lt3685emse-trpbf Linear Technology Corporation, lt3685emse-trpbf Datasheet - Page 7

• Manufacturer Part Number: lt3685emse-trpbf
• Description: 38v, 2a, 2.4mhz Step-down Switching Regulator
• Manufacturer: Linear Technology Corporation

PI FU CTIO S
BLOCK DIAGRA
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
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
LT3685 in shutdown mode. Tie to ground to shut down
the LT3685. Tie to 2.5V or more for normal operation. If
the shutdown feature is not used, tie this pin to the V
pin. RUN/SS also provides a soft-start function; see the
Applications Information section.
IN
U
(Pin 4): The V
V
IN
U
R
T
C1
10
4
5
7
6
V
RUN/SS
R
SYNC
PG
IN
IN
T
pin supplies current to the LT3685’s
SOFT-START
U
GND
11
W
INTERNAL 0.79V REF
+
–
R2
0.7V
8
FB
R1
ERROR AMP
+
–
Σ
200kHz–2.4MHz
SLOPE COMP
OSCILLATOR
–
+
IN
SYNC (Pin 6): This is the external clock synchronization
input. Ground this pin when SYNC function is not used. Tie
to a clock source for synchronization. Clock edges should
have rise and fall times faster than 1μs. 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 14% of the fi nal regulation voltage. PG output is
valid when V
FB (Pin 8): The LT3685 regulates the FB pin to 0.790V.
Connect the feedback resistor divider tap to this pin.
V
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.
R
to ground from this pin sets the switching frequency.
Exposed Pad (Pin 11): Ground. The Exposed Pad must
be soldered to PCB.
C
T
(Pin 10): Oscillator Resistor Input. Connecting a resistor
(Pin 9): The V
V
R
S
SWITCH
C
LATCH
CLAMP
Q
IN
is above 3.6V and RUN/SS is high.
C
pin is the output of the internal error
BOOST
SW
BD
V
C
1
2
3
9
D1
C
R
C
C
C3
L1
C
F
C2
LT3685
3685 BD
V
OUT
7
3685f