lt8415 Linear Technology Corporation, lt8415 Datasheet - Page 6

• Manufacturer Part Number: lt8415
• Description: Ultralow Power Boost Converter With Dual Half-bridge Switches
• Manufacturer: Linear Technology Corporation

PIN FUNCTIONS
LT8415
SHDN (Pin 1): Shutdown Pin. This pin is used to enable/dis-
able the chip. Drive below 0.3V to disable the chip. Drive
above 1.4V to activate the chip. Do not fl oat this pin.
V
to GND. See typical applications section.
GND (Pin 3 and Pin 13): Ground. Tie directly to local
ground plane. Pin 13 is fl oating but must be grounded
for proper shielding.
SW (Pin 4): Switch Pin. This is the collector of the internal
NPN power switch. Minimize the metal trace area connected
to this pin to minimize EMI.
IN1 (Pin 5): First Half-Bridge Control Input. Do not fl oat
this pin.
IN2 (Pin 6): Second Half-Bridge Control Input. Do not
fl oat this pin.
OUT2 (Pin 7): Second Half-Bridge Output. This pin is
controlled in phase by the voltage on IN2. The output level
is either the voltage on V
OUT1 (Pin 8): First Half-Bridge Output. This pin is controlled
in phase by the voltage on IN1. The output level is either
the voltage on V
BLOCK DIAGRAM
6
CC
(Pin 2): Input Supply Pin. Must be locally bypassed
V
R
R
FBP
REF
1
2
OUT
12
11
V
2
CC
or GND.
MAX
10μA
OUT
DISCHARGE
CONTROL
or GND.
+
–
1.235V
1.235V
ENABLE
CHIP
FB
–
+
+
+
–
1.235V
SHDN
VC
1
CURRENT CONTROL
TIMING AND PEAK
V
bypass capacitor from this pin to GND.
CAP (Pin 10): This is the Cathode of the Internal Schottky
Diode. Place a bypass capacitor from this pin to GND.
V
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 12): Positive Feedback Pin. This pin is the error
amplifi er’s positive input terminal. To achieve the desired
output voltage, choose the FBP pin voltage (V
ing to the following formula:
When resistor divider from the V
voltage, choose the resistor divider ratio according to the
following formula:
For protection purposes, the output voltage can not exceed
40V even if V
GND
12.4M
13
400K
OUT
REF
V
R1/R2 = (39.33 – V
FBP
(Pin 11): Reference Pin. Soft start can be achieved
(Pin 9): Drain of Output Disconnect PMOS. Place a
V
OUT
9
= V
OUTPUT DISCONNECT
OUT
CONTROL
FBP
/31.85
CONTROL
SWITCH
is driven higher than V
CAP
10
+
–
OUT
GND IN1
SW
4
3
)/V
5
OUT
BOTTOM GATE
IN2
REF
6
TOP GATE
CONTROL
CONTROL
BOTTOM GATE
is used to set the FBP
CONTROL
TOP GATE
CONTROL
REF
V
OUT
.
OUT1 OUT2
FBP
8
V
OUT
) accord-
7
8415 BD
8415f