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Application Note : LDO Regulators (Linear Regulators)

LDO Regulators with ECO Function

An ECO Function is a function which implements a High-performance Type LDO Regulator and a Low Supply Current Type LDO Regulator integrated in a single chip.
Having this ECO function enables a performance of three operating modes instead of only two; On mode, Off mode, and Sleep mode.

The LDO regulator with ECO function is able to switch between a fast response mode (high-performance) and a low power mode (low supply current), additionally it can be switched to the Off mode by the CE pin.
The LDO regulator with ECO function is able to reduce the supply current and number of parts on the board space since it switches between those modes depending on the device status.

Comparison of Supply Current

Comparison of Supply Current

The examples of the supply current of a Low Supply Current Type LDO Regulator, a LDO Regulator with ECO Function, and a High-performance Type LDO Regulator are shown in below table.

Low Supply Current Type ECO Function Included High-performance Type
RP110 RP201 RP112
Typ. 1 µA Low Power Mode: Typ. 1.5 µA
Fast Response Mode: Typ. 55 µA
Typ. 75 µA

Comparison of Ripple Rejection Ratio

The ripple rejection ratio graph of a Low Supply Current Type LDO Regulator, a LDO Regulator with ECO Function and High-performance Type LDO Regulator. (Since the measurement conditions may be slightly different, please consider below graphs as a reference.)

RP110x25xx

Low Supply Current Type

RP201x28xx

ECO Function Included

RP112x28xx

High-performance Type

Comparison of Load Transient Response

The load transient response graph of a Low Supply Current Type LDO Regulator, a LDO Regulator with ECO Function and High-performance Type LDO Regulator. (Since the measurement conditions may be slightly different, please consider below graphs as a reference)

Please note that the scale of the horizontal-axis for Low Supply Current Type and a Low Power Mode are in "ms", while those of a High-performance Type and a Fast Response Mode are in "µs", the load transient response is more than 100 times faster and output voltage variations are suppressed to 1/10.

RP110x25xx

Low Supply Current Type

R1162x28x (ECO=L)

ECO Function Included
Low Power Mode

R1162x28x (ECO=H)

ECO Function Included
Fast Response Mode

RP112x28xx

High-performance Type

How to Switch the ECO Function

There are four methods of switching the ECO Function, and Ricoh offers four types of products utilizing each method.

[1] Manual Mode Shift Type (with ECO pin)

The mode is switched by controlling H/L to the ECO pin.

Manual Mode Shift Type (with ECO pin)

[2] Automatic Mode Shift Type

Switching occurs between low power mode and fast response mode depending on system load (output current).
The switching point is fixed in the IC.

Automatic Mode Shift Type

[3] Seamless Type

Instead of switching between two modes, a transition is made between modes depending on the output current.
The supply current smoothly decreases as the system load (output current) decreases.

Seamless Type

[4] Manual/Automatic Mode Shift Type

Fast response mode and Automatic mode shift can be switched by controlling H/L to the AE pin.
When AE="H", the mode is set to the fast response mode, and when AE = "L", the LDO regulator operates like the Automatic Mode Shift Type.
This type has both advantage of the Manual Mode Shift Type and the Automatic Mode Shift Type.

Manual/Automatic Mode Shift Type

Fast response mode and Automatic mode shift

ECO Function Included

Manual Mode Shift Type

Automatic Mode Shift Type

Seamless Type

Manual/Automatic Mode Shift Type

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