LTM8031
6
8031fb
Typical perForMance characTerisTics
Radiated Emissions Radiated Emissions
T
A
= 25°C, unless otherwise noted.
pin FuncTions
V
IN
(Bank 3): The V
IN
pin supplies current to the LTM8031’s
internal regulator and to the internal power switch. This
pin must be locally bypassed with an external, low ESR
capacitor of at least 1µF .
FIN (K3, L3): Filtered Input. This is the node after the input
EMI filter. Use this only if there is a need to modify the
behavior of the integrated EMI filter or if V
IN
rises or falls
rapidly; otherwise, leave these pins unconnected. See the
Applications Information section for more details.
GND (Bank 2): Tie these GND pins to a local ground plane
below the LTM8031 and the circuit components. Return
the feedback divider (R
ADJ
) to this net.
V
OUT
(Bank 1): Power Output Pins. Apply the output filter
capacitor and the output load between these pins and
GND pins.
AUX (Pin H5): Low Current Voltage Source for BIAS. In
many designs, the BIAS pin is simply connected to V
OUT
.
The AUX pin is internally connected to V
OUT
and is placed
adjacent to the BIAS pin to ease printed circuit board rout-
ing. Although this pin is internally connected to V
OUT
, do
not connect this pin to the load. If this pin is not tied to
BIAS, leave it floating.
BIAS (Pin H4): The BIAS pin connects to the internal power
bus. Connect to a power source greater than 2.8V. If the
output is greater than 2.8V, connect this pin to AUX. If the
output voltage is less, connect this to a voltage source
between 2.8V and 25V. Also, make sure that BIAS + V
IN
is less than 56V.
RUN/SS (Pin L5): Pull RUN/SS pin to less than 0.2V to
shut down the LTM8031. 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.
RT (Pin G7): The RT pin is used to program the switching
frequency of the LTM8031 by connecting a resistor from
this pin to ground. The Applications Information section of
the data sheet includes a table to determine the resistance
value based on the desired switching frequency. Minimize
capacitance at this pin.
SHARE (Pin H7): Tie this to the SHARE pin of another
LTM8031 when paralleling the outputs.
FREQUENCY (MHz)
0
50
70
90
V
IN
= 36V
V
OUT
= 10V AT 1A
800
8031 G19
30
10
40
60
80
20
0
–10
200100
400300
600 700 900
500
1000
EN55022
CLASS B
LIMIT
FREQUENCY (MHz)
0
50
70
90
V
IN
= 36V
V
OUT
= 2.5V AT 1A
800
8031 G20
30
10
40
60
80
20
0
–10
200100
400300
600 700 900
500
1000
EN55022
CLASS B
LIMIT
