SGS Thomson Microelectronics L4620 Datasheet
DRIVESDIRECTLY300 mAALARMLOAD
.
PROGRAMMABLEINPUTPOLARITYTO
.
ACTIVATETHEOUTPUT STAGE
PROGRAMMABLEDELAYTIME
.
PROGRAMMABLEOUTPUTDUTY CYCLE
.
OUTPUTSHORTCIRCUITPROTECTION
.
OVERVOLTAGEANDTHERMAL
.
PROTECTION
L4620
LIQUIDLEVEL ALARM
Minidip
DESCRIPTION
The L4620is anintegratedcircuit,designedforthe
liquid level control in automotiveapplications. The
liquid level is indicated by an attenuationbetween
transmittedand receivedsignalacrossa sensortip
in thelquid. If the attenuationexceedesan internal
threshold- sensortipoutsidetheliquidorliquidtemperaturehigherthana determinedvalue- asquarewave alarm output indicates an unsufficient liquid
condition.Iftheliquidlevelisrestoredbeforetheend
of a delaytime the alarmis notactivated.
Throughtwopinsitis possibletoprogram:thedelay
BLOCK DIAGRAM
ORDERING NUMBER : L4620
time to activate thealarm, the duty cycleof the
output squarewave,the polarity ofthe input thresholdof thesensorfor alarmactivation.
TheabovefeaturesmaketheL4620particularlyversatilefor many applicationsand givethe possibility
tousevarioussensor types.
Internal circuits prevent spurious indications from
the liquid sensor and a latch keeps the alarmactivateduntilthesupplyvoltageisswitchedoff.Thedeviceincludesthermalshutdownprotections.
December 1999
1/9
L4620
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter Value Unit
I
V
I
out
P
T
j,Tstg
PI N CONNE CTION (top view)
Supply Current (VS>VZ) 200 mA
S
Sensor Input Voltage (V2High) 7 V
3
Output Current 500 mA
Power Dissipation at T
tot
amb
=70°C
0.8 W
Junction and Storage Temperature Range – 55 to 150
°C
THERMAL DATA
Symbol Parameter Value Unit
Thermal Resistance Junction-ambient Max 100 °
2/9
R
th j-amb
C/W
PIN FUNCTION (BlockDiagram)
L4620
N
°
1 Oscillator A capacitor C
Name Function
connected to ground and a resistor R
osc
voltage) set the frequency of the internal oscillator. The period is given by: T
+ 5000) C
(R
osc
osc
connected to pin 5 (supply
osc
osc
= 0.693
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
= 180kΩand C
R
osc
= 4.7nF for the external components.
osc
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
= 0.4V2(typ). If the input voltage becomes higher than the above V
V
SENSH
value is reduced to V
V
sens
= 0.22V2(typ), providing an hysteresis available with
SENSL
SENSH
, the
both the programmable polarities.
4 GND 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
Output
7 Alarm Delay
Select
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 R
osc
and C
. Using the recommended values of block diagram th
osc
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
Select Output
Duty-cycle
Select
Through this pin it is possible to program both the sensor polarity with respect to the
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 V
. When the voltage at this pin is high the output
SENS
duty cycle is 50% (t = 160ms) and the output goes on, after the delay
3/9
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