SULR1221 Datasheet, PDF (12/17 Pages) Sangdest Microelectronic (Nanjing) Co., Ltd – Ultra LDO 2A Linear Regulator With Adjustable & Bypass Pin

Technical Data
Data Sheet N1579, Rev. -
SULR1221
Ultra LDO 2A Linear Regulator With Adjustable & Bypass Pin
Application Information
The SULR1221 is a high performance linear regulator that provides low-dropout voltage and low quiescent-
current. The device is available in an adjustable version and fixed output voltages ranging from 0.8V to 5.5V,
and the device can supply loads up to 2A.
SHUTDOWN __
By connecting EN(EN) pin to VIN(ground), the SULR1221 can be shut down to reduce the supply current to
0.01μA(typ.). At this operation mode, the output voltage of SULR1221 is equal to 0V.
CURRENT LIMIT
The SULR1221 includes a current limiter, which monitors and controls the maximum output current. If the
output is overloaded or shorted to ground, this can protect the device from being damaged.
THERMAL PROTECTION
The SULR1221 includes a thermal-limiting circuit, which is designed to protect the device against overload
condition. When the junction temperature exceeds TJ=150ºC, the thermal-limiting circuit turns off the pass
transistor and allows the IC to cool. For continuous load condition, maximum rating of junction temperature
must not be exceeded.
INPUT-OUTPUT CAPACITORS
Linear regulators require input and output capacitors to maintain stability. Input capacitor at a 4.7μF Output
capacitor with a 4.7μF or 10μF (Vout <1.8V, 10μF Cout is recommended) ceramic output capacitor is
recommended. When choosing the input and output ceramic capacitors, X5R and X7R types are
recommended because they retain their capacitance over wider ranges of voltage and temperature than other
types.
NOISE BYPASS CAPACITOR
A 22nF bypass capacitor at BP pin can reduce output voltage noise. The bypass pin can be floating if it’s
unnecessary.
OUTPUT VOLTAGE PROGRAMMING
Its internal feedback resistors can set the output voltage of SULR1221 linear regulator when the ADJ pin is
grounded. In addition, the output voltage of SULR1221 linear regulator can be set by the external feedback
resistors when connecting a resistive divider R1 and R2. While connecting a resistive divider, VOUT can be
calculated as:
R₁
V_OUT = 0.7×{1+
}
R₂
The resistive divider should sit as close to ADJ pin as possible.
POWER DISSIPATION
The maximum power dissipation of SULR1221 depends on the thermal resistance of its case and circuit
board, the temperature difference between the die junction and ambient air, and the rate of airflow. The rate
of temperature rise is greatly affected by the mounting pad configuration on the PCB, the board material, and
the ambient temperature. When the IC mounting with good thermal conductivity is used, the junction
temperature will be low even when large power dissipation applies.
The power dissipation across the device is P = I (V -V ).
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