MIC5234_11 Datasheet, PDF (9/16 Pages) Micrel Semiconductor – Low-Quiescent Current 150mA LDO Regulator

Micrel, Inc.
Application Information
The MIC5234 is a µcap low dropout linear regulator
which provides wide input voltage range, reversed-
battery protection, reduced quiescent current and small
package. When disabled, the quiescent current is
reduced to 0.1μA.
Enable
A low on the enable pin disables the part, forcing the
quiescent current to less than 0.1μA. Thermal shutdown
is not functional while the device is disabled. The
maximum enable bias current is 2μA for a 2.0V input. An
open collector pull-up resistor tied to the input voltage
should be set low enough to maintain 2V on the enable
input. Figure 1 shows an open collector output driving
the enable pin through a 200k pull-up resistor tied to the
input voltage. In order to avoid output oscillations, slow
transitions from low to high should be avoided.
Figure 1. Remote Enable
Input Capacitor
An input capacitor may be required when the device is
not near the source power supply or when supplied by a
battery. Small, surface mount, ceramic capacitors can be
used for bypassing. Larger values may be required if the
source supply has high ripple.
Output Capacitor
The MIC5234 has been designed to minimize the effect
of the output capacitor ESR on the closed loop stability.
As a result, ceramic or film capacitors can be used at the
output. Figure 2 displays a range of ESR values for a
10μF capacitor. A 10μF capacitor with an ESR less than
3.4Ω is sufficient for stability over the entire input voltage
range. Stability can also be maintained throughout the
specified load and line conditions with 2.2μF film or
ceramic capacitors.
MIC5234
Figure 2. Output Capacitor ESR
Reverse Current Protection
The MIC5234 is designed to limit the reverse current
flow from output to input in the event that the MIC5234
output has been tied to the output of another power
supply. Refer to the Typical Characteristics to see the
graphs detailing the reverse current flow with the input
grounded and open.
Thermal Shutdown
The MIC5234 has integrated thermal protection. This
feature is only for protection purposes. The device
should never be intentionally operated near this
temperature as this may have detrimental effects on the
life of the device. The thermal shutdown may become
inactive while the enable input is transitioning a high to a
low. When disabling the device via the enable pin,
transition from a high to low quickly. This will insure that
the output remains disabled in the event of a thermal
shutdown.
ePad SOIC-8 Thermal Characteristics
The MIC5234 is a high input voltage device intended to
provide 150mA of continuous output current in one a
small profile package. The ePad SOIC-8 allows the
device to dissipate approximately 50% more power than
the SOIC-8 package.
The benefit of the MIC5234 ePad SOIC-8 package is an
improvement to less than half the thermal resistance
over the standard SO-8 packing. Lower thermal
resistance means more output current or higher input
voltage for a given package size. Lower thermal
resistance is achieved by joining the die with the die
attach paddle to create a single piece electrical and
thermal conductor. This concept has been used by
MOSFET manufacturers for years, proving very reliable
and cost effective for the user. Thermal resistance
consists of two main elements, θ_JC (junction-to-case
thermal resistance) and θ_CA (case-to-ambient thermal
resistance). See Figure 3. θ_JC is the resistance from the
die to the case (ePad) of the package. θ_CA is the
September 2011
9
M9999-092711-B