LT1936
6
1936fd
BLOCK DIAGRAM
PIN FUNCTIONS
BOOST (Pin 1): The BOOST pin is used to provide a drive
voltage, higher than the input voltage, to the internal bipolar
NPN power switch.
V
IN
(Pin 2): The V
IN
pin supplies current to the LT1936’s
internal regulator and to the internal power switch. This
pin must be locally bypassed.
SW (Pin 3): The SW pin is the output of the internal power
switch. Connect this pin to the inductor, catch diode and
boost capacitor.
GND (Pin 4): Tie the GND pin to a local ground plane
below the LT1936 and the circuit components. Return the
feedback divider to this pin.
SHDN (Pin 5): The SHDN pin is used to put the LT1936 in
shutdown mode. Tie to ground to shut down the LT1936.
Tie to 2.3V or more for normal operation. If the shutdown
feature is not used, tie this pin to the V
IN
pin. SHDN also
provides a soft-start function; see the Applications Infor-
mation. Do not drive SHDN more than 5V above V
IN
.
FB (Pin 6): The LT1936 regulates its feedback pin to
1.200V. Connect the feedback resistor divider tap to this
pin. Set the output voltage according to V
OUT
= 1.200V
(1 + R1/R2). A good value for R2 is 10k.
V
C
(Pin 7): The V
C
pin is used to compensate the LT1936
control loop by tying an external RC network from this pin
to ground. The COMP pin provides access to an internal
RC network that can be used instead of the external
components.
COMP (Pin 8): To use the internal compensation network,
tie the COMP pin to the V
C
pin. Otherwise, tie COMP to
ground or leave it fl oating.
Exposed Pad (Pin 9): The Exposed Pad must be soldered
to the PCB and electrically connected to ground. Use a
large ground plane and thermal vias to optimize thermal
performance.
4
∑
R
DRIVER
Q1
S
OSC
SLOPE
COMP
FREQUENCY
FOLDBACK
INT REG
AND
UVLO
V
C
g
m
1.200V
1936 BD
8
2
5
Q
Q
1
3
BOOST
SW
6
FB
GND
R
C
50k
C
C
150pF
V
OUT
R1
R2
L1
D2
C3
C1
D1
V
IN
C2
V
IN
ON OFF
COMP
7
V
C
R4
C5
C4
R3
SHDN
