Hello EEs,
I have ordered the following JK flip-flops:
http://www.ti.com/lit/ds/symlink/sn74hc109.pdf
(the SN74HC109 version) and
https://media.digikey.com/pdf/Data Sheets/ST Microelectronics PDFS/M74HC112.pdf
encouraged by the advertised low quiescent supply current (Icc) at room temperature: 4 uA in the first (page 4) and 2 uA in the second (also page 4). In any case, both manufacturers promise that in absolutely worst case the Icc should not exceed 40 uA.
To my dismay, the actually measured Icc was 3-4 orders of magnitude higher than that! First, I've made a vanilla measurement with just power pins connected, as illustrated in the first circuit in the attached figure:
Then I noticed the "VI = VCC or GND" note in "Test condition" column. Well, fair enough: with inputs flapping in the breeze the flip-flop may be oscillating internally which would explain extra energy draw. Therefore, I connected both as intended (second circuit). Essentially, all the inputs are now tied to Vcc and both Q and Q' are now stable (LOW and HIGH, respectively, upon powering up). It didn't matter though: the ammeter still showed Icc = 1000-12000 uA for the first JK and 1000-25000 uA for the second. In both cases the current was swinging wildly between these ranges.
Are both manufacturers lying through their teeth in the data sheets? Or is it me who is doing something wrong?
(I want to use the JK as a Q toggle driven in actual circuit by an external clock rather than the switch SW1 used here for testing.)
Thank you in advance for your valuable experience in this matter.
I have ordered the following JK flip-flops:
http://www.ti.com/lit/ds/symlink/sn74hc109.pdf
(the SN74HC109 version) and
https://media.digikey.com/pdf/Data Sheets/ST Microelectronics PDFS/M74HC112.pdf
encouraged by the advertised low quiescent supply current (Icc) at room temperature: 4 uA in the first (page 4) and 2 uA in the second (also page 4). In any case, both manufacturers promise that in absolutely worst case the Icc should not exceed 40 uA.
To my dismay, the actually measured Icc was 3-4 orders of magnitude higher than that! First, I've made a vanilla measurement with just power pins connected, as illustrated in the first circuit in the attached figure:
Then I noticed the "VI = VCC or GND" note in "Test condition" column. Well, fair enough: with inputs flapping in the breeze the flip-flop may be oscillating internally which would explain extra energy draw. Therefore, I connected both as intended (second circuit). Essentially, all the inputs are now tied to Vcc and both Q and Q' are now stable (LOW and HIGH, respectively, upon powering up). It didn't matter though: the ammeter still showed Icc = 1000-12000 uA for the first JK and 1000-25000 uA for the second. In both cases the current was swinging wildly between these ranges.
Are both manufacturers lying through their teeth in the data sheets? Or is it me who is doing something wrong?
(I want to use the JK as a Q toggle driven in actual circuit by an external clock rather than the switch SW1 used here for testing.)
Thank you in advance for your valuable experience in this matter.
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