LT3587
PIN FUNCTIONS
V
OUT1
(Pin 14):
Boost1 Output Pin. This pin is the drain
of an output disconnect PMOS transistor.
FB1 (Pin 15):
Boost1 Output Voltage Feedback Pin. Con-
nect a resistor R
FB1
from this pin to V
OUT1
(or CAP1)
such that:
R
FB1
= ((V
VOUT1
/1.22V) – 1) • 88.5k
There is an internal 88.5k resistor from the FB1 pin to
ground.
EN/SS1 (Pin 16):
Boost1/Inverter Shutdown and Soft-Start
Pin. Boost1 and Inverter are enabled when the voltage
on this pin is greater than 2.5V. They are disabled when
the voltage is below 0.2V. An internal 1μA current source
in conjunction with an external capacitor can be used to
ramp this pin and provide soft-start.
V
IN
(Pin 17):
Input Supply Pin. Must be locally bypassed
with an X5R or X7R type ceramic capacitor.
EN/SS3 (Pin 18):
Boost3 Shutdown and Soft-Start Pin.
Boost3 is enabled when the voltage on this pin is greater
than 2V. It is disabled when the voltage is below 0.2V. An
internal 1μA current source in conjunction with an exter-
nal capacitor can be used to ramp this pin and provide
soft-start.
I
FB3
(Pin 19):
Boost3 Output Current Programming Pin.
Connect a resistor R
IFB3
from this pin to ground such
that:
R
IFB3
= 200 • (0.8V/I
VOUT3
)
If Boost3 output is configured as a voltage regulator,
R
IFB3
can be optionally used to limit the maximum output
current to I
LIMIT
:
R
IFB3
= 200 • (0.8V/I
LIMIT
)
Note: Tie I
FB3
to GND when no current limit is desired.
V
FB3
(Pin 20):
Boost3 Output Voltage Feedback Pin. Con-
nect a resistor R
VFB3
from this pin to V
OUT3
(or CAP3)
such that:
R
VFB3
= ((V
VOUT3
/0.8V) – 1) • 56.3k
There is an internal 56.3k resistor from the V
FB3
pin to
ground. In the current regulator configuration, R
VFB3
can
be optionally used to limit the maximum output voltage
to V
CLAMP
, such that:
R
VFB3
= ((V
CLAMP
/0.8V) – 1) • 56.3k
Note: When no voltage clamp is desired in the current
regulator configuration, tie V
FB3
to GND.
Exposed Pad (Pin 21):
Ground Pin. Connect to PCB ground
plane. Ground plane connection through multiple vias under
the package is recommended for optimum electrical and
thermal performance.
3587fc
7
LINER [ LINEAR TECHNOLOGY ]
