Lets have a comparison of supervisor chip MAX812-T and LPC932A1's Internal brown out.

LPC932A1 :
Brown out voltage = 2.40V to 2.70V provided Vcc= 2.4V to 3.6V

MAX812 :
Brown Out Voltage = 3.03V to 3.14V provided Vcc= 1V to 3.6V

(1) For LPC932A1 the internal brown out reset will occur only if supply voltage is still above 2.4V what if the supply voltage becomes 2.3V or say 2V. The internal supervisor will fail and micro might continue doing crazy things. With MAX812 the brown out reset will remain active as long as Vcc>=1V. So even if the supply falls down to 1V the supervisor is still alive and will keep the micro under reset condition. There are some supervisor that gives RESET down to 0V supply voltage.

(2) Its said that inbuilt brown out response time is poor. Thus the internal brown out may not give any response for short supply dip. The Reset Delay chart is not there in LPC932A1 datasheet and User manual. But the Rst Delay char is there in MAX812 datasheet.

(3)Most of the digital IC's have a supply tolerance of 10%. The minimum Vbo for LPC932A1 is 2.4Volts and your board might be having a lot of other digital chips which might not work down to 2.4Volts. With MAX812-T minimum Vbo= 3.03V and at this voltage all the 3V/3.3V digital IC's will work happily.

(4)The LPC932A1 datasheet gives such a wide band [ chip to chip variation] for Vbo [ brown out voltage ] thus in some micro the tripping may occur at 2.7Volts where as in some other at 2.4Volts. This tolerance is 12.5%. Where as with MAX812 this tolerance is 3.07%.

Regards,
Prahlad Purohit