LT1936 Datasheet, PDF (6/20 Pages) Linear Technology – 1.4A, 500kHz Step-Down Switching Regulator

LT1936
PI FU CTIO S
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 feed-
back 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 Appli-
cations Information. 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 floating.
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.
BLOCK DIAGRA
V_IN
2 ^VIN
C2
INT REG
AND
UVLO
ON OFF
R3
SHDN
5
C4
6
Σ
SLOPE
COMP
OSC
FREQUENCY
FOLDBACK
RQ
SQ
V_C
7
R4
C5
V_C
g_m
R_C
C_C
150pF
50k
COMP
8
1.200V
GND
4
DRIVER
BOOST
1
Q1
SW
3
FB
6
D2
C3
L1
D1
V_OUT
C1
R1
R2
1936 BD
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