LM2903: LM2903 and LM2903B start up timing difference

Scarlett Cao

Part Number: LM2903

Tool/software:

Hi team,

is there any start up timing difference between LM2903 and LM2903B?

Customer ask this because when they change from LM2903 to p2p LM2903B they found false comparator trip. Their application is below circuit, for LM2903B-Q1 seems when 5V applies, BJT pulls down pin2 first, then LM2903B starts up and output high.

Thanks

Scarlett

5 months ago

0 Clemens Ladisch 5 months ago

Guru 317280 points

This appears to be an attempt to add positive feedback at the inverting input. Is this the case?

What is the initial voltage of VIN? Can you show an oscilloscope trace?

The LM2903B has an additional invering step, compared to the LM2903, so it is plausible that the start-up behaviour is different.

0 Ron Michallick 5 months ago

TI__Guru**** 165176 points

Scarlett,

See application note for comparator, [APP] Design Guidelines for Devices with LM339/LM393 Cores During power up, VCM range will be out of specification, so output may be low or high depending on PCN version.

Amplifiers

Amplifiers forum

LM2903: LM2903 and LM2903B start up timing difference