LTM8042EVPBF datasheet(14/32 Pages) LINER

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LTM8042/LTM8042-1

80421fa

BLOCK DIAGRAM

80421 BD

CURRENT

MODE LED

CONTROLLER

0.1μF

4.7μH

0.1μF

BSTIN/BKLED–

RUN

PWM

SYNC

VCC

0.1μF

28.0k

20.0k

RSNS

0.10Ω (LTM8042)

0.27Ω (LTM8042-1)

GND

TGEN

CTL

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.

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