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.
| 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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