Tool/software:
Hello,
I’m working with the TPS63900 boost converter to charge a 5 F supercapacitor from a 3.6 V input rail up to 4.7 V. The device successfully charges the supercap, but once it reaches the target voltage, the average current draw of the system rises by about 200 µA compared to the no‐load condition.
- Input voltage: 3.6 V
- Output voltage: 4.7 V
- Current is limited to 2.5mA
- Input capacitor: 10uF+10uF
- Output capacitor: 22uF
- Output supercapacitor: 5F (ESR_MAX=0.16 ohms, DCL=30uA, RatedVoltage=5.4V)
- Inductor: DFE252010F-2R2M=P2
Behavior at 4.7 V threshold (Photo 1):
I first pre‑charged the supercap externally to 4.85 V so that the TPS63900 remains in shutdown (quiescent current ≈ 0 µA). In this state, my system draws a steady ≈ 700 µA. As soon as the capacitor’s voltage drifts just below the 4.7 V setpoint, the converter “wakes up” with current limited to 2.5mA and the total current jumps by roughly another 200 µA. Is this wake‑up overhead expected? What internal leakage or control‑loop activity causes that extra draw once VOUT falls under the programmed threshold? The measured output current from the converter is 35uA.
Behavior during 3 V startup (Photo 2):
In a separate test I configured VOUT to 3 V and observed very large current spikes at startup before the converter settled into the 2.5 mA limit. These spikes were on the order of several milliamps and lasted for a few milliseconds. Could ambient factors such as temperature or humidity meaningfully influence these dynamic startup spikes or the converter’s regulation behavior when operating at different output settings?
Finally, do you have any published efficiency vs. load or efficiency vs. current‑limit setting curves for the TPS63900 when operating at 4.7 V? Any insights into the ~200 µA wake‑up current, recommended efficiency data, or notes on environmental sensitivity would be greatly appreciated.
Thank you!
Marc Ledesma
