MP3394S – Can LED channels be paralleled to drive a single LED string at higher current?

Lighting Solutions
1

Hello MPS Support Team,

I am considering using the MP3394S for an LED driving application in outdoor parking equipment, and I have a question about channel paralleling.

Background: Our distributor informed us that it is possible to combine multiple LED output channels (LED1–LED4) of the MP3394S to drive a single LED string at a higher current than the 200 mA per-channel maximum. However, I could not find any description or application circuit for this usage in the datasheet or on the MPS website.

Questions:

  1. Is it officially supported to connect multiple LEDx pins together to a single LED string in order to increase the total drive current (e.g., 2 channels paralleled for 400 mA, or 4 channels paralleled for 800 mA)?

  2. If this is supported, could you provide a recommended application circuit or any design guidelines? Specifically:

    • How should the ISET resistor be configured?

    • Are there any concerns with current balancing between channels?

    • Will the open/short LED protection function correctly in this configuration

Thank you for your support.

Best regards

2

Hi @Syuhei_Makino ,

You are correct that the datasheet does not specify if the channels can be connected in parallel or not for MP3394S. I know some of our devices, such as the MPQ3369 and MP3367, can support channels in parallel (application diagram showcases it).

I will ask my team for more details about the MP3394S. In the meantime, can you help providing the following:

  1. What is the input voltage?
  2. How much current do you desire to drive the LEDs?
  3. How do you intend to use the LED driver (how many separate LED strings, how many channels are paralleled, and how many LEDs per string)?
  4. What is the specific application for the LED driver (I know you mentioned parking equipment, but is it like a display, etc? What is the size of the display?)

Thanks,
Rubas

3

Hi Rubas,

Thank you for looking into this and for the reference to the MPQ3369.

I checked the MPQ3369 datasheet and confirmed that its Features
section explicitly states:
“Allow to Connect Multiple LEDx Pins for One LED String”

This is exactly the functionality I am asking about for the MP3394S
— connecting multiple LEDx output pins WITHIN A SINGLE IC to one
LED string to increase the total drive current.

Below are the application details you requested:

  1. INPUT VOLTAGE

  • 12V DC or 24V DC
    (The design can accommodate both voltages.)

==============================================

  1. LED CONFIGURATION

We plan to support multiple LCD backlight panels using the same
PCB with component mounting variations (stuffing options).
There are three LCD types:

[LCD Type 1] — Standard 4-string configuration

  • LEDs per string : 8 in series
  • Vf per string : 24V – 27V
  • Number of strings: 4 (one per channel: LED1, LED2, LED3, LED4)
  • Current per string: 100 mA
  • Total current : 400 mA
  • No channel paralleling needed for this LCD.

[LCD Type 2] — Channel paralleling required

  • LEDs per string : 9 in series
  • Vf per string : 24.3V – 30.6V
  • Number of strings: 1 (physically 4 parallel strings,
    but treated as a single combined string)
  • Total current : 440 mA
  • Since each channel can drive up to 200 mA, a minimum of
    3 channels need to be connected together to drive this
    string at 440 mA.

[LCD Type 3] — Channel paralleling required

  • LEDs per string : 6 in series
  • Vf per string : 18V – 21V
  • Number of strings: 1 (physically 4 parallel strings,
    but treated as a single combined string)
  • Total current : 200 mA
  • A single channel can handle 200 mA, so no channel
    paralleling is required for this LCD.

==============================================

  1. APPLICATION DETAILS
  • LED usage : LCD backlight
  • Display size : 7-inch or 15.1-inch (varies by product)
  • Operating temp: −10°C to +60°C (ambient)

==============================================

SUMMARY OF MY QUESTIONS

  1. Does the MP3394S support connecting multiple LEDx pins to a
    single LED string (same as the MPQ3369 feature “Allow to
    Connect Multiple LEDx Pins for One LED String”)?

  2. If yes, could you provide any recommended circuit or design
    guidelines for the MP3394S in this configuration? In particular:

    • ISET resistor configuration when channels are paralleled
    • Current balancing between paralleled channels
    • Open/short LED protection behavior

Thank you for your continued support.

Best regards,
Syuhei Makino