lt3479efe-trpbf Linear Technology Corporation, lt3479efe-trpbf Datasheet - Page 4

• Manufacturer Part Number: lt3479efe-trpbf
• Description: 3a, Full Featured Dc/dc Converter With Soft-start And Inrush Current Protection
• Manufacturer: Linear Technology Corporation

PI FU CTIO S
LT3479
SW (Pins 1, 2/Pins 1, 2): Switch Pins. Collector of the
internal NPN power switch. Connect the inductor and
diode here and minimize the metal trace area connected to
this pin to minimize electromagnetic interference.
L (Pin 3/Pin 3): Inductor Pin. Connect the inductor to this
pin.
V
passed. Powers the switch and the inductor. In case only
one supply voltage is available, tie V
V
Powers the internal control circuitry.
R
ing frequency. Do not leave this pin open. See Table 4 for
R
SHDN (Pin 7/Pin 7): Shutdown. Tie to 1.5V or greater to
enable the device. Tie below 0.3V to turn off the device.
V
set to 1.235V. Connect this pin to FBP if generating a posi-
tive output, or to an external resistor divider if generating
a negative voltage. This pin can provide up to 100µA of cur-
rent and can be locally bypassed with a 100pF capacitor.
4
TYPICAL PERFOR A CE CHARACTERISTICS
S
IN
REF
T
T
15
20
10
U
(Pin 6/Pin 6): Timing Resistor Pin. Adjusts the switch-
5
values and switching frequencies.
0
(Pin 4/Pin 4): Inductor Supply. Must be locally by-
(Pin 5/Pin 5): Input Supply. Must be locally bypassed.
–50
Soft-Start Pin Current
(Pin 8/Pin 9): Bandgap Voltage Reference. Internally
–25
U
0
TEMPERATURE (°C)
25
50
U
75
(DFN/TSSOP)
100
W
125
3479 G07
150
U
IN
and V
0.4
2.0
1.6
1.2
0.8
0
S
–50
Oscillator Frequency
together.
–25
0
TEMPERATURE (°C)
25
R
R
R
T
T
T
= 10kΩ
= 15kΩ
= 20kΩ
50
FBP (Pin 9/Pin 10): The Noninverting Input to the Error
Amplifier. Connect resistive divider tap here for negative
output voltage.
FBN (Pin 10/Pin 11): The Inverting Input to the Error
Amplifier. Connect resistive divider tap here for positive
output voltage.
V
Connect a series RC from this pin to GND. Typical values
are 10kΩ and 2.2nF.
SS (Pin 12/Pin 13): Soft-Start. Place a soft-start capacitor
here. Leave floating if not in use.
GND (Pins 13, 14/Pins 8, 14, 15, 16): Ground. Tie directly
to local ground plane.
Exposed Pad (Pin 15/Pin 17): Power Ground. Must be
connected to electrical PCB ground.
C
(Pin 11/Pin 12): Compensation Pin for Error Amplifier.
75
100
125
3479 G08
150
5
4
3
2
1
0
–50
Feedback Amplifier Offset Voltage
–25
TEMPERATURE (°C)
0
25
50
V
V
C
C
= 0.5V
75
= 1V
3479 G09
3479fa
100