LTM8029
8
8029fd
For more information www.linear.com/LTM8029
PIN FUNCTIONS
V
IN
(Bank 1): The V
IN
pins supply current to the LTM8029’s
internal regulator and to the internal power switch. This
pin must be locally bypassed with an external, low ESR
capacitor; see Table 1 for recommended values.
V
OUT
(Bank 3): Power Output Pins. Apply the output filter
capacitor and the output load between these pins and
GND pins.
GND (Bank 2): Tie these GND pins to a local ground plane
below the LTM8029 and the circuit components. In most
applications the bulk of the heat flow out of the LTM8029
is through these pads, so the printed circuit design has a
large impact on the thermal performance of the part. See
the PCB Layout and Thermal Considerations sections for
more details. Return the feedback resistor (R
FB
) to this net.
RUN (Pin A1): Pull the RUN pin below 0.95V to shut down
the LTM8029. Tie to 1.3V or more for normal operation.
If the shutdown feature is not used, tie this pin to V
IN
.
FB (Pin A2): The LTM8029 regulates its FB pin to 1.2V.
Connect the output feedback resistor from this pin to
ground. The value of R
FB
is given by the equation R
FB
=
1200/(V
OUT
– 1.2), where R
FB
is in kΩ.
RT (Pin B1): The RT pin is used to program the switching
frequency of the LTM8029 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.
PGOOD (Pin B2): The PGOOD pin is the open-collector
output of an internal comparator that monitors the FB pin.
PGOOD remains low until the FB pin is within 10% of the
final regulation voltage. PGOOD output is valid when V
IN
is above 4.5V and RUN is high. If this function is not used,
leave this pin floating.
BIAS (Pin H3): The BIAS pin powers internal circuitry.
Connect to a power source greater than 2.25V and less
than 20V. If the output is greater than 2.25V, connect this
pin there. Also, make sure that BIAS + V
IN
is less than 55V.
