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L4620 View Datasheet(PDF) - STMicroelectronics

Part Name
STMicroelectronics ST-Microelectronics
L4620 Datasheet PDF : 9 Pages
1 2 3 4 5 6 7 8 9
PIN FUNCTION (Block Diagram)
1 Oscillator
A capacitor Cosc connected to ground and a resistor Rosc connected to pin 5 (supply
voltage) set the frequency of the internal oscillator. The period is given by: Tosc = 0.693
(Rosc + 5000) Cosc
2 Sensor Output A squarewave is available at this pin to drive the external sensor. The output
frequency is 1/32 of the internal oscillator fosc, i.e. 50Hz using the values of
Rosc = 180kand Cosc = 4.7nF for the external components.
3 Sensor Input Connection for liquid level sensing. During the zero level of the squarewave signal at
pin 2, the internal sensing circuit is disabled. During the high level of the wave shape
the input is compared with a threshold which depends on the output sensor volta
VSENSH = 0.4V2 (typ). If the input voltage becomes higher than the above VSENSH, the
Vsens value is reduced to VSENSL = 0.22V2 (typ), providing an hysteresis available with
both the programmable polarities.
This pin must be connected to ground.
5 Supply Voltage Supply voltage input. A 4.5V (typical) zener is present at the input. The external
resistor limits the current through the zener for high supply voltages. Moreover when
the voltage at this pin is down 2.5V (typical) the internal reset circuit is activated
6 Alarm Driver An internal open collector stage is available at this pin to drive the external alarm
indicator by a rectangular waveshape. The output period depends on the external
component Rosc and Cosc. Using the recommended values of block diagram th
7 Alarm Delay
This program pin selects the alarm delay to activate the output stage after a low liquid
level indication of the sensor. The delay depends on the internal oscillator frequency.
Refer to application circuit, if this pin is kept low the typical delay is 10.
8 Sensor Polarity Through this pin it is possible to program both the sensor polarity with respect to the
Select Output internal threshold and the duty-cycle of the output waveform which drives the alarm.
When this pin is kept low the output rectangular wave duty cycle is 1:64
(T = 320ms, t = 5ms in fig. 2) and the output is activated, after the delay time, if the
voltage at pin 3 is higher than VSENS. When the voltage at this pin is high the output
duty cycle is 50% (t = 160ms) and the output goes on, after the delay

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