3-1. Glossary of terms used in the datasheets for LDO regulators

The following table provides the definitions of major electrical characteristics shown in the datasheets of LDO regulators.

Glossary of terms
Characteristic Symbol Description
Input voltage VIN VIN is the input voltage range in which an LDO regulator can operate properly.
Bias voltage VBIAS
VBAT		 VBIAS and VBAT are the bias voltage range in which an LDO regulator can operate properly. The bias voltage is used as a power supply for the internal control circuit.
Output voltage accuracy Output voltage VOUT VOUT is the accuracy of the minimum and maximum output voltage regulation relative to the typical value under the test conditions specified in a datasheet.
Adjustable voltage VADJ VADJ is the reference voltage for the internal error amplifier. VADJ is specified for LDO regulators whose output voltage can be adjusted arbitrarily with external resistors.
Quiescent current IB
IB(ON)		 IB and IB(ON) are the quiescent current of the internal circuitry minus the pull-down current of the CONTROL pin flowing out of the GND pin when an LDO regulator is operating under the test conditions specified in a datasheet.
Quiescent current IIN(ON) IIN(ON) is the quiescent current flowing into the VIN pin when an LDO regulator is operating under the test conditions specified in a datasheet.
Quiescent current IBIAS(ON) IBIAS(ON) is the quiescent current flowing into the VBIAS pin when an LDO regulator is operating under the test conditions specified in a datasheet.
Quiescent current

IB(OFF)

IIN(OFF)

IBIAS(ON)

 IB(OFF), IIN(OFF), and IBIAS(ON) are the current flowing through the VIN and VBIAS pins when an LDO regulator is in standby mode with VCT = 0 V.
Standby current IADJ IADJ is the input current to an error amplifier connected to the VADJ pin. IADJ is specified for LDO regulators whose output voltage can be adjusted arbitrarily with external resistors.
ADJ pin current VCT(ON) VCT(ON) is the voltage required at the CONTROL pin to turn on an LDO regulator. When a voltage in the range specified in a datasheet is applied to the CONTROL pin, output voltage appears at the VOUT pin.
Control voltage (ON) VCT(OFF) VCT(OFF) is the voltage required at the CONTROL pin to turn off an LDO regulator. When a voltage in the range specified in a datasheet is applied to the CONTROL pin, an LDO regulator shuts down.
Control voltage (OFF) ICT ICT is the current that flows through a pull-down device connected between the CONTROL and GND pins of an LDO regulator.
Line regulation

Reg･line

 Line regulation (Reg·line) is an amount of change of the output voltage (VOUT) with respect to the input voltage (VIN). LDO regulators with a smaller Reg·line value have a higher ability to maintain VOUT regulation despite changes to VIN. 
Load regulation Reg･load Load regulation (Reg·load) is an amount of change of the output voltage (VOUT) with respect to the output current (IOUT). LDO regulators with a smaller Reg·load value have a higher ability to maintain VOUT regulation despite changes to IOUT.
Dropout voltage VDO Also called the input-output voltage differential, the dropout voltage (VDO) is a difference between input and output voltages necessary to maintain output voltage regulation.
Current limit ICL ICL is the specified current value at which an LDO regulator begins limiting excessive output current in the event of overcurrent protection being tripped.
Undervoltage lockout threshold voltage VUVLO VUVLO is the input voltage of an LDO regulator at which its undervoltage lockout (UVLO) function is tripped. 
Temperature coefficient TCVO TCVO is a rate of change of the output voltage with respect to a change of 1°C in ambient temperature under the test conditions specified in a datasheet. LDO regulators with a smaller temperature coefficient value have a higher ability to maintain output voltage regulation despite changes in temperature.
Output noise voltage VNO VNO is the magnitude of noise that occurs at the output of an LDO regulator.
Ripple rejection ratio

R.R. (VIN)

R.R. (VBIAS)

 The ripple rejection ratio is the ability of an LDO regulator to suppress ripple in the input or bias voltage. It is expressed in dB. LDO regulators with a higher R.R. value have a higher ability to suppress ripple. Use R.R. as a guide when selecting LDO regulators for power supplies for sensor, analog, and other highly noise-sensitive circuits. The ripple rejection ratio is also called the power supply rejection ratio (PSRR) or the supply voltage rejection ratio (SVRR).
Load transient response ΔVOUT The load transient response (ΔVOUT) is an amount of change in the undershoot and overshoot of the output voltage for a load current step change. LDO regulators with a large ΔVOUT value might affect the correct operation of a system.
Output discharge on-resistance RSD RSD is the on-resistance of the internal N-channel MOSFET connected between the VOUT and GND pins of an LDO regulator.
Thermal shutdown temperature TSD TSD is the junction temperature at which thermal shutdown is tripped in the event of excessive power dissipation or an excessive increase in ambient temperature.
Thermal shutdown temperature hysteresis TSDH TSDH is a difference between the temperature at which the LDO regulator trips thermal shutdown and the temperature at which it recovers from thermal shutdown.

The following application note also provides the definitions of the terms for LDO regulators:

Application note: LDO Regulators: Glossary

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