12V Automotive LED Driver IC LITIX™ Power Flex TLD5542-1QV - test bench Soft Start, Analog & Digital Dimming

Open online SPICE simulator circuit link: atv_lighting_TLD5542-1QV_testbench_SoftStart_OCL_PWM.TSC

Model Parameters:

Soft Start, Analog and Digital Dimming - Transient with TLD5542-1QV

- Double click on the green window to enter design criteria
- Click on "Run" and Simulate Transient

- frequency: specify directly the controller frequency [200kHz to 700kHz]
MFS feature related parameters (to disable the feature for other test-benches, make t_SOMFS longer than total simulation time)
- LED_initial: number of LEDs before performing the jump; this number must be the same with the number of LEDs connected
at the output; the range is between 2 and 16
- LED_after: number of LEDs after the jump; this number must be the same with the number of LEDs that will remain connect
at the output; the range is between 1 and 15
- t_PREP: time until Ccomp is discharged; give the compensation capacitors enough time to discharge, otherwise spikes will still
appear at the output
- t_SOMFS: time when MFS routine will start; for other test benches, keep this parameter higher than simulation time to deactivate
the feature

This test bench shows Soft Start, output current control via analog dimming and digital dimming via PWMI pin features.
SOFT_START and COMP capacitor values are chosen in order to see the impact of SOFT_START in the start-up until
the circuit is reaching steady-state. If COMP ramp is faster than SOFT_START ramp and exceeds SOFT_START
by more than 0.7V, then COMP ramp will be limited by SOFT_START. RFB is set to 150m in order to have 1A at the output.
SET pin is decreased from 1.4V (100% analog dimming) to 0.8V (50% analog dimming). When PWMI is in logic low,
the output current will go to 0A and the output capacitor is starting to discharge (digital dimming).

Notes:
BODY_DIODE is not a real diode but a Voltage Controlled Current Source which models the threshold and ON/OFF
states resistance. RCOMP is a placeholder for further adjustment of the resistor for stability purpose. Keep unchanged
otherwise. S2G is a virtual pin used for monitoring short to ground fault if VFB<0.563V for at least 8 clock cycles.
During start-up, the detection is ignored until VSOFT_START>1.75V.