti.com
SNIS144F – JULY 2007 – REVISED FEBRUARY 2013
NOISE IMMUNITY
The LM26LV/LM26LV-Q1 is virtually immune from false triggers on the OVERTEMP and OVERTEMP digital
outputs due to noise on the power supply. Test have been conducted showing that, with the die temperature
within 0.5°C of the temperature trip point, and the severe test of a 3 Vpp square wave "noise" signal injected on
the V_DD line, over the V_DD range of 2V to 5V, there were no false triggers.
TRIP TEST Digital Input
The TRIP TEST pin simply provides a means to test the OVERTEMP and OVERTEMP digital outputs
electronically by causing them to assert, at any operating temperature, as a result of forcing the TRIP TEST pin
high.
When the TRIP TEST pin is pulled high the V_TEMP pin will be at the V_TRIP voltage.
If not used, the TRIP TEST pin may either be left open or grounded.
V_TEMP Analog Temperature Sensor Output
The V_TEMP push-pull output provides the ability to sink and source significant current. This is beneficial when, for
example, driving dynamic loads like an input stage on an analog-to-digital converter (ADC). In these applications
the source current is required to quickly charge the input capacitor of the ADC. See the Applications Circuits
section for more discussion of this topic. The LM26LV/LM26LV-Q1 is ideal for this and other applications which
require strong source or sink current.
NOISE CONSIDERATIONS
The LM26LV/LM26LV-Q1's supply-noise rejection (the ratio of the AC signal on V_TEMP to the AC signal on V_DD)
was measured during bench tests. It's typical attenuation is shown in the Typical Performance Characteristics
section. A load capacitor on the output can help to filter noise.
For operation in very noisy environments, some bypass capacitance should be present on the supply within
approximately 2 inches of the LM26LV/LM26LV-Q1.
CAPACITIVE LOADS
The V_TEMP Output handles capacitive loading well. In an extremely noisy environment, or when driving a switched
sampling input on an ADC, it may be necessary to add some filtering to minimize noise coupling. Without any
precautions, the V_TEMP can drive a capacitive load less than or equal to 1100 pF as shown in Figure 21. For
capacitive loads greater than 1100 pF, a series resistor is required on the output, as shown in Figure 22, to
maintain stable conditions.
OPTIONAL
BYPASS
CAPACITANCE
V_DD
V_TEMP
LM26LV
GND
C_LOAD d 1100 pF
Figure 21. LM26LV/LM26LV-Q1 No Decoupling Required for Capacitive Loads Less than 1100pF.
OPTIONAL
BYPASS
CAPACITANCE
V_DD
LM26LV ^{VTEMP RS}
GND
C_LOAD >
1100 pF
Figure 22. LM26LV/LM26LV-Q1 with series resistor for capacitive loading greater than 1100pF
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