LMR16030: LMR16030 Wide IN, Wide OUT Efficiency

VolkerK

Part Number: LMR16030
Other Parts Discussed in Thread: LM46002, LMR16020

Hi,

we use the LMR16030 with 12V to 48V input and adjustable 6V to about 42V output. We adjust the switching frequency using external switched resistors. All works fine, except the temperature at 2A output current is too high.

Any idea for a solution with lower Rdson? We are not sure about the compensation, which is internal in the LMR16030, but most times external for others. With our requirements the COMP-circuit is diificult to calculate...

Thanks a lot for any hint!

Volker

over 8 years ago

0 Arief Hernadi over 8 years ago

TI__Mastermind 23845 points

What is the operating frequency that you are using?
You might lower the frequency to have a little more efficiency. Another option is to use LM46002 which has a better Rdson
www.ti.com/.../LM46002

thanks
-Arief

0 VolkerK over 8 years ago

Prodigy 170 points

PS: It's an LED application. So the load changes very, very slow...

0 VolkerK over 8 years ago in reply to Arief Hernadi

Prodigy 170 points

We adjust the frequency between 200kHz and 1MHz depending on the load. We'll have a look at the LM46002, thanks a lot!

0 VolkerK over 8 years ago in reply to VolkerK

Prodigy 170 points

LM46002 has a Voutmax of 28V. This is too low for us.

0 VolkerK over 8 years ago in reply to VolkerK

Prodigy 170 points

Currently we use only 2A from the LMR16030. Would it make any difference in temperature to use the LMR16020 in a 2A application?

0 Arief Hernadi over 8 years ago in reply to VolkerK

TI__Mastermind 23845 points

Hi,
I think the LMR16020 and LMR16030 the Rds on are the same therefore not much effect changing the part .
This part has a lower Rdson for the MOSFET
www.ti.com/.../tps54560b-q1.pdf

Thanks
-Arief

0 VolkerK over 8 years ago in reply to Arief Hernadi

Prodigy 170 points

Hi Arief,
thanks a lot! We already checked this part, but we don't know how to dimension the COMP-network for our wide requirements... Any ideas abou that?
Thanks
Volker

0 YangZhang over 8 years ago in reply to VolkerK

TI__Genius 11085 points

Can you explain in more detail about the Vout vs Iout conditions? With 42V output voltage and 2A current, it is 84W of output power.

Since you mentioned the frequency is adjusted in regards to output current, what is the frequency used at 2A load?

Is there a relation between Vout and VIN? Such as 42Vout will be seen when Vin is 48V, 6V will only appear with 12Vin, not 48Vin. The challenge is that you only have one inductor on the board. With such a wide range of Vin and Vout, the current ripple could be all over the place. 48V input voltage combined with 1MHz operation can generate quite some swithcing loss. I don't think Rds on is the only factor here.

0 VolkerK over 8 years ago in reply to YangZhang

Prodigy 170 points

We currently are trying to reduce our requirements. We use Vout to drive a load, which behaves a little bit like a resistor. The lower the voltage, the lower is also the output current.
In a typical high power scenario with Vin=48V, Vout ranges from 42V@2A downto 16V@10mA. So we need to optimize for the high voltage.
In future designs we won't be able to adjust the frequency. We tend to use 250kHz with a large inductor (47u). We also want to reduce the drop voltage (Vin to Vout) by definition, so that a 16V load is used with Vin=24V.

0 YangZhang over 8 years ago in reply to VolkerK

TI__Genius 11085 points

47uH seems reasonable with 250kHz design. The power loss at high Vout is mainly because of 48V input voltage and 2A load current. It would be helpful to use a thermal camera to see the temperature rising among the IC, diode and inductor, to determine which one is the hottest.

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LMR16030: LMR16030 Wide IN, Wide OUT Efficiency