I am prototyping a mobile radio device and using the TPS61260EVM-673 evaluation board. I am driving the TPS61260 with a single 1.55V Silver Oxide cell and using the TPS61260 to convert up to 3.3V (as the stock evaluation board does).
When I enable the TPS61260 to provide power to 6 discrete low power components, it works fine, bringing the voltage up to 3.3V as seen here. Blue is the TPS61260 output voltage, red is a generated clock and green is a pulse that will turn on a radio.
When I add in a DSC8101 oscillator chip programmed for 150MHz that is not yet enabled to the circuit (and will be enabled on the green pulses), the TPS61260 rises to 1.6 V and will not put out a higher voltage. Measuring the current into the DSC8101 shows 6 mA on the failed startup. The DSC8101 will use a maximum of 35 mA when enabled.
If I enable the TPS61260 first and then connect up the DSC8101, the TPS61260 reaches 3.3V and stays there and the oscillator puts out the 150 MHz pulses running fine as shown here.
So I am seeing TPS61260 startup issues similar to others I have seen in this forum and had a few questions:
1. Does the TPS61260EVM-673 evaluation board use an old version of the TPS61260 chip or one with the startup issues resolved (The board sticker says HPA673-001; TPS61260EVM-673)?
2. I will try moving my battery next to the TPS61260 to minimize resistance, but was concerned by this issue as I will be committing this to a circuit board shortly, but saw in the forums multiple unresolved startup issues. Any suggestions on avoiding this issue on the board layout, besides following your layout guide design?
3. When the radio is pulsing for 20 msec, once every 0.8 to 1.6 seconds, it draws 85 mA, causing the output voltage to drop. Adding 600 uF of ceramic capacitors lessens the voltage from to reaching 2.5V as seen in the following figure (Green is the TPS61260 output voltage, Blue is the oscillator enable pulse and red is the radio output signal). Will the TPS61260 have an even more difficult time with startup when the higher capacitance is added?
