mic39151 Micrel Semiconductor, mic39151 Datasheet - Page 10

• Manufacturer Part Number: mic39151
• Description: Mic39150/mic39151 1.5a Low-voltage Low-dropout Regulator
• Manufacturer: Micrel Semiconductor

Transient Response and 3.3V to 2.5Vor 2.5V to 1.8V
Conversion
The MIC39150/1 has excellent transient response to
variations in input voltage and load current. The device
has been designed to respond quickly to load current
variations and input voltage variations. Large output
capacitors are not required to obtain this performance. A
standard 10µF output capacitor, preferably tantalum, is
all that is required. Larger values help to improve
performance even further.
By virtue of its low-dropout voltage, this device does not
saturate into dropout as readily as similar NPN-based
designs. When converting from 3.3V to 2.5V, or 2.5V to
1.8V, the NPN-based regulators are already operating in
dropout, with typical dropout requirements of 1.2V or
greater. To convert down to 2.5V without operating in
dropout, NPN-based regulators require an input voltage
of 3.7V at the very least. The MIC39150/1 regulator will
provide excellent performance with an input as low as
3.0V or 2.5V, respectively. This gives the PNP-based
regulators a distinct advantage over older, NPN-based
linear regulators.
Minimum Load Current
The MIC39150 regulator is specified between finite
loads. If the output current is too small, leakage currents
dominate and the output voltage rises. A 10mA minimum
load current is necessary for proper regulation.
Micrel, Inc.
May 2006
10
Error Flag
The MIC39151 version features an error flag circuit
which monitors the output voltage and signals an error
condition when the voltage 5% below the nominal output
voltage. The error flag is an open-collector output that
can sink 10mA during a fault condition.
Low output voltage can be caused by a number of
problems, including an overcurrent fault (device in
current limit) or low input voltage. The flag is inoperative
during overtemperature shutdown.
When the error flag is not used, it is best to leave it
open. The flag pin can be tied directly to pin 4, the output
pin.
Enable Input
The MIC39151 version features an enable input for
on/off control of the device. Its shutdown state draws
“zero” current (only microamperes of leakage). The
enable input is TTL/CMOS compatible for simple logic
interface, but can be connected to up to 20V. When
enabled, it draws approximately 15µA.
MIC39150/39151
[phone]
M9999-053106