Datasheet

LTM8042/LTM8042-1
14
80421fa
BLOCK DIAGRAM
80421 BD
CURRENT
MODE LED
CONTROLLER
0.1µF
4.7µH
0.1µF
BSTIN/BKLED
–
RUN
SS
PWM
SYNC
V
CC
1M
0.1µF
28.0k
20.0k
1%
R
SNS
0.10 (LTM8042)
0.27Ω (LTM8042-1)
2V
GND RT TGEN CTL
TG
LED
+
BSTOUT/BKIN
CURRENT SENSE+
CURRENT SENSE–
OPEN LED
PROTECTION
(1V THRESHOLD)
50k
PIN FUNCTIONS
TG (Pin J7): Top Gate Driver Output. In response to an
active high PWM signal, this pin will drive the gate of an
external series P-channel MOSFET device low. An internal
7V clamp protects the PFET gate. This pin can also be used
to disconnect the load when RUN is pulled low. Leave TG
unconnected if not used.
PWM (Pin K1): Pulse Width Modulation Input Pin. A low
signal turns off the LED string, disables the main switch
and pulls the TG pin high. Drive above 1.55V to deliver
current to the output. Tie the PWM pin to the RUN pin if
not used. There is an equivalent 50k resistor from PWM
pin to ground internally.
CTL (Pin L2): LED Current Adjustment Pin. Apply a voltage
between approximately 1V and 0V to modulate the LED
+
output current, or tie a resistor to GND to modulate the
LED
+
current. CTL is internally tied to a 2V precision refer-
ence via a 20k 1% resistor. Leave floating if unused.
TGEN (Pin L3): Top Gate (TG) Enable Input Pin. Tie to 1.5V
or higher to enable the P-channel MOSFET driver function.
Tie the TGEN pin to ground if the TG function is not used.
There is an internal 40k resistor from TGEN to GND.