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february 2011 doc id 14923 rev 1 1/25 AN2813 application note tde1708dft in io-link applications 1 introduction this application note investigates the possibility of using a tde1708dft switch for the physical layer transmitter realization of 3-wire io-link sensors. the tde1708dft is an integrated power switch especially dedicated to proximity detectors. it can deliver up to 250 ma, enables high-side and low-side configurations and includes a number of protections. according to the io-link communication specification (see section 8: references - 3. and for the tde1708dft features - see section 8: references - 1. ) two basic slave transmitter configurations were tested (see figure 1 ): p-switching (high-side) driver p-switching driver with an additional n-switching (low-side) driver (push-pull operation) figure 1. p-switching slave drive and p-switching with n-switching slave drive in the following test arrangements the input load current (ill m ) is fixed to 10 ma which represents the average master current sink value specified for a 3-wire system. the master (cq m ), slave (cq l ), and line capacitances are set together at 4.7 nf, corresponding to the maximum parasitic capacitance of the system. slave master line on off , ,n # 1 !- #1 3 #1 3 #1 - #1 - ),, - ),, - slave master line , ,n # 1 on off on off p switchingslavedrive p switchingwithn switchingslavedrive r www.st.com
contents AN2813 2/25 doc id 14923 rev 1 contents 1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 tde1708dft in high-side configuration . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1 high-side configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 high-side configuration with a capacitive load . . . . . . . . . . . . . . . . . . . . . . 7 3 tde1708dft in low-side configuration . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.1 low-side configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.2 low-side configuration with a capacitive load . . . . . . . . . . . . . . . . . . . . . 11 4 push-pull configuration with tde1708dft . . . . . . . . . . . . . . . . . . . . . . 13 5 performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.1 dynamic information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.2 temperature characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6 alternative driving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 6.1 temperature characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 7 conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 8 references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 9 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
AN2813 list of tables doc id 14923 rev 1 3/25 list of tables table 1. push-pull configuration dynamic information (v cc = 24 v; t j = 25 c; c l = 4.7 nf) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 table 2. dynamic information (v cc = 24 v; t j = 25 c; i l = 10 ma) . . . . . . . . . . . . . . . . . . . . . . . . 18 table 3. document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
list of figures AN2813 4/25 doc id 14923 rev 1 list of figures figure 1. p-switching slave drive and p-switching with n-switching slave drive. . . . . . . . . . . . . . . . . . 1 figure 2. high-side switch test configuration schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 figure 3. high-side switch configuration turn-on behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 figure 4. high-side switch configuration turn-off behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 figure 5. high-side switch test configuration schematic with a capacitive load . . . . . . . . . . . . . . . . . . 7 figure 6. high-side switch configuration with a capacitive load turn-on behavior . . . . . . . . . . . . . . . . 8 figure 7. high-side switch configuration with a capacitive load turn-off behavior . . . . . . . . . . . . . . . . 8 figure 8. low-side switch test configuration schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 figure 9. low-side switch configuration turn-on behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 figure 10. low-side switch configuration turn-off behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 figure 11. low-side switch test configuration schematic with a capacitive load . . . . . . . . . . . . . . . . . 11 figure 12. low-side switch configuration with a capacitive load turn-on behavior . . . . . . . . . . . . . . . 12 figure 13. low-side switch configuration with capacitive load turn-off behavior . . . . . . . . . . . . . . . . . 12 figure 14. push-pull test configuration schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 figure 15. push-pull configuration with capacitive load rising edge . . . . . . . . . . . . . . . . . . . . . . . . . . 15 figure 16. push-pull configuration with capacitive load falling edge . . . . . . . . . . . . . . . . . . . . . . . . . . 16 figure 17. software timing example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 figure 18. propagation turn-on time vs. temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 figure 19. propagation turn-off time vs. temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 8 figure 20. alternative driving schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 figure 21. alternative driving timings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 figure 22. delay propagation turn-on time vs. temperature (h. s. configuration) . . . . . . . . . . . . . . . . 22 figure 23. delay propagation turn-on time vs. temperature (l. s. configuration) . . . . . . . . . . . . . . . . 22 figure 24. propagation turn-off time vs. temperature (h. s. configuration) . . . . . . . . . . . . . . . . . . . . . 23 figure 25. propagation turn-off time vs. temperature (l. s. configuration) . . . . . . . . . . . . . . . . . . . . . 23
AN2813 tde1708dft in high-side configuration doc id 14923 rev 1 5/25 2 tde1708dft in high-side configuration 2.1 high-side configuration figure 2. high-side switch test configuration schematic ,%$$2)6%2 (3/54 $%,!9 '.$ ). 6 2%' 6 6s , 3/54 5 4$%$&4 '.$ '.$ '.$ n& # n& # 6 ## 1 "# $ 43 2 # '.$ '.$ '.$ 6 ## currentsinkm! generator voltage level 6 pulse width frequencyk( z '.$ $ "!4 ).054 /54054 !- highsidedriver
tde1708dft in high-side configuration AN2813 6/25 doc id 14923 rev 1 figure 3. high-side switch configuration turn-on behavior (1) 1. ch1: input voltage, ch2: output voltage, ch4: output current (x10). figure 4. high-side switch configuration turn-off behavior (1) 1. ch1: input voltage, ch2: output voltage, ch4: output current (x10).
AN2813 tde1708dft in high-side configuration doc id 14923 rev 1 7/25 2.2 high-side configuration with a capacitive load figure 5. high-side switch test configuration schematic with a capacitive load ,%$$2)6%2 (3/54 $%,!9 '.$ ). 6 2%' 6 6s , 3/54 5 4$%$&4 '.$ '.$ '.$ n& # 6 ## 1 "# $ 43 2 2 ?& # '.$ '.$ '.$ 6 ## current sinkm! generator voltagelevel 6 pulsewidth frequencyk(z '.$ n& # '.$ n& # #1 $ "!4 /54054 !- ).054 highsidedriver
tde1708dft in high-side configuration AN2813 8/25 doc id 14923 rev 1 figure 6. high-side switch configuration with a capacitive load turn-on behavior (1) 1. ch1: input voltage, ch2: output voltage, ch4: output current (x10). figure 7. high-side switch configuration with a capacitive load turn-off behavior (1) 1. ch1: input voltage, ch2: output voltage, ch4: output current (x10).
AN2813 tde1708dft in low-side configuration doc id 14923 rev 1 9/25 3 tde1708dft in low-side configuration 3.1 low-side configuration figure 8. low-side switch test configuration schematic ,%$$2)6%2 (3/54 $%,!9 '.$ ). 6 2%' 6 6s , 3/54 5 4$%$&4 '.$ '.$ '.$ n& # n& # 6 ## $ 43 2 2 # '.$ 6 ## current sourcem! lowsidedriver generator voltagelevel6 pulsewidth frequencyk(z '.$ 1 "# 6 ## 6 ## $ "!4 /54054 !- ).054
tde1708dft in low-side configuration AN2813 10/25 doc id 14923 rev 1 figure 9. low-side switch configuration turn-on behavior (1) 1. ch1: input voltage, ch2: output voltage, ch4: output current (x10). figure 10. low-side switch configuration turn-off behavior (1) 1. ch1: input voltage, ch2: output voltage, ch4: output current (x10).
AN2813 tde1708dft in low-side configuration doc id 14923 rev 1 11/25 3.2 low-side configuration with a capacitive load figure 11. low-side switch test configuration schematic with a capacitive load ,%$$2)6%2 (3/54 $%,!9 '.$ ). 6 2%' 6 6s , 3/54 5 4$%$&4 '.$ '.$ '.$ n& # n& # 6 ## $ 43 2 2 # '.$ 6 ## currentsourcem! lowsidedriver generator voltage level6 pulsewidth frequencyk(z '.$ 1 "# 6 ## 6 ## $ "!4 n& # '.$ #1 /54054 !- ).054
tde1708dft in low-side configuration AN2813 12/25 doc id 14923 rev 1 figure 12. low-side switch configuration with a capacitive load turn-on behavior (1) 1. ch1: input voltage, ch2: output voltage, ch4: output current (x10). figure 13. low-side switch configuration with capacitive load turn-off behavior (1) 1. ch1: input voltage, ch2: output voltage, ch4: output current (x10).
AN2813 push-pull configuration with tde1708dft doc id 14923 rev 1 13/25 4 push-pull configuration with tde1708dft the following push-pull driver configuration was designed based on the previous single driver measurements. in this proposed schematic (see figure 14 ) two additional components (r3, d3) must be added to speed up the turning off of the driver in the low-side configuration. the resistor r3 creates a weak pull-up while the diode d3 separates the low- side output from the high-side. the reason for this being that if the low-side driver is forced high in a short time after turning off then it stays turned on with all the subsequent effects.
push-pull configuration with tde1708dft AN2813 14/25 doc id 14923 rev 1 figure 14. push-pull test configuration schematic the low-side driver helps to reduce the falling time with the capacitive load, the rest of the circuit works exactly the same way as that described in section 2.1 . figure 17 shows a software timing example in accordance with table 2 and a dead time between the driver outputs of 1 s. ,%$$2)6%2 (3/54 $%,!9 '.$ ). 6 2%' 6 6s , 3/54 5 4$%$&4 '.$ '.$ '.$ n& # 6 ## 1 "# $ 43 2 2 # '.$ '.$ '.$ 6 ## current sinkm! highsidedriver generator voltagelevel 6 pulsewidth frequencyk(z '.$ ,%$$2)6%2 (3/54 $%,!9 '.$ ). 6 2%' 6 6s , 3/54 5 4$%$&4 '.$ '.$ '.$ n& # 6 ## lowsidedriver n& # '.$ n& # n& # #1 $ "!4 $ "!4 2 6 ## (3 /54054 , 3/54054 !- (3).054 ,3).054
AN2813 push-pull configuration with tde1708dft doc id 14923 rev 1 15/25 figure 15. push-pull configuration with capacitive load rising edge (1) 1. ch1: input voltage, ch2: (h. s.) output voltage, ch3: input voltage, ch4: (l. s.) output voltage. table 1. push-pull configuration dynamic information (v cc = 24 v; t j = 25 c; c l = 4.7 nf) test conditions min typ max unit turn-on time v i = 0 to 5 v 800 ns turn-off time v i = 0 to 5 v 2 s
push-pull configuration with tde1708dft AN2813 16/25 doc id 14923 rev 1 figure 16. push-pull configuration with capacitive load falling edge (1) 1. ch1: input voltage, ch2: (h. s.) output voltage, ch3: input voltage, ch4: (l. s.) output voltage.
AN2813 push-pull configuration with tde1708dft doc id 14923 rev 1 17/25 figure 17. software timing example
performance characteristics AN2813 18/25 doc id 14923 rev 1 5 performance characteristics 5.1 dynamic information 5.2 temperature characteristics figure 18. propagation turn-on time vs. temperature figure 19. propagation turn-off time vs. temperature table 2. dynamic information (v cc = 24 v; t j = 25 c; i l = 10 ma) test conditions min typ max unit propagation turn-on time v i = 0 to 5 v 16 s propagation turn-off time v i = 0 to 5 v 8 s n n 4emperature?# !- n n 4emperature?# !-
AN2813 alternative driving doc id 14923 rev 1 19/25 6 alternative driving the larger temperature propagation turn-on time dependence of the tde1708dft, described in the previous section ( section 5: performance characteristics ), has led to the development of an alternative kind of driving which would not suffer from this problem. the presented driving configuration (see figure 20 ) uses both the input signal ?in? together with the open collector pin ?delay? (originally dedicated to delay adjustment). the in signal controls only the turning off of the switch (the output is blocked by the delay pin during its high state), while the delay signal then controls the turning on of the switch (see figure 21 ). this principle results in more positive temperature characteristics ( section 6.1: temperature characteristics ).
alternative driving AN2813 20/25 doc id 14923 rev 1 figure 20. alternative driving schematics 1. the resistor r1 prevents the circuit from the cross conduction between the push-pull output of the generator and the open collector delay pin. ,%$$2)6%2 (3/54 $%,!9 '.$ ). 6 2%' 6 6s ,3/54 5 4$%$&4 '.$ '.$ '.$ n& # n& # 6 ## driver generator voltage level 6 pulse width frequencyk(z '.$ ).054 2 !-
AN2813 alternative driving doc id 14923 rev 1 21/25 figure 21. alternative driving timings 1. delay propagation turn-on time (see figure 22 and figure 23 ). 2. propagation turn-off time (see figure 24 and figure 25 ). 3. state 1: delay releases the output. 4. state 3: in goes low and turns off the switch. 5. state 4: in goes high, the output is blocked by the delay signal (the monostable circuit time meanwhile runs). !- $%,!9 ). /54 /&& /. 3tate 3tate 3tate 3tate 3tate 3tate 3tate 3tate 3tate ?s
alternative driving AN2813 22/25 doc id 14923 rev 1 6.1 temperature characteristics figure 22. delay propagation turn-on time vs. temperature (h. s. configuration) figure 23. delay propagation turn-on time vs. temperature (l. s. configuration) n n 4emperature?# !- n n 4emperature?# !-
AN2813 alternative driving doc id 14923 rev 1 23/25 figure 24. propagation turn-off time vs. temperature (h. s. configuration) figure 25. propagation turn-off time vs. temperature (l. s. configuration) n n 4emperature?# !- n n 4emperature?# !-
conclusion AN2813 24/25 doc id 14923 rev 1 7 conclusion with respect to the results obtained, the tde1708dft may be used in the operating mode com1 (4.8 kbaud) in p-switching (high-side) 3-wire sensors and up to operating mode com2 (38.4 kbaud) in push-pull 3-wire sensors. note: in the case of push-pull configuration a precise compensation of the propagation turn-on time temperature drift ( figure 18 ) is necessary to avoid cross conduction of the two switches. the alternative driving configuration ( section 6: alternative driving ) partially solves this issue for the price of employing two input pins for one switch. 8 references 1. tde1708dft datasheet. 2. an495 application note. 3. io-link communication specification, version 0.98, february 2007 - see: www.io-link.com/share/downloads/iol-comm-spec_10002_v10_090118.pdf. 9 revision history table 3. document revision history date revision changes 09-feb-2011 1 initial release.
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