10
LTC1911-1.5/LTC1911-1.8
1911f
APPLICATIO S I FOR ATIO
WUUU
is needed to ensure that minimum capacitance values are
met over operating temperature and bias voltage.
Table 1 is a list of ceramic capacitor manufacturers and
how to contact them.
Table 1. Ceramic Capacitor Manufacturers
AVX 1-(803)-448-1943 www.avxcorp.com
Kemet 1-(864) 963-6300 www.kemet.com
Murata 1-(800) 831-9172 www.murata.com
Taiyo Yuden 1-(800) 348-2496 www.t-yuden.com
Vishay 1-(800) 487-9437 www.vishay.com
Layout Considerations
Due to the high switching frequency and transient cur-
rents produced by the LTC1911, careful board layout is
necessary for optimal performance. A true ground plane
and short connections to all capacitors will optimize
performance, reduce noise and ensure proper regulation
over all conditions. Figure 3 shows the recommended
layout configuration.
Additional output filtering can be achieved by placing a
second output capacitor, connected to the ground plane,
about 2cm or more from the LTC1911 output capacitor
(C4). The inductance of the trace running to the second
output capacitor will significantly attenuate the high speed
switching transients of the LTC1911. Even small capaci-
tors as low as 0.1µF will provide excellent results.
Thermal Management
The power dissipation in the LTC1911 can cause the
junction temperature to rise at rates of up to 160°C/W. If
the specified operating conditions are followed, the junc-
tion temperature should never exceed the 160°C thermal
shutdown temperature. The junction temperature can
come very close and possibly exceed the specified 125°C
operating junction temperature. To reduce the maximum
junction temperature, a good thermal connection to the PC
board is recommended. Connecting the GND pin (Pin 4) to
a ground plane, and maintaining a solid ground plane
under the device on two layers of the PC board, can reduce
the thermal resistance of the package and PC board
considerably.
C1
1911 F03
C4
OUTGND
C2
V
IN
SS/SHDN
: CONNECT TO GND PLANE ON BACK OF BOARD
C3
U1
Figure 3. Recommended Component Placement and Grounding