How would the LP2951 error output behave during a 100ms power dip?
The output capacitor will have to try to hold the output up long enough to prevent it from falling too low in order to prevent the flag from going low. For example, assume the output is set to 3.7V. The error flag can activate at a voltage as high as 25 mV below the 1.23V reference, which is 75 mV below the 5V output. So, the output capacitor should allow the output to droop NOT MORE than 75 mV in the 10 ms interval at the rated load current. If the load current, for example, is 50 µA: I = C dV/dT, 50 µA = C x 0.075/0.01 It follows that the output capacitor must be not smaller than about 7 microfarads. Since the output capacitor is 100µF, the output should stay up long enough that the flag will not activate during the transient. There is one word of caution: If the voltage dip on the Vin line is very fast (fast fall time), it will couple through the internal circuitry and cause a deviation in the reference voltage, which can cause a brief activation of the error flag. The way to preven
