LT1936 Linear Technology, LT1936 Datasheet - Page 6

• Manufacturer Part Number: LT1936
• Description: 1.4A 500kHz Step-Down Switching Regulator
• Manufacturer: Linear Technology

PIN FUNCTIONS
BLOCK DIAGRAM
LT1936
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
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
provides a soft-start function; see the Applications Infor-
mation. Do not drive SHDN more than 5V above V
6
IN
(Pin 2): The V
ON OFF
V
IN
R3
C2
C4
2
5
V
IN
SHDN
IN
pin supplies current to the LT1936’s
INT REG
UVLO
AND
OSC
FREQUENCY
FOLDBACK
7
SLOPE
COMP
R4
V
C5
C
IN
∑
8
pin. SHDN also
V
50k
COMP
R
C
C
150pF
C
C
IN
g
m
.
R
S
4
GND
Q
Q
1.200V
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
(1 + R1/R2). A good value for R2 is 10k.
V
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
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.
C
(Pin 7): The V
DRIVER
C
pin is used to compensate the LT1936
Q1
C
BOOST
pin. Otherwise, tie COMP to
SW
FB
1
3
6
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1936 BD
C3
D1
L1
D2
OUT
C1
= 1.200V
R1
R2
V
OUT
1936fd