TPSM5D1806: Output Voltage Setting from 12Vin

Hirotsugu Kobayashi

Part Number: TPSM5D1806
Other Parts Discussed in Thread: TPS541620

Hi team,

I want to output 1.2V and 5V from 12Vin with TPSM5D1806. The current is 4A each.
The data sheet states that 2MHz is required to obtain 5V, but it must be 1.5MHz or less to obtain 1.2V.
Does that mean that 1.2V and 5V cannot be output from 12Vin?

Best Regards,

over 2 years ago

0 David_Daniels over 2 years ago

TI__Genius 16495 points

That is correct. The minimum on time, off time, switching frequency and inductor value set a boundary for output voltage range. Table 7-1 shows at 2MHz that 5.5V and 1.4V is possible.

0 David_Daniels over 2 years ago in reply to David_Daniels

TI__Genius 16495 points

You can use the https://www.ti.com/product/TPS541620 which is a converter.

Using two different inductor values you should be able to get 1.2V and 5V.

0 Hirotsugu Kobayashi over 2 years ago in reply to David_Daniels

Mastermind 8475 points

I understand that the minimum value is due to Ton_min, but I'm not sure about the maximum value constraint.
If it is 12Vin, the Toff constraint will not be applied.
It may be restricted by the Current Limit, but if it is 0.47uH, I think that 5V/4A can be output at 1.5MHz.

0 David_Daniels over 2 years ago in reply to Hirotsugu Kobayashi

TI__Genius 16495 points

That is correct, the limitation on the 1.2V is from the minimum ton. Toff will limit the minimum input voltages for the higher output voltage.

0 Hirotsugu Kobayashi over 2 years ago in reply to David_Daniels

Mastermind 8475 points

If the internal IC of TPSM5D1806 is the same as TPS541620, Toff is 200ns.
At 12Vin and 1.5MHz, the maximum output voltage by Toff is 8.4V.
For 12Vin, 5Vout, 0.47uH, 1.5MHz, the inductor current is 4.14A.
If the internal overcurrent threshold is 8A, the maximum output current is 5.9A.
Why is it limited to 3.6Vout at 12Vin, 1.5MHz, <4A?