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LM1042N View Datasheet(PDF) - National ->Texas Instruments

Part NameLM1042N National-Semiconductor
National ->Texas Instruments National-Semiconductor
DescriptionFluid Level Detector
LM1042N Datasheet PDF : 8 Pages
1 2 3 4 5 6 7 8
Typical Performance Characteristics
Supply Current vs
Supply Voltage
Regulated Voltage vs
Supply Voltage
Probe Reference V vs
Supply Voltage
Output Voltage vs
Pin 7 Voltage
Output Voltage vs
Pin 14 Voltage
Pin Function Description
Pin 1 Input amplifier for thermo-resistive probe with 5 nA
maximum leakage Clamped to ground at the start of
a probe 1 measurement
Pin 2 Device ground 0V
Pin 3
Pin 4
This pin is connected to the emitter of an external
PNP transistor to supply a 200 mA constant current
to the thermo-resistive probe An internal reference
maintains this pin at VSUPPLY b 2V
Base connection for the external PNP transistor
Pin 5 This pin is connected to the thermo-resistive probe
for short and open circuit probe detection
Pin 6 Supply pin a7 5V to a18V protected against
a50V transients
Pin 7 High Impedance input for second linear voltage
probe with an input range from 1V to 5V The gain
may be set externally using pin 10
Pin 8
Probe select and control input If this pin is taken to
a logic low level probe 1 is selected and the timing
cycle is initiated The selection logic is subsequently
latched low until the end of the measurement If kept
at a low level one shot or repeating probe 1 mea-
surements will be made depending upon pin 9 condi-
tions A high input level selects probe 2 except dur-
ing a probe 1 measurement period
Pin 9
The repeat oscillator timing capacitor is connected
from this pin to ground A 2 mA current charges up
the capacitor towards 4 3V when the probe 1 mea-
surement cycle is restarted If this pin is grounded
the repeat oscillator is disabled and only one probe
1 measurement will be made when pin 8 goes low
TL H 8709 – 3
Pin 10 A resistor may be connected to ground to vary the
gain of the probe 2 input amplifier Nominal gain
when open circuit is 1 2 and when shorted to ground
3 4 DC conditions may be adjusted by means of a
resistor divider network to VREG and ground
Pin 11 Regulated voltage output Requires to be connected
to pin 15 to complete the supply regulator control
Pin 12 The capacitor connected from this pin to ground
sets the timing cycle for probe 1 measurements
Pin 13 The resistor connected between this pin and ground
defines the charging current at pin 12 Typically 12k
the value should be within the range 3k to 15k
Pin 14 A low leakage capacitor typical value 0 1 mF and
not greater than 0 47 mF should be connected from
this pin to the regulated supply at pin 11 to act as a
memory capacitor for the probe 1 measurement
The internal leakage at this pin is 2 nA max for a
long memory retention time
Pin 15 Feedback input for the internal supply regulator nor-
mally connected to VREG at pin 11 A resistor may
be connected in series to adjust the regulated output
voltage by an amount corresponding to the 1 mA
current into pin 15
Pin 16 Linear voltage output for probe 1 and probe 2 capa-
ble of driving up to g10 mA May be connected with
a 600X meter to VREG
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