LMZ31710X2EVM: LMZ31710X2EVM

Rony Koodalil Kuriakose

Prodigy 90 points

Part Number: LMZ31710X2EVM

I am testing the LMZ313710X2 evaluation board.

I have a issue measuring the correct current across the sense resistors of 1mOhm (R9,R10).

I am using HAMEG HM7042 power supply to supply input voltage of 12V, I set the output voltage via jumper to 1.8V.

I am feeding a external clock input of 300kHz to synchronize two devices on the evaluation board.

I should be reading across the 1mOhm resistor arnd ~8mV-9mV using DMM but get 0 on both devices.

Is there something I am missing tosetup or add for correct operation and test to get desired output currents from devices?

Please advise

Thanks

over 8 years ago

0 JohnTucker over 8 years ago

TI__Guru**** 191445 points

What is your load? If there is no load applied, then the output current will be near zero and you will not read any voltage across the current sense resistors.

0 Rony Koodalil Kuriakose over 8 years ago in reply to JohnTucker

Prodigy 90 points

Ok that clarifies that issue for me.

I have a DC load (ELA505 zentro-elekrik) connected to output of evaluation board. I switch it on and it reads the output voltage of 1.8V
When I start setting the current for dc load to draw - once I reach ~2A it switches my input power supply off (My input supply is Hameg HM7042)
Is the input [power supply insufficient or can you suggest why my DC-load shorting once it reaches 2A

0 J Arrigo over 8 years ago in reply to Rony Koodalil Kuriakose

TI__Mastermind 28020 points

What is the current rating of the input power supply? Check to see if it is going into current limit.

0 Rony Koodalil Kuriakose over 8 years ago in reply to J Arrigo

Prodigy 90 points

with respect to your suggestion, I replaced my power supply to handle higher current rating as the one I was using was low at 3.3A.

I had a look at the soft-start feature for the evaluation board and it is set such that the output voltage rise time is 1.2ms.
Is it possible to achieve a rise time of 150us by connecting a capacitor to the SS pin to ground or is there a minimum default rise time for this device especially in parallel configuration?

0 J Arrigo over 8 years ago in reply to Rony Koodalil Kuriakose

TI__Mastermind 28020 points

The SS time can be adjusted by changing the SS capacitor. Internal to the module, a SS capacitor is already present between SS/TR pin and STSEL. In order to reduce the SS time below 1.2ms, the STSEL pin would need to be removed from ground.

I do not recommend reducing the SS time too much as a quick rise time can cause large currents at start-up and the device may go into current limit when charging output capacitors.

Power management

Power management forum

LMZ31710X2EVM: LMZ31710X2EVM