TPS92200D1EVM: TPS92200D1EVM

Kiran Ajjevadimath

Part Number: TPS92200D1EVM

Tool/software:

HI,

We are using TPS92200D1EVM, and below are our questions:

1) We see EVB is configured for 495mA current by having Rsense of 0.2 ohm. I currently have 20-ohm load and current is increasing linearly with input voltage of EVM instead of constant 495mA. Is this expected?

2) We have another constant current source connected in parallel to EVB output and the output current of constant current source is 100mA. With this configuration i expected 600mA at load (20 ohm), considering 500mA from EVB and 100mA from CCS. But the EVB output current itself if adjusted, i mean output current is reduced from EVB (400mA instead of 500mA), resulting in total current at load to 500mA.

Let me know for more details.

Thanks,

Kiran. A

2 months ago

0 Gui He 2 months ago

TI__Mastermind 28406 points

Hi Kiran

(1)What's the Vin voltage you applied and did you set current limit?

(2)The total current flow through the current sample resistor. The total current is regulated as 0.5A, so the current from EVM is reduced to 0.4A.

Thanks and best regards.

0 Kiran Ajjevadimath 2 months ago in reply to Gui He

Prodigy 140 points

Hi Gui He,

1) We haven't made any changes on EVB, the rsense is 0.2ohm on board. I have load of 20ohms at output, and i tried with Vin-12V (current was ~550mA) || Vin- 15V (Current was 705mA) || Vin -18V (Current was 813mA). While i expected load current to be constant over input voltage change.

2) So, it means, the R4 measures the current and regulates it to 500mA at load so output of LED driver is reduced.

0 Gui He 2 months ago in reply to Kiran Ajjevadimath

TI__Mastermind 28406 points

Hi Kiran

Yes the output current should be constant over Vin; how did you measure the current? Did you measure voltage of FB? VFB should be constant as 0.1V.

The led driver regulate the VFB=VREF, and total Iout=VFB/Rsense (Rsense=0.2Ω, Vref=0.1V); the total Iout is the current that flow through Rsense(R3+R2).

Can you please share what's your End equipment?

Thanks and best regards.

0 Kiran Ajjevadimath 2 months ago in reply to Gui He

Prodigy 140 points

Hi,

I have connected a resistive load of 20 ohm at the output of LED driver. I measured current at both load and source end; the current is linearly increasing with VIN.

I haven't measured VFB on Eval board.

My current expectation is, with varying input voltage and load, the output current shall be fixed at 495mA(considering 0.2 Rsense), which is not happening.

Thanks,

Kiran. A

0 Gui He 2 months ago in reply to Kiran Ajjevadimath

TI__Mastermind 28406 points

Hi Kiran

with varying input voltage and load, the output current shall be fixed at 495mA(considering 0.2 Rsense)---Yes that should be expected.

Can you please share some of the waveforms? like the Vin, VFB, SW?

Thanks and best regards.

0 Kiran Ajjevadimath 1 month ago in reply to Gui He

Prodigy 140 points

Hi,

Plese find below waveforms:

VIN (Blue) vs SW(Yellow):

VIN(Blue) vs FB(Yellow):

0 Gui He 1 month ago in reply to Kiran Ajjevadimath

TI__Mastermind 28406 points

Hi Kiran

The schematic is as below, right?

What signal did you apply to TP7(DIM)? Seen from the waveform, the PWM dimming is applied and dimming frequency is 200Hz. Can you please share the waveform?

Thanks and best regards.