SLAU320AJ July 2010 – May 2021
From the input voltage of 8 V to 10 V dc, onboard voltages are generated using adjustable LDOs: U3 generates VCC of 3.0 V as the supply voltage for the host controller MSP430F5437, U4 generates VCC of 2.1 V to 3.6 V as the supply voltage to the target device, and U1 generates VPP of 6.7 V to program the JTAG access fuse. While the fuse is being programmed, a peak current of 100 mA can flow through the TEST or TDI input pin (see the corresponding target MSP430 device data sheet).
When using a target system that is powered locally, the VCClevel from the target device should be connected to pin 2 of the JTAG connector that supplies the I/O voltage translator in the REP430F. This ensures that the I/O levels of the REP430F match the I/O levels of the target device. The programmable LDO that can supply the target device should be disabled when the target device is powered locally. When pin 2 of the JTAG connector from REP430F is not connected to the target VCC, a difference between the I/O voltage rails of the target device and the REP430F can occur and communication between host and target may fail due to invalid logic levels. It is also possible under these conditions that device damage can occur.