LM1042 datasheet(4/8 Pages) NSC

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Typical Performance Characteristics

Supply Voltage

Supply Current vs

Supply Voltage

Regulated Voltage vs

Supply Voltage

Probe Reference V vs

Pin 7 Voltage

Output Voltage vs

Pin 14 Voltage

Output Voltage vs

TLH8709 – 3

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

Pin 3

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

Pin 4

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

75V to a18V

protected against

50V 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 43V 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

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 12 and when shorted to ground

34 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

loop

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 01 mF and

not greater than 047 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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