ALT CROSSING RESTR NOT MET WHEN ALT UNDERSHOT DURING DSCNT FOR ILS RWY 06 OUTSIDE OF DANDY INTXN; 6 NM SW OF TEB; NJ.

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WE HAD BEEN ASSIGNED THE ILS RWY 06 AT TEB. MY FO AND I COMPLETED OUR DSCNT CHKLIST THAT INCLUDED AN APCH BRIEFING. WE BOTH CAUGHT THAT THERE WAS A MANDATORY CROSSING ALT TO THE FIX PRIOR TO THE FINAL APCH FIX. ON THE CHART IT APPEARED THAT THIS FIX WOULD BE CROSSED AT THE CORRECT ALT IF ONE FLEW ON THE GS. THE MANDATORY CROSSING ALT WAS 1500 FT MSL. WE WERE ALREADY ON THE LOC WHEN ISSUED OUR APCH CLRNC OF 'DSND TO 2000 FT CLRED ILS 06 APCH.' I HAD DECIDED TO ALLOW THE AIRPLANE TO FLY THE APCH IN FMS/VNAV MODE TO THE FAF SO ALL ALT RESTRS WOULD BE MADE; BUT IT AUTOMATICALLY GOES TO SHORT RANGE NAV MODE WITH A STABLE SIGNAL FROM THE LOC/GS. THINKING THAT I'D CROSS THE MANDATORY ALT IF I SIMPLY STAYED ON THE GS; I ALLOWED THE AUTOPLT TO CONTINUE TRACKING THE LOC/GS IN SHORT RANGE NAV MODE. WE CROSSED THE MANDATORY CROSSING ALT FIX (DANDY) AT ABOUT 1800 FT MSL. CONTRIBUTING TO THIS DEV: BOTH CREW MEMBERS' FAILURE TO DETECT THAT DANDY'S MANDATORY CROSSING ALT WAS NOT ON THE GS. MY AIRLINE BACKGND AND FAMILIARITY WITH COMMERCIAL CHART PROFILE DEPICTION VERSUS NOS (NACO - SEC) PROFILE DEPICTIONS. NOS (NACO - SEC) PROFILE OF DSCNTS SHOWS ONE DSNDING LINE EVEN FOR STEP DOWNS. THE DEPICTION ON THE TEB ILS 06 SHOWS THE ALT PROFILE VERY CLOSE TO THE GS FEATHER. OTHER CHARTS AVOID CONFUSION BY SHOWING EACH STEP DOWN GRAPHICALLY WITH DSCNT AND LEVEL-OFFS PRIOR TO GS INTERCEPTION.