LM94023BITME NSC [National Semiconductor], LM94023BITME Datasheet - Page 11

• Manufacturer Part Number: LM94023BITME
• Description: 1.5V, micro SMD, Dual-Gain Analog Temperature Sensor with Class AB Output
• Manufacturer: NSC [National Semiconductor]

2.0 Mounting and Thermal
Conductivity
The LM94023 can be applied easily in the same way as other
integrated-circuit temperature sensors. It can be glued or ce-
mented to a surface.
To ensure good thermal conductivity, the backside of the
LM94023 die is directly attached to the GND pin (Pin 2). The
temperatures of the lands and traces to the other leads of the
LM94023 will also affect the temperature reading.
Alternatively, the LM94023 can be mounted inside a sealed-
end metal tube, and can then be dipped into a bath or screwed
into a threaded hole in a tank. As with any IC, the LM94023
and accompanying wiring and circuits must be kept insulated
and dry, to avoid leakage and corrosion. This is especially true
if the circuit may operate at cold temperatures where con-
densation can occur. If moisture creates a short circuit from
the output to ground or V
not be correct. Printed-circuit coatings are often used to en-
sure that moisture cannot corrode the leads or circuit traces.
The thermal resistance junction to ambient (θ
rameter used to calculate the rise of a device junction tem-
perature due to its power dissipation. The equation used to
calculate the rise in the LM94023's die temperature is
where T
rent, I
voltage. For example, in an application where T
V
and I
showing a self-heating error of only 0.021°C. Since the
LM94023's junction temperature is the actual temperature
being measured, care should be taken to minimize the load
current that the LM94023 is required to drive. Figure 1 shows
the thermal resistance of the LM94023.
3.0 Output and Noise
Considerations
A push-pull output gives the LM94023 the ability to sink and
source significant current. This is beneficial when, for exam-
ple, 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 discus-
sion of this topic. The LM94023 is ideal for this and other
applications which require strong source or sink current.
The LM94023's supply-noise gain (the ratio of the AC signal
on V
tests. It's typical attenuation is shown in the Typical Perfor-
mance Characteristics section. A load capacitor on the output
can help to filter noise.
DD
LM94023BITME,
Device Number
LM94023BITMX
OUT
= 5 V, I
L
L
= 2 μA, the junction temperature would be 30.021 °C,
is the load current on the output, and V
A
to the AC signal on V
FIGURE 1. LM94023 Thermal Resistance
is the ambient temperature, I
DD
= 9 μA, Gain Select = 11, V
NS Package
TMD04AAA
DD
Number
, the output from the LM94023 will
DD
) was measured during bench
Q
is the quiescent cur-
Resistance (θ
OUT
122.6 °C/W
Thermal
O
JA
is the output
= 2.231 mV,
) is the pa-
A
= 30 °C,
JA
)
11
For operation in very noisy environments, some bypass ca-
pacitance should be present on the supply within approxi-
mately 2 inches of the LM94023.
4.0 Capacitive Loads
The LM94023 handles capacitive loading well. In an extreme-
ly 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
LM94023 can drive a capacitive load less than or equal to
1100 pF as shown in Figure 2. For capacitive loads greater
than 1100 pF, a series resistor may be required on the output,
as shown in Figure 3.
5.0 Output Voltage Shift
The LM94023 is very linear over temperature and supply volt-
age range. Due to the intrinsic behavior of an NMOS/PMOS
rail-to-rail buffer, a slight shift in the output can occur when
the supply voltage is ramped over the operating range of the
device. The location of the shift is determined by the relative
levels of V
V
This slight shift (a few millivolts) takes place over a wide
change (approximately 200 mV) in V
shift takes place over a wide temperature change of 5°C to
20°C, V
in the Electrical Characteristics table already include this pos-
sible shift.
FIGURE 3. LM94023 with series resistor for capacitive
DD
- V
FIGURE 2. LM94023 No Decoupling Required for
OUT
OUT
Capacitive Loads Less than 1100 pF.
= 1.0V.
DD
is always monotonic. The accuracy specifications
100 nF to 999 nF
1.1 nF to 99 nF
Loading greater than 1100 pF.
and V
C
1 μF
LOAD
OUT
. The shift typically occurs when
Minimum R
1.5 kΩ
800 Ω
3 kΩ
DD
or V
S
OUT
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