UM36550S Datasheet, PDF (7/10 Pages) Union Semiconductor, Inc. – 300mA, Micropower, VLDO Linear Regulator

UM365XX
Applications Information
The UM365XXS series are 300mA very low dropout regulators with micropower quiescent
current . The maximum dropout is only 90mV at the load current of 150mA. Output voltage noise
is as low as 100μV_RMS over a 10Hz to 100kHz bandwidth.
In addition to the low quiescent current, the UM365XXS regulators incorporate several protection
features which make them ideal for use in battery-powered systems. The devices are protected
against both reverse input voltages and reverse voltages from output to input (reverse current
protection). The devices also include current limit and thermal overload protection, and will
survive an output short circuit indefinitely. The fast transient response over comes the traditional
tradeoff between dropout voltage, quiescent current and load transient response inherent in most
regulators by using a proprietary new architecture.
Output Capacitance and Transient Response
The UM365XXS regulators are designed to be stable with a wide range of output capacitors. The
ESR of the output capacitor affects stability, most notably with small capacitors. A minimum
output capacitor of 1μF with an ESR of 0.3Ω or less is recommended to ensure stability. The
UM365XXS series are micropower devices and output transient response will be a function of
output capacitance. Larger values of output capacitance decrease the peak deviations and provide
improved transient response for larger load current changes. The shaded region of Figure 1 defines
the region over which the UM365XXS regulators are stable. The maximum ESR allowed is 0.3Ω.
High ESR tantalum and electrolytic capacitors may be used, but a low ESR ceramic capacitor
must be in parallel at the output. There is no minimum ESR requirement.
Figure 1
Extra consideration must be given to the use of ceramic capacitors. Ceramic capacitors are
manufactured with a variety of dielectrics, each with different behavior across temperature and
applied voltage. The most common dielectrics used are Z5U, Y5V, X5R and X7R. The Z5U and
Y5V dielectrics are good for providing high capacitances in a small package, but exhibit strong
voltage and temperature coefficients as shown in Figures 2 and 3. When used with a 5V regulator,
a 10μF Y5V capacitor can exhibit an effective value as low as 1μF to 2μF over the operating
temperature range. The X5R and X7R dielectrics result in more stable characteristics and are more
suitable for use as the output capacitor. The X7R type has better stability across temperature,
while the X5R is less expensive and is available in higher values.
________________________________________________________________________
http://www.union-ic.com Rev.01 Nov.2010
7/10