2 BOM Modifications Required

The following steps must be taken to ensure proper operation of a 3-channel buck converter on a populated 4-channel EVM (TPS7H4001QEVM-CVAL). An overview of where changes are required is shown in Figure 2 while a summary of all changes is provided in Table 1.

Figure 2. Overview Of Required Modifications

1. Modifications near MASTER DUT U1 (Figure 3 and Figure 7)
   1. Isolate VSENSE feedback pin 32 of SLAVE1 by removing 0-ohm jumper R20.
   2. Isolate SYNC2 pin 6 of SLAVE1 device by removing 0-ohm jumper R13.
   3. Replace compensation circuit at R7, C14, C15 near DUT U1:
      1. R7=3.0kohms
      2. C15=27nF
      3. C14=240pF
Figure 3. Modifications near MASTER DUT U1
2. Modifications near SLAVE1 DUT U2 (Figure 4 and Figure 8)
   1. Isolate VIN pin 4 of Slave 1 DUT U2 by removing 0-ohm jumper R30
   2. Remove input capacitors of Slave 1 DUT U2 by completely removing, or lifting one terminal of each capacitor as shown in Figure 5. (C35, C36, C38, C39, C40, C41, C42, C43)
   3. Remove output capacitors of Slave 1 DUT U2 by completely removing, or lifting one terminal of each capacitor so as to remove from circuit as shown in Figure 5. (C52, C53, C54, C55, C56, C57, C58, C60)
   4. Using a solder iron and tweezers, carefully lift the following pins off the PCB as shown in Figure 6 (note only pins 31 and 33 are shown in graphic)
      1. Enable pin (EN pin2)
      2. Soft start pin (SS/TR pin31)
      3. COMP pin (COMP pin 33)
Figure 4. Modifications near SLAVE1 DUT U2
Figure 5. Open Circuit Input/Output Capacitors
Figure 6. Lift Pins 2, 31, 33 from PCB