Datasheet
LT3693
7
3693f
PI FU CTIO S
UUU
BD (Pin 1): This pin connects to the anode of the boost
Schottky diode. BD also supplies current to the internal
regulator.
BOOST (Pin 2): This pin is used to provide a drive
voltage, higher than the input voltage, to the internal bipolar
NPN power switch.
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.
V
IN
(Pin 4): The V
IN
pin supplies current to the LT3693’s
internal regulator and to the internal power switch. This
pin must be locally bypassed.
RUN/SS (Pin 5): The RUN/SS pin is used to put the
LT3693 in shutdown mode. Tie to ground to shut down
the LT3693. Tie to 2.5V or more for normal operation. If
the shutdown feature is not used, tie this pin to the V
IN
pin. RUN/SS also provides a soft-start function; see the
Applications Information section.
SYNC (Pin 6): This is the external clock synchronization
input. Ground this pin when not used. Tie to a clock source
for synchronization. Clock edges should have rise and
fall times faster than 1μs. Do not leave pin fl oating. See
synchronizing section in Applications Information.
PG (Pin 7): The PG pin is the open collector output of an
internal comparator. PG remains low until the FB pin is
within 9% of the fi nal regulation voltage. PG output is valid
when V
IN
is above 3.6V and RUN/SS is high.
FB (Pin 8): The LT3693 regulates the FB pin to 0.790V.
Connect the feedback resistor divider tap to this pin.
V
C
(Pin 9): The V
C
pin is the output of the internal error
amplifi er. The voltage on this pin controls the peak switch
current. Tie an RC network from this pin to ground to
compensate the control loop.
RT (Pin 10): Oscillator Resistor Input. Connecting a resistor
to ground from this pin sets the switching frequency.
Exposed Pad (Pin 11): Ground. The Exposed Pad must
be soldered to PCB.
BLOCK DIAGRA
W
+
–
+
–
+
–
OSCILLATOR
200kHzTO2.4MHz
V
C
CLAMP
SOFT-START
SLOPE COMP
R
V
IN
V
IN
RUN/SS
BOOST
SW
SWITCH
LATCH
V
C
V
OUT
C2
C3
C
F
L1
D1
C
C
R
C
BD
RT
R2
GND
ERROR AMP
R1
FB
R
T
C1
PG
0.7V
S
Q
5
3693 BD
4
5
10
7
1
2
3
9
11 8
6
INTERNAL 0.79V REF
SYNC
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