LT3514
8
3514fa
For more information www.linear.com/LT3514
PIN FUNCTIONS
NC (Pins 1, 2, 14, 22/Pins 2, 10): No Connection. These
pins have no connection to internal circuitry. They can be
grounded or left floating.
DA (Pins 3, 6, 8/Pins 3, 7, 9): Return the Schottky catch
diode anode to the diode anode (DA) pin. An internal com
-
parator senses the diode current and prevents switching
when
the
diode current is higher than the DA pin current
limit.
SW (Pins 4, 5, 7/Pins 4, 5, 6, 8): The SW pins are the
output of the internal power switches. Connect each SW
pin to an inductor and Schottky catch diode cathode.
V
IN
(Pins 9, 11, 26, 28/Pins 1, 11, 12): The V
IN
pins sup-
ply current to the LT3514’s internal regulator and to the
internal power switches. The
V
IN
pins should be locally
bypassed with a capacitor to ground, preferably to pins
27 and 10. They must be tied to the same input source.
GND (Pins 10, 18, 27, Exposed Pad Pin 29/Pin 22,
Exposed Pad Pin 25): Tie the GND pins to a local ground
plane below the LT3514 and the cir
cuit components. The
exposed pad must be soldered to the PCB and electrically
connected to ground. Use a large ground plane and thermal
vias to optimize thermal performance.
RUN/SS (Pins 12, 13, 15/Pins 13, 14, 15): The RUN/SS
pins are used to soft start each channel and to allow
each channel to track other outputs. Output tracking is
implemented by connecting a resistor divider to this pin
from the tracked output. For soft start, tie a capacitor from
this pin to ground. An internal 1.3µA soft-start current
charges the capacitor to create a voltage ramp at the pin.
Each channel can be individually shut down by pulling
RUN/SS below 0.1V.
EN/UVLO (Pin 16/Pin 16):
The EN/UVLO pin is used to
start up the internal regulator to power the reference and
oscillator. It also starts up the internal boost regulator. Pull
the EN/UVLO pin below 1.44V to shut down the LT3514.
The LT3514 will draw less than 10µA of current from the
V
IN
pin when EN/UVLO is less than 1.44V. Pull EN/UVLO
pin below 0.7V to put the LT3514 in a state where the part
draws 0µA from the V
IN
pin. The threshold can function
as an accurate undervoltage lockout (UVLO), preventing
the regulator from operating until the input voltage has
reached the programmed level. Do not drive the EN/UVLO
pin more than 5V above V
IN
.
(QFN/TSSOP)
Operating Waveforms,
Discontinuous Mode
Operating Waveforms,
Continuous Mode
500ns/DIV
3514 G29
SW1
10V/DIV
SW3
10V/DIV
SW4
10V/DIV
I
OUT1,3,4
= 40mA
V
OUT1,3,4
= 5V
500ns/DIV
3514 G30
SW1
10V/DIV
SW3
10V/DIV
SW4
10V/DIV
I
OUT1,3,4
= 0.5A
V
OUT1,3,4
= 5V
TYPICAL PERFORMANCE CHARACTERISTICS
T
A
= 25°C, unless otherwise noted.
