LM57CISDX-5/NOPB National Semiconductor, LM57CISDX-5/NOPB Datasheet - Page 14

• Manufacturer Part Number: LM57CISDX-5/NOPB
• Description: IC PROG TEMP SWITCH SENSOR 8-LLP
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM57CISDX-5/NOPB

• Sensing Temperature: -50°C ~ 150°C
• Output Type: Open Drain, Push-Pull
• Voltage - Supply: 2.4 V ~ 5.5 V
• Accuracy: ±2.3°C
• Package / Case: 8-WFDFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LM57CISD-5X; LM57CISD-5X; LM57CISD-5X/NOPB; LM57CISDX-5

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V
LM57 will not be correct. Printed-circuit coatings are often
used to ensure that moisture cannot corrode the leads or cir-
cuit traces.
The LM57's junction temperature is the actual temperature
being measured. The thermal resistance junction-to-ambient
(θ
rise of a device junction temperature due to its power dissi-
pation. The equation used to calculate the rise in the LM57's
die temperature is
where T
rent, I
For example, in an application where T
V, I
total temperature rise would be [152°C/W*5.5V*28μA] =
0.023°C. To minimize self-heating, the load current on Vtemp
should be minimized.
7.0 Rset TABLE
The LM57 uses the voltage at the two Rsense pins to set the
trip point for the temperature switch. It is possible to drive the
TEMP
Device Number
JA
DD
) is the parameter (from Figure 4) used to calculate the
L
= 28 μA, J5 gain, V
output to ground or V
is the load current on Vtemp.
LM57
A
is the ambient temperature, I
FIGURE 4. LM57 Thermal Resistance
Resistance (θ
152° C/W
TEMP
Thermal
DD
= 2368 mV, and I
, the V
JA
)
Q
TEMP
A
is the quiescent cur-
= 30 °C, V
NS Package
output from the
Number
SDA08B
L
= 0 μA, the
DD
= 5.5
14
two Rsense pins with a voltage equal to the value generated
by the resistor and the internal current-source and have the
same switch point. Thus one can use an external DAC to drive
each Rsense pin, allowing for the temperature trip point to be
set dynamically by the system processor. The table shows the
Rset value and its corresponding generated Rsense pin volt-
age (the “Center Value").
Rset (Ω)
Rset Values (kΩ) vs Rsense Voltage (mV)
46.4k
22.6k
0.01k
976k
825k
698k
590k
499k
412k
340k
280k
226k
178k
140k
105k
75k
Rsense Voltage (mV)
Center Value
1875
1585
1341
1134
959
792
653
538
434
342
269
202
146
87
43
0