ltm8021 Linear Technology Corporation, ltm8021 Datasheet - Page 6

• Manufacturer Part Number: ltm8021
• Description: 36vin, 500ma Step-down Dc/dc ?module
• Manufacturer: Linear Technology Corporation

PIN FUNCTIONS
LTM8021
V
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
connected from V
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
than 3V otherwise. When BIAS > 3V the internal circuitry
will be powered from this pin to improve effi ciency. Main
regulator power will still come from V
RUN/SS (Pin A1): Tie RUN/SS pin to ground to shut down
the LTM8021. Tie to 1.6V or more for normal operation.
BLOCK DIAGRAM
6
IN
OUT
OUT
(Bank 1): The V
(Bank 2): Power Output Pins. An external capacitor is
when V
OUT
V
RUN/SS
IN
OUT
> 3V or to another DC voltage greater
IN
pin supplies current to the LTM8021’s
to GND in most applications. Apply
0.1μF
CURRENT MODE
CONTROLLER
IN
GND
.
If the shutdown feature is not used, tie this pin to the V
pin. The RUN/SS also provides soft-start and frequency
foldback. To use the soft-start function, connect a resis-
tor and capacitor to this pin. Do not allow the RUN/SS
pin to rise above V
section.
GND (Bank 3): The GND connections serve as the main
signal return and the primary heatsink 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
R
ADJ
= 80/(V
OUT
10μH
– 0.8), where R
IN
ADJ
. See the Applications Information
15pF
ADJ
100k
1%
is given by the equation,
ADJ
is in k.
10μF
V
BIAS
OUT
8021 BD
8021fa
IN