Micrel, Inc.
MAQ5283
Detailed Description
The MAQ5283 voltage regulator accepts a 6V to 120V
input voltage and has an ultra-low 8µA typical quiescent
current while offering an excellent line transient response
and PSRR. These features make it ideal for harsh, noisy
environments. All options offer 150mA of output current.
The MAQ5283YME offers an adjustable output voltage
from 1.23V to 5.5V. The MAQ5283-3.3YME offers a fixed
3.3V output and the MAQ5283-5.0YME offers a fixed 5.0V
output. The YME packaged devices feature a heat slug to
remove heat from the die more effectively.
Output Voltage Setting
For the MAQ5283YME, V
OUT
is programmable from 1.23V
to 5.5V using an external resistive divider. V
OUT
is set
using the following equation:
⎛
R1
⎞
V
OUT
=
V
REF
× ⎜
+
1
⎟
⎝
R2
⎠
Eq. 1
Applications Information
Thermal Protection
The MAQ5283 has internal thermal shutdown 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 results in a cycled output during continuous
thermal-overload conditions.
Current Limit
The MAQ5283 features output current-limit protection. The
output sustains a continuous short circuit to GND without
damage to the device, but thermal shutdown often results.
The typical value for the current limit of the MAQ5283 is
300mA.
Input Capacitor
Connect a 1.0µF capacitor from VIN to GND. Micrel
recommends the C5750X7R2E105M, 1.0µF, 250V
capacitor made by TDK. When using a different capacitor,
make sure that the voltage rating of the capacitor has
enough headroom to withstand any potential transient.
CPSRR Capacitor
To maintain high power supply rejection, connect a 0.1µF
capacitor from CPSRR to GND. The voltage rating of the
capacitor must be at least 14V.
Output Capacitor
Connect a 10µF capacitor from VOUT to GND. Make sure
that the voltage rating of the capacitor is greater than the
designed output voltage of the MAQ5283.
where V
REF
= 1.228V, and R1 and R2 form the feedback
voltage divider from V
OUT
to ground.
Thermal Measurements
It is always a good idea to measure an IC’s case
temperature to make sure that it is within operating limits,
but it is easy to get false results. The standard
thermocouple that comes with many voltage meters uses a
large wire gauge that behaves like a heat-sink. This
causes 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 a 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,
which is 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 2012
8
M9999-100912-A
MICREL [ MICREL SEMICONDUCTOR ]
