INA206 RESETn latch

Thank you Jason,

That is very helpful. Just to verify how we will use this in our application. If RESET = HI:

The user will normally access the INA206 at comparator out.

(1) You write “if reset is high and VIN exceeds the limit, CMPout stays high until
VIN is below the limit AND reset is issued at that time.” Now pin 6 is open-drain
so a pull-up is called for. Does your statement really refer to point “x”?
This would be pin 6 tied to a pull-up.

That is, is it more correct to say “if VSNS > VTRIP then point “x” = HI”?

(2) Keeping RESET = HI, you write “if reset is high and VIN exceeds the limit,
CMPout stays high until VIN is below the limit AND reset is issued at that time.”
What does “reset is issued” mean? Does it mean power is toggled on/off?
The RESET pin is toggled LO? Or what?

(3) Again w RESET = HI, for the INA206 there are two comparators and a window comparator
can be configured (data sheet Fig 41)

When you write “if reset is high and VIN exceeds the limit, CMPout stays high until
VIN is below the limit AND reset is issued at that time” does this apply to both VUPR and VLWR?

That is, is point “x” = HI for BOTH cases: (1) when VIN > VUPR (shown in RED)
and (2) when VIN < VLWR (shown in GRN)? This is important for me to know.

In other words is point “x” = HI both when VIN rises ABOVE VUPR and in the case when VIN falls BELOW VLWR?

Thank you

Hi Jamaal,
Is there a attachment that you are referering to. Can you please retry attaching.

Sorry,

Moving too fast.  "x" is the comparator output.

Thanks

Hi Jamaal,
(1) For Comparator 1: RESET = high, Vin exceeds the limit CMPOUT = high and stays high until Vin is lower than limit and RESET = low. You can tie a pull up to reset and pull it low when needed or it can be directly switched between supply and ground as shown in figure 30.
RESET = low, Vin exceeds the limit CMPOUT = high and when Vin is lower than the limit CMPOUT = low. It's basically like a transparent mode.
(2) RESET = High means tie it to supply and RESET = low means tie it to ground.
(3) This is my undestanding:
Reset = low and when VIN < lower window voltage or when VIN > upper window voltage, the COMPOUT = Low and
when VIN is within lower and upper window voltage COMPOUT = high.
When Reset = high and Vin is within the upper and lower window voltage then COMPOUT = high and output will remain high for the case VIN < lower window voltage but COMPOUT = low for the case VIN > upper window voltage since the comparator 2 pulls the output low. So I think Reset should be low for the window comparator to work correctly.
But let me verify this and get back to you tomorrow.

Thanks Rabab,

A couple things to clarify, sorry...

(A)RESET = high, Vin exceeds the limit CMPOUT = high and stays high until Vin is lower than limit and RESET = low.

You can tie a pull up to reset and pull it low when needed or it can be directly switched between supply and ground as shown in figure 30.

 

Let the circuit be such that RESET = CMP_OUT = HI 

OK, so given this circuit arrangement clearing a fault (in other words, to clear CMP_OUT) requires TWO conditions: (a) V_{CMP_IN} > 0.6V AND (b) RESET must go LO.

The data sheet on page 6: “Comparator Power-on Reset Threshold = 1.5V”

“The comparator will be in reset as long as the power supply is below the voltage shown here. If CMP1 RESET is high at power-up, the comparator output comes up high and requires a reset to assume a low state, if appropriate.”

Our complication with that...we must manually assert RESET = GND at power-up at power-up, say, (or else CMP_OUT will never be cleared)?

(B)When Reset = high and Vin is within the upper and lower window voltage then COMPOUT = high and output will remain high for the case VIN < lower window voltage but COMPOUT = low for the case VIN > upper window voltage since the comparator 2 pulls the output low. So I think Reset should be low for the window comparator to work correctly.  But let me verify this and get back to you tomorrow.

If I correctly understand you I hope that this is NOT the way the INA20x window comparator works.  I would hope that for the V_UPPER fault the V_IN value would be such that V_{CMP_IN} > (greater than) 0.6V (as just described above) but for the V_LOWER fault V_IN is such that V_{CMP_IN} < (less than) 0.6V.

Thanks,

Eric

Hi Jamaal,
Clearing CMPOUT = HIGH when RESET = HIGH to CMPOUT = LOW will require Vcmpin+ < 0.6 and RESET = LOW (if using the internal 0.6 V reference). This is only applicable to comparator 1. Comparator 2 doesn't have the reset option.
Your understanding is correct regarding the "Comparator Power-on reset". If RESET = HIGH at power up COMPOUT = HIGH and will need RESET = LOW as long as the input is below the limit.
To answer the window comparator question, I need some info. Are you using the 10 pin device or the 14 pin. What are your Vupper limit and Vlower limit and how are you setting it.

Thanks Rabab,

I am using the 10-pin device.  Here is my circuit:

 

The circuitry hanging on the RESET pin just keeps RESET = LO for ~100ms after power up.

 

Here is how I have set V_UPR and V_LWR:

I want V_SNS ~ 200mV (see INA206 data sheet Fig 6).

So I*(Ω)·R_SNS(A) = 0.2V.

                                        For V_UPR choose I* = 3A

R_SNS = 0.2V/3A = 0.067Ω (here I’ve used two 0.13Ω resistors in parallel).

V_SNS = 3A·0.065Ω = 0.195V (almost 200mV).

INA206 has G=20 so G·V_SNS = 3.9V.  This is V_UPR.

Now divide G·V_SNS = 3.9V down to 0.6V.  The 10K-1.82K divider does this.

Fig 41 in the INA206 data sheet associates V_UPR with V_CMP2IN so I’ve connected V_UPR accordingly.  This is how V_UPR becomes V_CMP2IN.

                                        For V_LWR choose I* = 1A

R_SNS = same, of course = 0.067Ω .

V_SNS = 1A·0.065Ω = 0.065V (not even close to 200mV!).

Here G·V_SNS = 1.3V.  This is V_LWR.

Divide G·V_SNS = 1.3V down to 0.6V.  The 10K-8.06K divider does this.

Fig 41 in the INA206 data sheet associates V_LWR with V_CMP1IN so I’ve connected V_LWR accordingly.  This is how V_LWR becomes V_CMP1IN.

Thank you

Hi Jamaal,

I noticed in your schematic that you do not tie the CMP1 and CMP2 outputs together. I do not think you can use them as a wndow comparator without conecting them. You have configured them as separate comparators. These will be the results:

 0<OUTPUT< 1.3 V, CMP1OUT = 0 and CMP2OUT = 1

1.3 V < OUTPUT < 3.9 V, CMP1OUT = 1 and CMP2OUT = 1

OUTPUT > 3.9 V, CMP1OUT = 1 and CMP2OUT = 0

Have you built this prototype?

 

Hi Jamaal,
This is a follow up to the email. As long as Reset is set low, INA206 will work as a window comparator. If the reset is high then it will only work as a upper limit comparator.