if the voltage supply Vs is over 15V in many devices I can't reset the latch comparator or if I send a reset pulse the device goes in fault and is not possible to reset
Could you be a bit more specific about what product group you are using so that I can make sure your question is placed in the correct forum? This way you will get a response sooner rather than later. Thanks!
E2E Community Moderator, Texas Instruments
I think that the product group is Precision Amplifiers
Can you please provide us with a schematic?
Precision Analog Applications
following the schematics.
I use about 43 blocks like this and the problem comes if the "V13" that supply the INA201 is over 14,8 -15 V. About the half of the INA201 comparator output is pulled down to gnd also if the input voltage of the comparator is 0 (less then 0.6V of the ref). It's possible that the internal Vref go wrong. When I reset the INA201 comparator the output ( pin6 ) in some device toggles gnd - pull up.
Thanks for the schematic.
It appears as though the output voltage is heavily divided down. Can you please help me understand your typical use case? For example, I see the shunt is 3mohms. In order to meet the 20mV shunt voltage requirement for linear operation, your minimum current must be 6.7A. The output can swing to 12.75V with a 13V supply, therefore your maximum load current is 85A. Correct? Also, what is the impedance of I_J4_OUT_20A_HS_1?
I see a differential filter on the input using 100ohm resistors. Please note that we recommend making these as small as possible. The cutoff frequency of the input filter is set to ~8kHz, so you could reduce the resistors to 10ohms and increase the capacitor to 1uF.
There is also a 470pF cap on pin 3 of the device (the comparator input). What is this for?
Thanks for your support,
The typical use is for 24V automotive output switch. I have different current range from 2A to 20A. I need to monitor the current but also protect the MOS from max overcurrent. The load are different : lamp, DC motor, valve and many of these have a peak current at switch on ( inrush current when there are input capacitor or cold lamp). So to avoid the max load current at switch ON I need to increase the voltage supply and over 15V I have this surprise. Many INA201 output comparator don't follow the logical input signal and also after the reset pulse don't respect the specification.
About the differential filter I don't use it and the 100nF capacitor is not installed, there are the 100Ohm in series with sense input but I can remove. The 470pF on pin 3 is for a short delay but also this can be removed.
Thanks for the additional information.
I have tried to recreate your issue with the comparator in my lab but have not succeeded. The device was supplied with 13V and the comparator output pulls up to 5V through a 4.7kohm resistor. The comparator output behaves as I would expect.
I then changed the supply voltage to 18V, and the comparator output behaves as I would expect.
Therefore, perhaps there's a misunderstanding with respect to the comparator behavior. Please note the comparator output is latched. When pin 5 is low, the latch is transparent. When pin 5 is high, the output is latched and will not change if the input goes low. Pin 5 must go low to change the output. This behavior is shown in Figure 30 of the datasheet.
I hope this helps.
the problem comes out on about half of the device that I have so it's possible that the INA201 you are testing is ok.
The use of the pin 5 is clear, I use it to latch the comparator. The strange thing if I increase the supply voltage over 15V and I give some rest pulse on pin 5 the comparator output toggles up and down with input = 0.
One question, do you think possible that the components are not original TI but a bad copy ??? I buy them from official supplier but in the past with other component I have this surprise
A couple of quick questions:
1) Have you tried swapping devices from a functional circuit to a non-functional circuit? In other words, does this behavior follow the device or the circuit?
2) Have you removed one of the 'bad' devices from your circuit and verified this behavior independent of the application? If so, please send me a schematic of your test circuit.
Please note that when I ran my tests, I did not use the current shunt portion of the INA201. I was under the impression that the issue revolved around the supply voltage and comparator. In order to isolate the comparator, please disconnect the current shunt from the comparator by removing the 56kohm, 4.7kohm, and 470pF passives. Then apply a voltage to the test point connected to pin 3 of the INA201 and monitor pin 6. I would connect pin 5 to ground and verify transparent operation of the comparator. Do this for both Vs=13 and Vs>=15. Please let me know the results.
I go on with my test, and finally I find the problem. I see that the problem come from the reset pulse front. I drive the reset signal with an SN74LVC1G17 and the signal front are very quick. I have added a capacitor (47nF) on the reset signal to smooth the front and the problem disappear. So is the rise front of the reset signal that in some way affect the comparator. During the test I have shorted the comparator input to 0V.
Probably you can recreate the same situation on your bench test to confirm the criticity
Thanks for the feedback...it is good to hear your problem has been resolved.
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