Toshiba TCR15AG Series, Reference Manual

Page: 13 / 18

RD030-RGUIDE-02
2019-05-08
Rev.2
13 / 18
© 2019
Toshiba Electronic Devices & Storage Corporation
The output voltage (V
OUT
) is calculated as follow:
where, R1 and R2 are voltage divider resistor values. Suppose that R1=48k Ω and R2=24k Ω , which
are the recommended values for a V
OUT
of 1.8V.
The TCR15AGADJ provides the maximum output voltage when its internal reference voltage ( V
ADJ
)
is at the maximum (0.612V), R1 has the maximum value within the register’s specification, and R 2
has the minimum value within the register’s specification . If you select commonly used high-
accuracy resistors with 0.5% tolerance , then R1 is 48.24k Ω maximum, and R2 is 23.88kΩ minimum.
Substituting these values into the above equation, the maximum V
OUT
value is calculated to be
1.848V, which is 2.7% higher than the typical V
OUT
value of 1.8V.
On the other hand , the TCR15AGADJ provides the minimum output voltage when V
ADJ
is at the
minimum ( 0.588V ), R1 has the minimum value (47.76k Ω ), and R2 has the maximum value (24.12k
Ω ). So the minimum V
OUT
value is calculated to be 1.752V , which is 2.7% lower than the typical V
OUT
value of 1.8V.
Fixed-output LDO regulator
The TCR15AG18 has an output voltage accuracy of ±1%. As described before, the TCR15AGADJ
is ±2.7% even when resistors with 0.5% tolerance are used , while the fixed-output LDO regulator
provides an accuracy of ±1%. As shown by these examples, a fixed-output LDO regulator suits the
designing of a power supply when high-accuracy output voltage regulation is required.
In addition, compared with adjustable-output LDO regulators, fixed-output LDO regulators help
reduce the parts count and the board area since they do not require outside resisters of voltage
divider.
The typical output voltage and its accuracy are specified under the test conditions given in a
datasheet. It should be noted that the output voltage may drop if the output current is higher than
the actual applications.