MAQ5281 データシートの表示（PDF） - Micrel
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MAQ5281 Datasheet PDF : 16 Pages
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Micrel, Inc.
MAQ5281
Detailed Description
The MAQ5281 voltage regulator accepts a 6V to 120V
input and has an ultra-low 6µA typical quiescent current
while offering an excellent line transient response and
PSRR. These features make it ideal for harsh, noisy
environments. All options of the device offer 25mA of
output current. The MAQ5281YMME offer an adjustable
output voltage from 1.27V to 5.5V. The MAQ5281-
3.3YMME offer fixed 3.3V outputs and the MAQ5281-
5.0YMME offer fixed 5.0V outputs. The YMME packaged
devices feature a heat slug to more effectively remove
heat from the die.
Applications Information
Thermal Protection
The MAQ5281 has an internal thermal shutdown circuit to
protect it from excessive heating of the die. When the
junction temperature exceeds approximately +155°C, the
output is disabled and the device begins to cool down. The
device turns back on when the junction temperature cools
by 15°C. This will result in a cycled output during
continuous thermal-overload conditions.
Current Limit
The MAQ5281 features output current-limit protection. The
output sustains a continuous short circuit to GND without
damage to the device, but thermal shutdown often results.
Input Capacitor
Connect a 1µF capacitor from VIN to GND. Micrel
recommends the C5750X7R2E105M, 1µF, 250V capacitor
made by TDK. When using a different capacitor, assure
that the voltage rating of the capacitor exceeds any
potential transient.
CPSRR Capacitor
Connect a 0.1µF capacitor from CPSRR to GND to
maintain high power supply rejection. The voltage rating of
the capacitor must be at least 14V.
Output Capacitor
Connect a 10µF capacitor from VOUT to GND. Assure that
the voltage rating of the capacitor exceeds the designed
output voltage of the MAQ5281.
Output Voltage Setting
For the MAQ5281YMME, VOUT is programmed from 1.27V
to 5.5V using:
VOUT
=
VREF
× R1 +1
R2
where VREF = 1.27V, and R1 and R2 are shown in the
Typical Applications circuit.
Thermal Measurements
It is always wise to measure an IC’s case temperature to
make sure that it is within operating limits, but it is easy to
get erroneous results. The standard thermocouple that
comes with many voltage meters uses a large wire gauge
that behaves like a heat-sink, resulting in artificially low
case temperature measurements. Use a thermocouple of
36-gauge wire or smaller, such as the Omega (5SC-TT-K-
36-36), to minimize the heat-sinking effect. Also, apply
thermal compound to maximize heat transfer between the
IC and the thermocouple.
An infrared thermometer is a recommended alternative.
The IR thermometer from Optris has a 1mm spot size,
ideal for monitoring small surface mount packages. Also,
the optional stand makes it easy to keep the beam on the
IC for long periods of time.
October 2, 2014
9
Revision 2.0
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