Datasheet

LT8410/LT8410-1
7
84101fb
PIN FUNCTIONS
SHDN (Pin 1): Shutdown Pin. This pin is used to enable/
disable the chip. Drive below 0.3V to disable the chip. Drive
above 1.45V to activate the chip. Do not float this pin.
V
CC
(Pin 2): Input Supply Pin. Must be locally bypassed
to GND. See the Typical Applications section.
GND (Pin 3): Ground. Tie directly to local ground plane.
SW (Pin 4): Switch Pin. This is the collector of the inter-
nal NPN power switch. Minimize the metal trace area
connected to this pin to minimize EMI.
V
OUT
(Pin 5): Drain of Output Disconnect PMOS. Place
a bypass capacitor from this pin to GND.
CAP (Pin 6): Cathode of the Internal Schottky Diode. Place
a bypass capacitor from this pin to GND.
V
REF
(Pin 7): Reference Pin. Soft-start can be achieved
by placing a capacitor from this pin to GND. This cap
will be discharged for 70µs (typical) at the beginning
of start-up and then be charged to 1.235V with a 10μA
current source.
FBP (Pin 8): Positive Feedback Pin. This pin is the error
amplifier’s positive input terminal. To achieve the desired
output voltage, choose the FBP pin voltage (V
FBP
) accord-
ing to the following formula:
V
FBP
=
V
OUT
31.85
For protection purposes, the output voltage can not exceed
40V even if V
FBP
is driven higher than V
REF
.
Exposed Pad (Pin 9): Pin 9 is floating but must be ground-
ed for proper shielding.
BLOCK DIAGRAM
2
7
8
9
–
+
+
DISCHARGE
CONTROL
ENABLE
CHIP
1.235V
V
REF
V
CC
FBP
FB
VC
GND
EXPOSED PAD
(GND)
400k
CAP
MAX
10µA
SWSHDN
12.4M
V
OUT
SWITCH
CONTROL
–
+
TIMING AND PEAK
CURRENT CONTROL
–
+
1
1.235V
3
5 6
4
OUTPUT DISCONNECT
CONTROL
1.235V
–
+