Circuit Review: Multi-function Radiosonde Design

[hyunsu5203]

I have designed this circuit for a multi-function radiosonde system. The circuit diagrams are attached below.

I'm experiencing a voltage fluctuation issue: when the heater is turned on/off, the voltage changes by approximately 0.4V~0.5V. Additionally, I'm not entirely sure if the PMOS and NMOS configurations are correct.

I would greatly appreciate any feedback or suggestions regarding these issues, potential improvements, missing components, or design issues you may notice. Thank you for your time and expertise.

[Andy Chee]

Your voltage fluctuation issue may be related to PCB design, not schematic.

Please attach your PCB design.

[hyunsu5203]

Thank you for your reply.
I haven’t designed the PCB layout yet. So far I have only tested the circuit in PSPICE.
The heater load is about 1.5 A, and the power source is modeled as four 18650 cells in parallel.
When the heater is switched on and off, the simulated output voltage shows about 0.4–0.5 V of overshoot/undershoot.

The first image shows my PSPICE schematic of the 1‑cell (3.7 V) to 5 V boost converter.

The second image shows the general transient response of the circuit.

The third image shows a zoomed‑in view of Vout and Iout during the load transient (heater on/off).

Do you think this amount of voltage fluctuation is acceptable for this kind of boost converter on a real PCB, or does it suggest that my circuit design or component selection should be improved (for example, by choosing a different output capacitor, inductor, or compensation)?

Any advice or suggestions on how to improve the transient response or overall robustness of the converter would be greatly appreciated.

[Andy Chee]

My advice is to power the heater directly from the battery, not with a boost converter.

[hyunsu5203]

Thank you for your advice, I will reflect it and change the design.