MIC5280 Datasheet, PDF (9/14 Pages) Micrel Semiconductor – 25mA, 120V, Low IQ, High PSRR LDO

Micrel, Inc.
Functional Description
MIC5280 is a high performance linear regulator which
accepts wide input operating range 4.5V to 120V. This
allows the use in harsh environments. The input can
surge from 0V to 120V within a millisecond. The first
stage bypass regulator isolates output from this input by
producing an intermediate head voltage which is a input-
to-post regulator. This post regulator gives the control to
regulate the required output voltage. The output voltage
is adjustable from 1.22V to 5V.
VIN Pin
V_IN pin is the supply input pin. A 0.18µF or larger
capacitor with proper voltage rating is recommended for
filtering the input voltage variations and noise on the
input voltage. This capacitor should be close to the V_IN
and GND pins.
CBYP Pin
The Bypass pin is the output of the Bypass regulator and
the input of the post regulator. By connecting a capacitor
from the C_BYP pin-to-GND, a greater stability and a much
higher PSRR is achieved. A 10µF ceramic capacitor is
recommended and this significantly decreases V_OUT
noise and perturbations due to line transients. When the
MIC5280 is enabled, the Bypass pin voltage is regulated
at 5.5V. To maintain 5.5V regulation and high PSRR, the
V_IN must be no lower than 6.5V. For V_IN less than 6.5V
while in dropout, the PSRR is reduced.
MIC5280
EN Pin
EN pin is a logic level enable input which turns MIC5280
on/off. Drive EN pin level high to turn the device ON and
drive EN pin low to keep the device in shutdown mode.
In shutdown mode the MIC5280 draws typically 20nA
from the input supply. EN pin can withstand 120V,
allowing EN always connected to input supply for
always-ON operation.
ADJ Pin
ADJ pin gives the flexibility to set the output voltage to
the requirement from 1.22V to 5V. Use a resistor divider
from output and connect to ADJ pin, internal reference is
typically 1.219V.
GND Pin
This GND pin provides the ground for all the electrical
connections. MIC5280 has exposed pad underneath the
package which should be connected to ground. If this
exposed pad is connected to wide ground plane it would
improve the thermal performance of MIC5280.
NC Pins
There are two NC pins on the package which are not
connected internally.
VOUT Pin
The V_OUT pin is the regulated output of the post
regulator. When the MIC5280 is enabled, V_OUT regulates
at a fixed voltage, when disabled, V_OUT is high
impedance. A 2.2µF or larger ceramic capacitor must be
connected to V_OUT pin-to-ground.
January 2009
9
M9999-012209-A