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LTC4417 hysteresis

Question asked by carpo27 on Dec 22, 2017
Latest reply on Jan 8, 2018 by daniel.castelo@livetools.tv

We are using the LTC4417CUF device in a prototype with input protection and prioritization.

 

We are using batteries and tried to set hysteresis manually, with an external resistor on HYS pin. See schematic extract here below.

 

First tests confirm correct OV(rising) and UV(falling) thresholds, around 20V and 6.1V as shown in schematic comments.

Nevertheless, the hysteresis is far bigger than expected, with OV(falling) = 15.4V and UV(rising) = 8.8V.

 

V_HYS has been measured at ~ 0.5V, thus seems correct (see datasheet, page 4). R111 = 162K has been verified.

I_HYS is thus = 3.08 uA, which should correspond to I_OV_UV = 390 nA (equation 1-28).

 

The observed hysteresis voltages deltas are 8 times higher than expected; are you sure of the 1-to-8 relationship between I_HYS and the current sinked/sourced by OVx/UVx?

 

Thanks, kind regards

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