LT1946 LINER [Linear Technology], LT1946 Datasheet - Page 4

• Manufacturer Part Number: LT1946
• Description: 1.2MHz Boost DC/DC Converter with 1.5A Switch and Soft-Start
• Manufacturer: LINER [Linear Technology]

BLOCK DIAGRA
LT1946
V
pensation network to this pin, or use the internal compen-
sation network by shorting the V
FB (Pin 2): Feedback Pin. Reference voltage is 1.250V.
Connect resistive divider tap here. Minimize trace area at
FB. Set V
SHDN (Pin 3): Shutdown Pin. Tie to 2.4V or more to enable
device. Ground to shut down. Do not float this pin.
GND (Pin 4): Ground. Tie directly to local ground plane.
SW (Pin 5): Switch Pin. This is the collector of the internal
NPN power switch. Minimize the metal trace area con-
nected to this pin to minimize EMI.
PI FU CTIO S
4
C
(Pin 1): Error Amplifier Output Pin. Tie external com-
U
SHUTDOWN
OUT
U
V
OUT
according to V
R1 (EXTERNAL)
R2 (EXTERNAL)
SHDN
FB
V
6
3
IN
U
REFERENCE
W
1.250V
OUT
= 1.250(1 + R1/R2).
C
SS
FB
8
2
pin to the COMP pin.
0.5V
+
–
+
–
4 A
A1
A3
Figure 2. Block Diagram
V
3
1
C
OSCILLATOR
GENERATOR
COMP
1.2MHz
RAMP
7
V
COMP (Pin 7): Internal Compensation Pin. Provides an
internal compensation network. Tie directly to the V
for internal compensation. Tie to GND if not used.
SS (Pin 8): Soft-Start Pin. Place a soft-start capacitor
here. Upon start-up, 4 A of current charges the capacitor
to 1.5V. Use a larger capacitor for slower start-up. Leave
floating if not in use.
120k
IN
90pF
(Pin 6): Input Supply Pin. Must be locally bypassed.
–
+
A2
COMPARATOR
R
S
Q
DRIVER
+
–
1946 BD
GND
SW
5
4
Q1
0.01
sn1946 1946fs
C
pin