LP8860-Q1: The questions about LP8860-Q1

Hi Tiper,

Regarding your questions:

1. You could but this is not recommended. The output voltage would stay at a minimum 16V, so it'll be highly inefficient since you'll be consuming extra power by having output voltage much higher than necessary. Also, even if output voltage is lowest 16V, boost components should be rated for 48V max output voltage in case an open string fault occurs. 

2. Do you require special features of LP8860 in your application (i.e. Phase Shift, Hybrid Dimming, Register Brightness Control)? If not, you could use TPS61194-Q1 or LP8861-Q1 (+ Power Line FET protection) devices which are much simpler. These devices have 4 channels up to 100mA/string, which should be enough for your application (540mA/9 = 60mA/string). Also, this family of devices have integrated FET which lowers system cost.

3. There are customers that cannot re-program EEPROM for production so we want to offer various options.

4. You'll need to request access to LP8860-Q1 tools/software first. You can do so from LP8860-Q1 product page by clicking on Request Now:

If you have already done so, you should be able to access LP8860 files/tools by going to myTI -> My activity -> mySecure software.

Best Regards,

Salome

Hi, Salome:

Many thanks for your detail explanation.

I chekced your advices( LP8861-Q1 and TPS61194-Q1). these two parts support only up to 400mA current( all channels are parallel) ;

For my application( Vin= 5V; the LED is 3S9P and they are common Anode and common Cathode fixed in panel; the total current is 540mA; PWM dimming is OK);

Do you have any recomendation?

Thanks again.

Tiper Liu

Hi Tiper,

I understand now. Previously I thought that the parallel strings needed to be independent but from your application details, it seems like a device such as the TPS61500 would be a better solution.
With the TPS61500 you can set the LED output current through an external resistor so for your case 540mA. Only thing to check would be that the application doesn't exceed the 3A boost current limit, which with your conditions it shouldn't.

Does the application require Automotive Qualification? If so, I'll need to check another solution. If not, I think TPS61500 would be the best recommendation.

Best,

Salome

Hi, Salome:

We need Automotive grade part, sorry for I don't provide the detail application requriements in above content. Do you have other recomendation. Thanks again.

Best Regards

Tiper Liu.

Hi Tiper,

Sorry, currently TPS61165-Q1 would be the closest to TPS61500 device that is automotive graded, but it has peak switch current limit of 1.2A (max 400mA LED string current), which wouldn't be enough for your application conditions .

Best Regards,

Salome