Other Parts Discussed in Thread: TINA-TI
Tool/software: WEBENCH® Design Tools
Hi,
I'm reviewing to use TPS61169 and found TINA-TI Reference Design & Spice Model (here).
As shown in the figure 1 (see below), the as-provided reference design seems to behave well. Since the value of Rset (which is R1 in TINA-TI Reference Design) was 10.1 ohm, output current (ILED) would be 20.198 mA (= 204 mV / 10.1 ohm).
<Figure 1. Simulated ILED from TPS61169 reference design with Rset = 10.1 ohm>
The problem is if I change the Rset value to 1.0 ohm as shown in figure 2, the expected output current (ILED) will be 204 mA (= 204 mV / 1 ohm). However, the simulated ILED is far lower than the expected value as shown in figure 3, where the ILED ~99 mA.
<Figure 2. Changed Rset (= R1) value to 1 ohm>
<Figure 3. Simulated ILED from TPS61169 reference design with Rset = 1 ohm>
Where the discrepancy comes from? I'm confused if this is just a simulation-related problem or if it will also happen to the real situation.
Please note that I set the transient time to 15 ms, which is longer than the soft start-up time (6.5 ms).
Please also note that I'd tried to increase the VIN to 5 V and only a slight increase of ILED (~ 135 mA) was observed, which was still lower than the expected value. I'd also tried to use TPS61169 PSpice Transient Model with OrCAD Capture, and I found the same results.
It would be extremely grateful for any comments for this issue.
Regards,
Seongjun
