Automotive 12V smart low-side switch HITFET™ BTF3125EJ application circuit with configurable R-L-C load

Open online SPICE simulator circuit link: atv_bp_12V_low_side_BTF3125EJ_application_circuit.tsc

Automotive Smart Low-Side Power Switch BTF3125EJ
Application circuit: PWM Input Signal

The BTF3125EJ is a 125 mΩ single channel Smart Low-Side Power Switch providing embedded
protective functions. Infineon’s HITFET™ protected low-side switches drive resistive, capacitive as
well as inductive loads. The BTF3125EJ is automotive qualified and is optimized for 12V automotive
and industrial applications.

The model of the bulb has the thermal behavior of the intrinsic resistance inside and comply with the
actual bulb cold/hot resistance of a real bulb. When the bulb is cold, the inrush current is quite big
(hence the Over Current trigger and current limitation protection) and when it heats up, the resistance
increases so the current decreases to nominal value.

The self-heating of the device has been deactivated (THERMAL_MODEL=0) so that the behavior of the
bulb can be observed.

{=== Thermal Model Description BTF3125EJ ===}

THERMAL_MODEL=0: self heating deactivated
THERMAL_MODEL=1: P=1W; T=85°C; PCB type: 1s0p 300mm2
THERMAL_MODEL=2: P=1W; T=85°C; PCB type: 1s0p 600mm2
THERMAL_MODEL=3: P=1W; T=85°C; PCB type: 1s0p footprint
THERMAL_MODEL=4: P=1W; T=85°C; PCB type: 2s2p with thermal via
where: P=power on the power transistor; T=ambient temperature

change simulation time:
"Analysis->Transient: Start - End Display"

{=== How to select a Load ===}

LOAD_TYPE:= 1 {Lamp 5W }
LOAD_TYPE:= 2 {Lamp 10W}
LOAD_TYPE:= 4 {Lamp 21W}
LOAD_TYPE:= 8 {Lamp 27W}
LOAD_TYPE= 16 {Resistive Load}
LOAD_TYPE:= 32 {Inductive Load}

{=== How to change SPICE convergence parameters ===}

Change the convergence-speed-accuracy trade-off with "Analysis -> Analysis Parameters..."
1) How to improve Accuracy
To speed up the simulation, the TR maximum time step [s] can be adjusted (default value = 10Gs).
- high values may produce less accuracy during signal transition
- a general rule is to have the ratio between test duration (End display) and TR maximum time step
in the range of 1k to 10k
2) How to improve Convergence
The SPICE model is not guaranteed to converge in every test situation with the default simulator settings.
Increasing gradually the following analysis parameters may help achieving the convergence:
Important: exceeding indicated values may impact results accuracy.
- DC absolute current error [A] from 1n (default) to 10n
- DC absolute voltage error [V] from 1u (default) to 10u
- DC relative error [%] from 1m (default) to 10m