ADP1720-ADJ Analog Devices, ADP1720-ADJ Datasheet - Page 7

• Manufacturer Part Number: ADP1720-ADJ
• Description: 50mA High-Voltage Micro-power LDO in MSOP
• Manufacturer: Analog Devices

PRELIMINARY TECHNICAL DATA
THEORY OF OPERATION
Introduction
The ADP1720 is a high-voltage, micro-power, low dropout
linear regulator. Designed for robust operation, the ADP1720
includes current limiting and short-circuit protection, thermal
overload protection. With just 25µA of quiescent supply current
and a micro-power shutdown mode, this device is ideal for
applications that require low quiescent current. The small
thermally-enhanced MSOP package and 1µF ceramic output
capacitor provides a compact solution with low thermal
resistance for high power dissipation.
The ADP1720 is available in fixed output voltages of 3.3V and
5V, or its output voltage is adjustable over a range of 1.2V to
5V. The ADP1720 operates over the -40°C to 125°C ambient
temperature range.
Adjustable Output Voltage
The ADP1720 output voltage is adjustable over a 1.2V to 5.0
range. The output voltage is set by connecting a resistive
voltage divider from OUT to ADJ. The output voltage is
calculated using the equation VOUT=1.2V(1+R
where R
resistor from ADJ to GND. The maximum bias current into
ADJ is 100nA, so for less than 0.1% error due to the bias
current, use values less than 12k for R
Output Capacitor Selection
The ADP1720 is optimized for operation with small 1µF
ceramic capacitors. The ADP1720 maintains stability with
capacitance greater than 1 F, 10uF maximum and over a wide
range of capacitor ESR values ( At least 1m to 100m ).
TOP
is the resistor from OUT to ADJ and R
BOTTOM
.
TOP
BOTTOM
/R
BOTTOM
Rev. PrA | Page 7 of 9
is the
)
Ceramic capacitors are manufactured with a variety of
dielectrics, each with different behavior over temperature and
applied voltage. When choosing your capacitor be sure to
choose a dielectric adequate to ensure the minimum
capacitance over the necessary temperature range.
Thermal Protection
The ADP1720 has an internal thermal shutdown function that
protects itself from thermal overloads. The thermal protection
circuitry activates and disables the output when the die
temperature exceeds 150°C. The thermal protection circuitry
has a typical hysteresis of 15°C. Once the die temperature
decreases beyond the hysteresis, the output is enabled again.
Current Limit
The ADP1720 uses internal current limiting to protect itself and
its load during overload and short-circuit conditions.
Shutdown
The ADP1720 enters a low power shutdown state by driving
EN to GND. In shutdown, the ADP1720 consumes less than
5 A. For automatic startup connect EN to IN. Note that EN
withstands up to the +28V input voltage without damage.
Package and Power Dissipation
The ADP1720 use a thermally-enhanced MSOP package,
which achieves a respectable TBD°C/W for such a small
footprint.
ADP1720