© 1999 Scenix Semiconductor, Inc. All rights reserved. - 25 - www.scenix.com SX18AC  / SX20AC / SX28AC Note  1:   The external Power-On Reset circuit is required
only if V_dd power-up is too slow. The diode D helps dis-
charge the capacitor quickly when V_dd powers down. Note  2:   R  <  40  kW  is  recommended  to  make  sure  that
voltage drop across R does not violate the device electri-
cal specifications. Note  3:   R1 = 100W to 1kW  will  limit  any  current  flowing
into MCLR from external capacitor C. This helps prevent
MCLR   pin   breakdown   due   to   Electrostatic   Discharge
(ESD) or Electrical Overstress (EOS). 13.0 BROWN-OUT DETECTOR The   on-chip   brown-out   detection   circuitry   resets   the
device when V_dd dips below the specified brown-out volt-
age.  The  device  is  held  in  reset  as  long  as  V_dd  stays
below the brown-out voltage. The device will come out of
reset when V_dd  rises  above  the  brown-out  voltage.  The
brown-out  level  is  preset  to  approximately  4.2V  at  the
factory.  The  brown-out  circuit  can  be  disabled  through
BOR0 and BOR1 bits contained in the FUSEX Word reg-
ister. Figure 12-3. Time-out Sequence on Power-up (MCLR tied to V_dd): Fast V_dd Rise Time Figure 12-4. Time-out Sequence on Power-up (MCLR tied to V_dd): Slow Rise Time Figure  12-5. External Power-On Reset Circuit (For Slow V_dd Power-up) V_dd MCLR POR drt_time_out RESET Tdrt V_dd MCLR POR drt_time_out RESET Tdrt V1 V_dd R C MCLR D R1