SLVAFE6 December 2022 TPS62870 , TPS62870-Q1 , TPS62871 , TPS62871-Q1 , TPS62872 , TPS62872-Q1 , TPS62873 , TPS62873-Q1 , TPS62874-Q1 , TPS62875-Q1 , TPS62876-Q1 , TPS62877-Q1 , TPS6287B10 , TPS6287B25 , TPSM8287A06 , TPSM8287A10 , TPSM8287A12 , TPSM8287A15 , TPSM8287B30
Fixed output voltage converters like TPS6287x generate an accurate output voltage with tight tolerance and temperature drift. This is hardly achievable with a DC-DC converter having an adjustable output voltage which is set by a resistor divider. The tolerance of the resistors of the feedback divider and the temperature drift of the resistors significantly affect the accuracy. At converters having a fixed output voltage the output voltage usually cannot be changed unless a digital interface is available and supports that. This is possible with devices of the TPS6287x family if the interface can be used to adjust the voltage if needed. If no interface is available at the time the change is needed there is a possible workaround which is described in this application note in detail.
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At converters having a fixed output voltage, the output voltage usually cannot be configured in a simple way. Devices of the TPS6287x family support selecting a predefined output voltage using an appropriate configuration at the VSEL pin. If the desired output voltage cannot be selected using VSEL, the output voltage still can be programmed using the digital interface once the device is powered properly. This change can be done before the device is enabled. After enable, the device starts into the newly programmed output voltage. Additional details can be found in the TPS6287x-Q1 2.7-V to 6-V Input, 6-A, 9-A, 12-A, 15-A, Automotive, Stackable, Synchronous Step-Down Converters with Fast Transient Response data sheet.
If this process cannot be done, for example, if there is no interface communication possible since the host for the interface is not active before or during startup, other means of addressing that are required. This application note explains how this problem can be addressed using a resistor divider. This application note also explains the limitations of this approach.