I would like to run 4 phases with a switching frequency of 250KHz. How are the RT and SYNC pins to be connected on all 4 devices?
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Hello Daniel, figure 8-6 shows a configuration for 500KHz operation since the first device's RT pin is open. If I want to operate at 250KHz, can I connect RT pin of first device to a value that sets operation at 250KHz also? i.e., can I connect RT pin of ALL devices to the value for 250KHz and connect SYNC as shown in the Fig 8-6? If you look at Table 1, for "Primary Mode", it says to leave RT pin floating which seems to imply you can only operate at 500KHz. If I want to operate at any other frequency, it seems like I could only do this by using external sync, is this correct? What I would like to do, if possible, is to use the RT pin of first device to set to 250KHz and have the other 3 devices sync to this first device.
In order to use the RT pin of the TPS7H4001 as a clock output for device synchronization, the RT pin must be left floating. This necessarily means that the only switching frequency that can be used with this mode is 500kHz. When a device has an RT resistor populated to set the switching frequency, SYNC1 and SYNC2 become inputs, therefore making the only option 500kHz when RT is floating.
However, when using external synchronization mode, any frequency between 100kHz and 1MHz can be used.
Section 188.8.131.52 of the device data sheet goes into more detail about external synchronization mode.