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# TPS55010: TPS55010

Part Number: TPS55010
Other Parts Discussed in Thread: PMP4440

Hi,

I would like to design isolation power with below,

Input voltage:5V

Output voltage: 5V

Output current: 300mA.

It seems that TPS55010 cannot support output current of 300mA.

Could you please provide suitable isolation solution to me?

Sincerely,

Chin

• Hi Chin,

The TPS55010 can support 5 Vin to 5 Vout at 300 mA. The datasheet curves actually provide data all the way up to this load current. When using the TPS55010 with this much load current, make sure to be aware of how the output voltage changes with load.

Best Regards,
Anthony
• Hi Anthony,
1. According to the figure2 of EVM (www.ti.com/.../slvu459a.pdf), the output voltage is about 6V when no load on the output.
When load is 300mA ,output voltage is 4.6V. There is a 5.6V zener diode on the output,but why the output doesn't fix on 5.6V?
2. If I would like to fix a voltage(under 6V) before real load sink current , can I connect a resister between Vout and GND ?
Thanks!
Chin
• Hi Chin,

The voltage goes up to 6 V likely due to the voltage drop across the 200 Ω resistor (R4). With 6 V output and 5.6 V zener voltage, the voltage drop across the resistor would be 0.4 V. This gives a current of 0.4 V/200 Ω = 2 mA.

A resistor to ground could also be used. Assuming my 2 mA calculation above is correct, a 3 kΩ resistor would give the same effect. I calculated this from 6 V/2 mA. The disadvantage of using a resistor is it will always be loading the output dissipating a little bit of power. When a zener diode is used there is no power dissipation when the output voltage is below the zener voltage.

Anthony
• Hi Anthony,

Also need to discuss below items with you.

1. I saw the different placement of dot on primary side and secondary side between PMP4440 schematic and transformer datasheet.(see attached)

2.We will design in the MTC-0029SG in our desig with output 5V@ 300mA and input is 5V, do you have any comment or suggestion?

Sincerely

Chin

MTC-0029SG_PMP4440.docx

• Hi Chin,

The dot orientation is effectively the same since both the primary and secondary orientation are reversed. The issue is the pinout is different. The transformer used on PMP4440 shows two secondary winding's in series while the MTC datasheet shows just a single winding from pin 5 to 8. This also would not make a difference because in both versions the entire secondary goes from pin 5 to pin 8. The only difference is whether you need to connect pin 6 to pin 7 on the schematic or not.

If you want to double check this, you will have to check with MTC. I don't have any more details on this transformer other than what is shown on the datasheet on the web.

Best Regards,
Anthony