Can the Schottky Barrier Diode (SBD) be omitted to reduce bill of materials (BOM) cost when designing a power management system using S6BP501A or S6BP502A?
No. When VOUT5 reaches the output setting voltage of 5 V, S6BP501A (or S6BP502A) turns off internal regulator REG between VIN-VB terminal and uses voltage from VOUT5 to maintain switching operation. REG will be turned off regardless of VIN voltage. Therefore, if SBD is omitted and VOUT5-VDD/VB connection is left open, VB and VDD voltages that control switching operation cannot be maintained; this stops the switching operation. Additionally, if SBD is omitted and VOUT5-VDD/VB connection is shorted, 5 V from REG will be applied to VOUT5V before DD5V starts switching. Consequently, DD5V detects overvoltage protection and switching operation will not start. Hence, make sure to use SBD in your design. Note that an SBD with low forward voltage (Vf) is necessary to avoid Under Voltage Lockout (UVLO) of VB.