LTM8021
6
8021fd
pin FuncTions
V
IN
(Bank 1):
The V
IN
pin supplies current to the LTM8021’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.
V
OUT
(Bank 2):
Power Output Pins. An external capacitor is
connected from V
OUT
to GND in most applications. Apply
output load between these pins and GND pins.
BIAS (Pin H3):
The BIAS pin connects to the internal
boost Schottky diode and to the internal regulator. Tie to
V
OUT
when V
OUT
> 3V or to another DC voltage greater
than 3V otherwise. When BIAS > 3V the internal circuitry
will be powered from this pin to improve efficiency. Main
regulator power will still come from V
IN
.
RUN/SS (Pin A1):
Tie RUN/SS pin to ground to shut down
the LTM8021. Tie to 1.6V or more for normal operation.
If the shutdown feature is not used, tie this pin to the V
IN
pin. The RUN/SS also provides soft-start and frequency
foldback. To use the soft-start function, connect a resistor
and capacitor to this pin. Do not allow the RUN/SS pin to
rise above V
IN
. See the Applications Information section.
GND (Bank 3):
The GND connections serve as the main
signal return and the primary heat sink for the LTM8021. Tie
the GND pins to a local ground plane below the LTM8021
and the circuit components. Return the feedback divider
to this signal.
ADJ (Pin A2):
The LTM8021 regulates its ADJ pin to
0.8V. Connect the adjust resistor from this pin to ground.
The value of R
ADJ
is given by the equation, R
ADJ
= 80/
(V
OUT
– 0.8), where R
ADJ
is in k.
V
IN
8021 BD
BIAS
CURRENT MODE
CONTROLLER
V
OUT
10µF
15pF
10µH
0.1µF
RUN/SS
100k
1%
ADJ
GND
block DiagraM