Skip to main content
Knowledgebase
Home
Renesas Electronics Europe - Knowledgebase

Terminology

Latest Updated:11/01/2005

Question:

Terminology

Answer:

Output voltage
This is the most important characteristic of a 3-terminal regulator. The upper-limit and lower-limit values of the output voltage (i.e., accuracy of the output voltage) are specified under given conditions of junction temperature, input voltage, and output current (load current) .
When designing your system using a 3-terminal regulator, make sure that the conditions of the output voltage of the regulator are satisfied. The output voltage of Renesas Electronics' 3-terminal regulators is indicated in their part name.
Example uPC2405AHF: uPC2400AHF Series with output voltage of 5 V
Reference:Usage of Three-Terminal Regulators

 

Line regulation
This is the maximum value of changes in the output voltage when the input voltage varies in a specific range at constant conditions of junction temperature (normally Tj=125°C) and output current. The lower the Line regulation, the higher the stability of the output voltage of an IC.
Reference: Usage of Three-Terminal Regulators

 

load regulation (output stability)
This is the maximum value of changes in the output voltage when the output current (load current) varies in a specific range at constant conditions of junction temperature (normally Tj=125°C) and input current. The lower the load regulation, the higher the stability of the output voltage of an IC.
Reference: Usage of Three-Terminal Regulators

 

Quiescent current
This is the current necessary for an IC to operate, which is specified as a current flowing from an input pin to a GND pin.

 

Ripple rejection
This is the ratio expressed in dB at which the alternate current (AC) component included in an input voltage attenuates before it is produced as an output voltage. The higher the ripple rejection, the better the performance as changes in the input voltage do not appear as the output voltage.

Ripple rejection =20log (ΔVIN/ΔVO) [dB]

The ripple rejection is dependent on the frequency of the AC component. Renesas Electronics usually specifies the ripple rejection of its products at 120 Hz.

 

Output noise voltage
When an IC operates, noise is internally generated. The output noise voltage is noise generated inside an IC and appears as an output and is expressed as an effective value. The lower the output noise voltage, the more suitable the IC is for the voltage for a circuit that handles audio signals or minute voltages.

 

Dropout voltage
This is the difference between the input voltage and output voltage required for an IC to produce a stable output voltage. The product of the input and output voltage difference and the output current is the input-output loss of the 3-terminal regulator. Therefore, the lower this value is, the lower the loss of the 3-terminal regulator.
Reference: Usage of Three-Terminal Regulators

 

Total loss
The total loss of a 3-terminal regulator is the sum of the input-output loss and the circuit loss.
In other words, total loss Pd can be expressed by the following equation.
Pd= (VIN-VO) ·IO+VIN·(Ibias+ΔIbias1)
(VIN-VO) : Input-output voltage difference
IO: Output current
Ibias: Quiescent current
ΔIbias1: Quiescent current change


Peak output current
A 3-terminal regulator has an internal overcurrent restriction circuit. The peak output current is an output current value at which the overcurrent restriction circuit starts operating. If an attempt is made to flow a current exceeding the peak output current, the output voltage drops.
Usually, the overcurrent restriction circuit is used in combination with a stable operation area restriction circuit, and the overcurrent is restricted at the lower peak output current if the voltage difference between the input and output is great (if the input voltage is high) or if the chip temperature is high. Take the uPC2900 Series with an output current of 1 A, for example. If the input voltage is high or if the chip temperature is high, the restriction circuits may operate, lowering the output voltage, even when the output current is less than 1 A.
Reference: Usage of Three-Terminal Regulators


Short circuit current
This is the current output from the output pin if the output short-circuited with ground by accident. This value is determined by the characteristics of the overcurrent restriction circuit. That is, the higher the input voltage and the higher the chip temperature, the more the current is restricted.

Caution This parameter does not guarantee the reliability. Do not short-circuit the output continuously. If continuous output short-circuiting must be guaranteed, use external circuits.

 

Temperature coefficient of output voltage
The output voltage changes depending on the chip temperature. The temperature change of output voltage is a change in the output voltage when the chip temperature is in a range of 0 to 125°C. The lower this value, the better. However, because this parameter is not a guaranteed value, it usually cannot be used for an application where changes in the output voltage with temperature are required. For applications where changes in the output voltage with temperature must be guaranteed, the following products are recommended.

uPC1093: Variable output shunt regulator
uPC1943, 1944, 1945: Low-voltage shunt regulator

 

Startup quiescent current
Low dropout regulators like the uPC2400 Series use a PNP transistor in their output stage. When the input voltage is low, therefore, this transistor saturates and a high current flows from the input to GND. At startup operation, the circuit operating current is at the maximum value of this current. Unless a current exceeding this value flows, the regulator does not operate correctly.

 

Fold-back type drooping (fold-back type load) characteristics
These are the changes in the output voltage expressed as load characteristics when the output current is gradually increased. The output current immediately before the output current decreases because the internal overcurrent restriction circuit of the IC operates is called a peak output current (IOpeak) . The output current at which the output voltage is decreased to 0 V by action of the overcurrent restriction circuit is called an output short-circuit current (IOshort).
If the peak output current is higher than the output short-circuit current, the output voltage vs. output current characteristic has a fold-back shape. If the peak output current is equal to the output short-circuit current, the characteristic curve shows "constant current drooping characteristics" in a shape like reversed letter "L".

Suitable Products
3 Terminal Regulators