TPS544C20: CNTL pin and PMBus operation

Hi Sakai-san,

To answer these questions, let us first consider the default value for the ON_OFF_CONFIG command.  In order to determine the default value for this command, and translate the value's meaning we will need to look in section 8.6 Register Maps, of the TPS544B20/C20 datasheet.

Section 8.6.2 ON_OFF_CONFIG (02h), specifies that the default command is 0x16, here is a breakdown of the bits of interest:

• 8.6.2.1 pu [4], default 1 = Device does not power up until commanded by the CNTL pin and OPERATION command as programmed in bits [2:0] of the ON_OFF_CONFIG register.
• 8.6.2.2 cmd [3], default 0 = Device ignores the “on” bit in the OPERATION command. This means the turn ON/OFF of these devices is by default controlled only by the CNTL pin.
• 8.6.2.3 cpr [2], default 1 = Device requires the CNTL pin to be asserted to start the unit.
• 8.6.2.4 pol [1], default 1 = CNTL pin is active high. This means that a voltage applied to the CNTL pin that is interpreted as logic HIGH will turn the device ON.

An even quicker method to determining default behavior, is by looking in section 8.5.1 Supported PMBus Commands of the datasheet.  Here we see that the default behavior for ON_OFF_CONFIG is: CNTL only. Active High.  Meaning that turn ON/OFF is controlled by setting the CNTL pin HIGH/LOW respectively, regardless of the OPERATION command setting.  This section is a good as a quick reference, but does not detail command functionality like the Register Maps section.

So to answer your questions:

· Can the TPS544C20 / TPS544B20 turn ON / OFF the power only by controlling the CNTL pin? Yes, by default this is how the device is configured.

· Is it necessary to set in advance via PMBus with TPS544C20 / TPS544B20? If yes, please tell me which address setting is necessary. If your intent is to control the device via the CNTL signal only, using a device with default values, then no.  For reference, the address of the commands of interest are 01h (OPERATION), and 02h (ON_OFF_CONFIG).

· If the value is saved in the built-in EEPROM after executing the above setting, is it possible to turn ON / OFF by controlling the CNTL pin only after the next startup? Based on your previous questions it seems that the default settings will fit this application and changes to these commands are not necessary.

Another section that may be of interest, is section 8.4.4 Operation with CNTL Signal Control of the datasheet.  This section highlights the CNTL active high/low voltages.

Thanks,