STLC1 STMICROELECTRONICS [STMicroelectronics], STLC1 Datasheet - Page 7

• Manufacturer Part Number: STLC1
• Description: LED LAMPS CLUSTER DRIVER
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

only when the OUT voltage is about 95% of its
final value. Such a start-up phase takes place
when only one input is enabled.
LOW SIDE DRIVER:
The purpose of the low side drivers is to connect
the LED cluster to ground, creating a path for the
current. Using external resistors, current flowing
into the LED cluster is set according to the
following formula:
I
where (see typical application schematic):
R
R
R
V
V
LSD over-current protection and under-current
diagnostic (see LAMP OUTAGE DETECTION
section) is performed by sensing the voltage on
resistors, when the corresponding LSD are
enabled.
If the voltage on
over-current protection acts by reducing the LSD
average current by switching ON and OFF the
LSD itself.
LAMP OUTAGE DETECTION
Resistors are used to sense the LED array
current. In case one or more LEDs fail (open
circuit) the current on the corresponding resistor
will drop due to the increased LED array
resistance. As soon as the voltage drop on
lower than V
ARRAY
OUT
ARRAY
L
T
(on)
= R
= R
= Static drain to source LSD on resistance
= Output Voltage
LT
TT
, R
= Expected LED array voltage drop.
, R
=
V
--------------------------------------------- -
LS
TS
R
LOUT
OUT
T
, or R
, or R
+
R
, a LED lamp fault condition is
–
L
LR
TR
V
+
ARRAY
R
exceeds V
on
H-SHORT
, the
is
detected and the LMP-OUT pin becomes active
(low).
AND-ed with each input, that is a fault condition
can be detected only when the LED arrays are
enabled.
DIMMING
The dimming of the LED lamps can be obtained by
using the internal PULSE WIDTH controller (it
drives the LSD TAIL and STOP gates). The duty
cycle of this internal oscillator (whose frequency is
380Hz typical) can be set, forcing the voltage of
the CNTL pin to be a fraction of V
simple resistor divider (as shown in the typical
application scheme).
In this case the duty cycle percentage can be
calculated
formula:
The TS-PWM pin voltage, according to the
TABLE1 determines which LSD is PULSE WIDTH
CONTROLLER driven. Internal dimming can only
be performed on the TAIL and STOP arrays. The
TURN array can be externally dimmed (as well as
TAIL and STOP) by driving the corresponding
input witha a square pulse signal whose maximum
frequency must be 200Hz.
DC%





The
---------------------------- 100 Elsewhere
R
C1
3.8 if
R
with
+
C1
LAMP-OUTAGE
R
----------------------------
R
C2
C1
the
R
+
C1
R
following
C2
------------- -
V
0.2
REF
functionality
REF
approximated
, by using a





STLC1
7/16
is