ltm8042 Linear Technology Corporation, ltm8042 Datasheet - Page 13

• Manufacturer Part Number: ltm8042
• Description: Ltm8042/ltm8042-1 - ?module Boost Led Driver And Current Source
• Manufacturer: Linear Technology Corporation

TYPICAL PERFORMANCE CHARACTERISTICS
LTM8042-1
PIN FUNCTIONS
GND (Bank 1): Signal and Power Return. Tie these pads
to a local ground plane below the LTM8042/LTM8042-1
and the circuit components. In most applications, the
bulk of the heat flow out of the LTM8042/LTM8042-1 is
through these pads, so the printed circuit design has a
large impact on the thermal performance of the part. See
the PCB Layout and Thermal Considerations sections for
more details.
V
LTM8042/LTM8042-1. Connect to an external power
source between 3V and 30V. The LTM8042/LTM8042-1
can withstand transients of 40V.
BSTIN/BKLED
as Well as the Cathode Connection for the LED String in
Buck Mode. If the LTM8042/LTM8042-1 is used in boost
mode, these pins must be locally decoupled.
BSTOUT/BKIN (Bank 4): Output of the Boost Converter,
as Well as the Input for Buck Mode. If the LTM8042/
LTM8042-1 is used in buck mode, these pins must be
locally decoupled.
CC
(Bank 2): Internal Housekeeping Power for the
–
(Bank 3): Power Input for Boost Operation,
18
16
14
12
10
8
6
4
2
0
0
Junction Temperature Rise
vs Load, Buck-Boost Mode,
11.2V at 350mA LED String
50
100
LED CURRENT (mA)
150
12V
IN
5V
200
IN
250
300
80421 G77
350
LED
string. This can also be connected to the PWM dimming
MOSFET if used.
RUN (Pin F1): Module Enable. Tie to 1.5V or higher to
enable the LTM8042/LTM8042-1 or 0.4V or less to dis-
able device.
SYNC (Pin G1): Frequency Synchronization Pin. Tie an
external clock signal here. The RT resistor should be
chosen to program a switching frequency that is 20%
slower than SYNC pulse frequency. Tie the SYNC pin to
GND if this feature is not used.
RT (Pin H1): Timing Resistor Pin. Used to program the
switching frequency of the LTM8042/LTM8042-1 by con-
necting a resistor from this pin to GND. The Applications
Information section of the data sheet includes a table
to determine the resistance value based on the desired
switching frequency. Minimize capacitance at this pin.
SS (Pin J1): Soft-Start Pin. Place a soft-start capacitor
here. Leave the pin open if not used.
+
30
25
20
15
10
5
0
(Bank 5): Connect this to the anode of the LED
0
Junction Temperature Rise
vs Load, Buck-Boost Mode,
15.5V at 350mA LED String
50
T
A
= 25°C, unless otherwise noted.
100
LTM8042/LTM8042-1
LED CURRENT (mA)
12V
150
IN
5V
IN
200
250
300
80421 G78
350
13
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