The PCA9561 is a 20-pin CMOS device consisting of four 6-bit non-volatile EEPROM
registers, six hardware pin inputs and a 6-bit multiplexed output. It is used for DIP
switch-free or jumper-less system configuration and supports Mobile and Desktop VID
Configuration, where five preset values (four sets of internal non-volatile registers and
one set of external hardware pins) set processor voltage for operation in various
performance or battery conservation sleep modes. The PCA9561 is also useful in server
and telecommunications/networking applications when used to replace DIP switches or
jumpers, since the settings can be easily changed via I2C-bus/SMBus without having to
power down the equipment to open the cabinet. The non-volatile memory retains the most
current setting selected before the power is turned off.
The PCA9561 typically resides between the CPU and Voltage Regulator Module (VRM)
when used for CPU VID (Voltage IDentification code) configuration. It is used to bypass
the CPU-defined VID values and provide a different set of VID values to the VRM, if an
increase in the CPU voltage is desired. An increase in CPU voltage combined with an
increase in CPU frequency leads to a performance boost of up to 7.5 %. Lower CPU
voltage reduces power consumption. The main advantage of the PCA9561 over older
devices, such as the PCA9559 or PCA9560, is that it contains four internal non-volatile
EEPROM registers instead of just one or two, allowing five independent settings which
allows a more accurate CPU voltage tuning depending on specific applications.
The PCA9561 has two address pins, allowing up to four devices to be placed on the same
I2C-bus or SMBus.