In this case you need a buck converter with high side sense. Check out the LM3409. It is designed to be able to do much more power, but it is a controller so for these current levels you could have a very small external FET, sense resistor, etc... and…
Hello Ryuji,
That is a good question. Basically the diode is not totally necessary, but it may be desirable depending on the application. If the LED stack voltage is less than VCC (or the 5V rail in the LM3409 schematic) then it is not really necessary…
My client is proposing to build an airport runway lighting product consisting of 20 LED drivers {LM3450/LM3409} in parallel. The issue is that for the various dimming steps all the parallel LED lamps must deliver the same lumens (+/-3%). The dimming step…
Hello Ryuji-san,
If you need that kind of accuracy and such a high PWM frequency your best bet is the TPS92641 with shunt FET dimming. The TPS92515 and LM3409 might also work but they do not have as much accuracy and I'm not sure they could meet the…
Hello Beppe,
You can used that as a boost converter. For the Matrix portion a hysteretic part such as the TPS92515 or TPS92518 or even the LM3409 would be good choices for the buck portion. Boost to higher voltage than 36V (12 x 3V) then buck that…
Dear, Clinton-san.
I appreciate your valuable information.
May I confirm several things?
1. Vcc-UVLO(increasing) = typ. 3.73V and Vcc-HYS = 0.283V
So, Vcc-UVLO(decreasing) will be typ.3.447V.
If VCC to drive 10mA, Vin across Vcc-UVLO(decreasing…
Hello,
If your input range is 12-30 volts and is non-adjustable (such as a battery) and your LED load happened to be near 12 volts the efficiency at 30 volts would be 40%. If the LED load is 12 watts 18 watts would have to be dissipated in the linear…
Hello,
If they are trying to PWM dim at 20 KHz this is probably the wrong approach. The waveforms attached look like they should for what they are donig. The inductor slew rate won't be fast enough for accurate dimming and may actually miss a portion…
Hello Nicky,
It sounds like a thermal issue to me, it usually is if it runs fine for a while then starts blinking. It's likely going into thermal shutdown. Are the part numbers in the schematic correct? If so I have two comments:
1. The FET you are…
