UM4750_15 Datasheet, PDF (8/13 Pages) Union Semiconductor, Inc. – 300mA, Micropower, Dual Channel VLDO Linear Regulator

Typical Application Circuit
V_IN
C_IN
1µF
Chip Enable
UM4750
VIN
VOUT1
EN1
EN2
VOUT2
GND
C_OUT1
1µF
V_OUT1
C_OUT2
1µF
V_OUT2
Pin Function
VIN : Unregulated input supply. A small 1.0µF capacitor should be connected from VIN to GND.
GND : Ground and Heat Sink. Solder to a ground plane or large pad to maximize heat dissipation.
EN: Enable, Active High. This pin is used to put the UM4750 into shutdown. The EN pin cannot
be left floating and must be tied to the input pin if not used.
VOUT : Regulated Voltage Output.
Applications Information
The UM4750 series are 300mA very low dropout regulators with micropower quiescent current
and shutdown. The maximum dropout is only 200mV at the load current of 100mA. Output
voltage noise is as low as 200μV_RMS over a 10Hz to 100kHz bandwidth.
In addition to the low quiescent current, the UM4750 regulators incorporate several protection
features which make them ideal for use in battery-powered systems. Devices include current limit
and thermal overload protection.
Output Capacitance and Transient Response
The UM4750 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 UM4750
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. Extra consideration must be given to
the use of ceramic capacitors. 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.
Board Layout Recommendations to Improve PSRR and Noise Performance
To improve AC performance such as PSRR, output noise, and transient response, it is
recommended that the board be designed with separate ground planes for VIN and VOUT, with
each ground plane connected only at the GND pin of the device. In addition, the ground
connection for the output capacitor should connect directly to the GND pin of the device. High
ESR capacitors may degrade PSRR.
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http://www.union-ic.com Rev.07 Nov.2015
8/13