lt3695 Linear Technology Corporation, lt3695 Datasheet - Page 23

• Manufacturer Part Number: lt3695
• Description: 1a Fault Tolerant Micropower Step-down Regulator
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
Table 6: Effects of Floating Pins
PIN
PGND
DA
SW
RUN/SS
RT
SYNC
V
V
FB
PG
GND
BD
BOOST
For the best fault tolerance to inadvertent adjacent pin
shorts, the RUN/SS pin must not be directly connected to
either ground or V
and SW then connecting RUN/SS to V
and would thus raise V
would tie SW to ground and would damage the power
switch if this is done when the power switch is on. A short
between RT and a RUN/SS pin that is connected to V
would violate the absolute maximum ratings of the RT pin.
Therefore, the current supplying the RUN/SS pin must be
limited, for example, with resistor R3 in Figure 10. In case
of a short between RUN/SS and SW this resistor charges
C2 through the inductor L1 if the current it supplies from
IN
C
EFFECT
No effect if the Exposed Pad is soldered.
Otherwise: V
provide a bypass resistor at the DA pin. See the following discussion.
V
resistor. See the following discussion.
V
V
V
V
pin is sensitive to noise which can degrade device performance.
V
V
performance. The output voltage ripple will increase if the part becomes unstable.
V
No effect.
Output maintains regulation, but potential degradation of device performance.
V
saturate properly, which increases its power dissipation.
V
cannot saturate properly, which increases its power dissipation.
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
may fall below regulation voltage. Make sure that V
will fall below regulation voltage.
will fall below regulation voltage.
will fall below regulation voltage.
may fall below regulation voltage. A fl oating SYNC pin confi gures the LT3695 for pulse-skipping mode. However, a fl oating SYNC
will fall below regulation voltage.
may fall below regulation voltage. Disconnecting the V
will fall below regulation voltage.
may fall below regulation voltage. If BD is not connected, the boost capacitor cannot be charged and thus the power switch cannot
may fall below regulation voltage. If BOOST is not connected, the boost capacitor cannot be charged and thus the power switch
IN
. If there was a short between RUN/SS
OUT
OUT
may fall below regulation voltage. Make sure that V
. Likewise, grounding RUN/SS
IN
would tie SW to V
IN
IN
IN
< V
C
pin alters the loop compensation and potentially degrades device
IN(MAX)
Figure 10. The Dashed Lines Show where a Connection Would
Occur if There Were an Inadvertent Short from RUN/SS to an
Adjacent Pin or from BOOST to BD. In These Cases, R3 Protects
Circuitry Tied to the RT or SW Pins, and D2 Shields BOOST from
V
OUT
220nF
IN
V
C
. If C
IN
47Ω
SS
R
(see Input Voltage Range section for details) and provide a bypass
< V
SS
IN(MAX)
SS
R3
is Used for Soft Start, R
R
T
(see Input Voltage Range section for details) and
RUN/SS
RT
V
IN
LT3695
BOOST
BD
SW
DA
FB
SS
R2
Isolates it from SW
C3 L1
D1
D2
R1
LT3695
C2
3695 F10
R
23
LOAD
V
OUT
3695f