lt3471edd-trpbf Linear Technology Corporation, lt3471edd-trpbf Datasheet - Page 4

• Manufacturer Part Number: lt3471edd-trpbf
• Description: Dual 1.3a, 1.2mhz Boost/inverter In 3mm ? 3mm Dfn
• Manufacturer: Linear Technology Corporation

BLOCK DIAGRA
LT3471
FB1N (Pin 1): Negative Feedback Pin for Switcher 1.
Connect resistive divider tap here. Minimize trace area at
FB1N. Set V
for inverting topologies.
FB1P (Pin 2): Positive Feedback Pin for Switcher 1. Con-
nect either to V
connect to a resistive divider tap for inverting topologies.
V
of current. Do not pull this pin high. Must be locally
bypassed with no less than 0.01 µ F and no more than 1 µ F .
A 0.1µF ceramic capacitor is recommended. Use this pin
as the positive feedback reference or connect a resistor
divider here for a smaller reference voltage.
FB2P (Pin 4): Same as FB1P but for Switcher 2.
FB2N (Pin 5): Same as FB1N but for Switcher 2.
SW2 (Pin 6): Switch Pin for Switcher 2 (Collector of
internal NPN power switch). Connect inductor/diode here
PI FU CTIO S
4
REF
U
(Pin 3): 1.00V Reference Pin. Can supply up to 1mA
U
OUT
REF
= V
FB1P
or a divided down version of V
U
2
1
8
9
4
5
7
(1 + R1/R2), or connect to ground
FB1P
FB1N
V
SHDN/SS1
FB2P
FB2N
SHDN/SS2
IN
W
+
–
+
–
REFERENCE
A1
A3
SHIFTER
SHIFTER
1.00V
LEVEL
LEVEL
V
REF
R
R
3
C
C
C
C
C
C
Figure 1. Block Diagram
REF
GENERATOR
GENERATOR
OSCILLATOR
, or
1.2MHz
RAMP
RAMP
Σ
Σ
–
+
–
+
A4
and minimize the metal trace area connected to this pin to
minimize EMI.
SHDN/SS2 (Pin 7): Shutdown and Soft-Start Pin. Tie to
1.8V or more to enable device. Ground to shut down. Soft-
start function is provided when the voltage at this pin is
ramped slowly to 1.8V with an external RC circuit.
V
SHDN/SS1 (Pin 9): Same as SHDN/SS2 but for Switcher 1.
Note: taking either SHDN/SS pin high will enable the part.
Each switcher is individually enabled with its respective
SHDN/SS pin.
SW1 (Pin 10): Same as SW2 but for Switcher 1.
Exposed Pad (Pin 11): Ground. Connect directly to local
ground plane. This ground plane also serves as a heat sink
for optimal thermal performance.
A2
IN
(Pin 8): Input Supply. Must be locally bypassed.
R
R
S
S
3471 F01
Q
Q
DRIVER
DRIVER
+
–
+
–
GND
10
11
6
Q1
Q2
0.01Ω
0.01Ω
SW1
GND
SW2
3471fa