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LM2903-Q1: Schematic review

CHO SR
Genius 3215 points
Part Number: LM2903-Q1

Hi, 

My client requested a schematic review.

OUTPUT1 : 4.5V High

OUTPUT2 : 1.2V High

The purpose is to output the low output of the final PWM_EN stage.

Please review the schematic.

  • 0
    TI__Intellectual 2900 points

    Hi Cho,

    Currently, your 1IN- voltage is 0.496V and your 2IN- voltage is 1.210V. This means that Output will pull low whenever Total_Current is < 0.496V and high whenever Total_Current is >0.496V. 2OUT will pull low whenever HV_ADC is < 1.210V and high whenever HV_ADC is >1.210V.

    The LM2903-Q1 has an input common mode voltage requirement of V- to VCC - 2V over temperature; this means that you will need to keep your input voltages within that range to ensure proper operation of the comparator. Both IN- are within the range, but you need to ensure that Total_Current and HV_ADC are also within the range.

    The pre-biased PNP seems pretty redundant to me; is there a specific reason why you selected to have them in the design? If the output of the comparator pulls low, it turns on the PNP which pulls PWM_EN low. There is no inverting operation done by the PNP, so it seems to me that you could reduce your components by tying the comparator outputs together and adding a singular pull-up resistor for them to share.