The performance of any switching regulator depends as much on the layout of the PCB as the component selection. Following a few simple guidelines maximizes noise rejection and minimizes the generation of EMI within the circuit.
Discontinuous currents are the most likely to generate EMI, therefore care should be taken when routing the following paths. The main path for discontinuous current in the TPS9260xy-Q1 buck regulator contains the input capacitor (CIN1), the recirculating diode (D1), the N-channel MOSFET (Q1), and the sense resistor (RLIM1). In the TPS9260xy-Q1 boost regulator, the discontinuous current flows through the output capacitor (CO1), D1, Q1, and RLIM1. In the buck-boost regulator, both loops are discontinuous and require careful attention to layout. Keep these loops as small as possible and the connections between all the components short and thick to minimize parasitic inductance. In particular, make the switch node (where L1, D1 and Q1 connect) just large enough to connect the components. To minimize excessive heating, place large copper pours adjacent to the short current path of the switch node.
The RT, COMP, ISNS, ICTRL, OVFB, ISP, and ISN pins are all high-impedance inputs which couple external noise easily; therefore, minimize the loops containing these nodes whenever possible. In some applications, the LED or LED array can be far away (several inches or more) from the TPS9260xy-Q1 family of devices, or on a separate PCB connected by a wiring harness. When using an output capacitor where the LED array is large or separated from the rest of the regulator, place the output capacitor close to the LEDs to reduce the effects of parasitic inductance on the ac impedance of the capacitor.
AGND and PGND must be separated and connected at the input GND connector.
The TPS9260xy-Q1 family of devices has two independent channels. in order to avoid crosstalk, the POWER GND of CH1 and CH2 must be separated and connected at the input GND connector.