Post Date : Nov 28, 2023 / Last updated : Jan 15, 2024

The output type of voltage detector has two types; Nch open drain type and CMOS type.

Nch open drain output
Nch open drain output: output voltage
CMOS output
CMOS output: output voltage

Nch open drain output

For Nch open drain output, Nch FET is inserted only in between output terminal and GND terminal.
As FET is inserted on GND side only, it is necessary to prepare pull-up resistance and pull-up voltage externally. The level conversion of output voltage according to a device at output destination is available by preparing pull-up voltage according to microcomputer etc. at output destination.

CMOS output

For CMOS output, CMOS inverter is mounted in the output terminal.
Unlike Nch open drain output, it is not necessary to prepare pull-up resistance or pull-up voltage.
For this reason, CMOS output has no supply current flowing into pull-up resistance, so it is optimum for low power applications.

■How to select an Output Type

Here explains proper use of Nch open drain and CMOS.

When Nch open drain is necessary

If the input voltage of voltage detector is different from the voltage required by a device on output side, it is necessary to use Nch open drain output.
Nch open drain pulls up the output with resistance. If output voltage becomes "L", the current flows via pull-up resistance. For this reason, for a device in which low power is important, it is necessary to pay attention to the current flowing into the pull-up resistance.

When CMOS output is necessary

COMS output can be used when the input voltage of voltage detector is same as "H" voltage of MCU. As a concrete example, there is a device whose MCU is directly connected to a battery.

Unlike Nch open drain, supply current does not flow via pull-up resistance when output is "L", so CMOS output is optimum for applications that emphasize low quiescent current.