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L6376D

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18
Overtemperature protection (OVT) L6376
10/18
5 Overtemperature protection (OVT)
If the chip temperature exceeds Θlim (measured in a central position in the chip) the chip
deactivates itself.
The following actions are taken:
● all the output stages are switched off;
● the signal DIAG is activated (active low).
Normal operation is resumed as soon as (typically after some seconds) the chip
temperature monitored goes back below Θ
lim
-Θ
H
.
The different thresholds with hysteretic behavior assure that no intermittent conditions can
be generated.
6 Undervoltage protection (UV)
The supply voltage is expected to range from 9.5 V to 35 V, even if its reference value is
considered to be 24 V. In this range the device operates correctly. Below 9.5 V the overall
system has to be considered not reliable. Consequently the supply voltage is monitored
continuously and a signal, called UV, is internally generated and used.
The signal is “on” as long as the supply voltage does not reach the upper internal threshold
of the Vs comparator V
sth
. The UV signal disappears above V
sth
.
Once the UV signal has been removed, the supply voltage must decrease below the lower
threshold (i.e. V
sth
-V
shys
) before it is turned on again.
The hysteresis V
shys
is provided to prevent intermittent operation of the device at low supply
voltages that may have a superimposed ripple around the average value.
The UV signal switches off the outputs, but has no effect on the creation of the reference
voltages for the internal comparators, nor on the continuous operation of the charge-pump
circuits.
7 Diagnostic logic
The situations that are monitored and signalled with the DIAG output pin are:
● current limit (OVC) in action; there are 4 individual current limiting circuits, one per each
output; they limit the current that can be sunk from each output, to a typical value of
800 mA, equal for all of them;
● under voltage (UV);
● over temperature protection (OVT).
The diagnostic signal is transmitted via an open drain output (for ease of wired-or
connection of several such signals) and a low level represents the presence of at least one
of the monitored conditions, mentioned above.
L6376 Short circuit operation
11/18
8 Short circuit operation
In order to allow normal operation of the other inputs when one channel is in short cirtuit, an
innovative non dissipative over current protection (patent pending) is implemented in the
device.
In this way, the temperature of the device is kept enough low to prevent the intervention of
the thermal protection (in most of the cases) and so to avoid the shut down of the whole
device.
If a short circuit condition is present on one output, the current limiting circuit puts that
channel in linear mode — sourcing the ISC current (typically 800 mA) — for a time period
(t
ON
) defined by an external capacitor (C
DON
connected to the ON DELAY pin).
After that period, if the short circuit condition is still present the output is turned off for
another time period (t
OFF
) defined by a second external capacitor (C
DOFF
connected to the
OFF DELAY pin).
When also this period is expired:
● if the short circuit condition is still present the output stays on for the tON period and the
sequence starts again;
● if the short circuit condition is not present anymore the normal operation of the output is
resumed.
The t
ON
and t
OFF
periods are completely independent and can be set from 64 µs to 15 µs,
using external capacitors ranging from 50 pF to 15 nF (1.28 µs/pF).
If the OFF DELAY pin is tied to ground (i.e. the C
DOFF
capacitor is not used) the t
OFF
time
period is 64 times the t
ON
period.
The diagnostic output (DIAG) is active when the output is switched off, while it is not active
when the output is on (i.e. during the t
ON
period) even if in that period a short circuit
condition is present.
Figure 5. Short circuit operation waveforms
OUTPUT
CURRENT
t
ON
t
ON
t
OFF
t
OFF
Time
t<t
ON
DIAG
(active low)
Time
Short CircuitShort Circuit
I
sc
I
out
D94IN105
Programmable diagnostic delay L6376
12/18
Typical waveforms for short circuit operation are shown in Figure 5.
If both the ON DELAY and the OFF DELAY pins are grounded the non dissipative over
current protection is inhibited and the outputs in short circuit remain on until the thermal
shutdown switch OFF the whole device. In this case the short circuit condition is not
signalled by the DIAG pin (that continues to signal the under voltage and over temperature
conditions).
9 Programmable diagnostic delay
The current limiting circuits can be requested to perform even in absence of a real fault
condition, for a short period, if the load is of capacitive nature or if it is a filament lamp (that
exhibits a very low resistance during the initial heating phase).
To avoid the forwarding of misleading — i.e. short diagnostic pulses in coincidence with the
intervention of the current limiting circuits when operating on capacitive loads — the
activation of the diagnostic can be delayed with respect to the intervention of one of the
current limiting circuits.
This delay can be defined by an external capacitor (C
DON
) connected between the ON
DELAY pin and ground.
10 Reset input
An external reset input R (pin 18) is provided to simultaneously switch OFF all the outputs:
this signal (active low) is in effect an asynchronous reset that keeps the outputs low
independently from the input signals. For example, this reset input can be used by the CPU
to keep the outputs low after a fault condition (signaled by the DIAG pin).
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18

L6376D

Mfr. #:
Buy L6376D
Manufacturer:
STMicroelectronics
Description:
Power Switch ICs - Power Distribution 0.5A Intel Power Sw
Lifecycle:
New from this manufacturer.
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