[Elphel-support] FW: Spawar Systems Center; ADIS16375; current draw

Thu Nov 17 16:31:24 PST 2011

Hi Andrey,

Here is the correspondence that we've had with Analog Devices. It appears
that our ADIS has been damaged - probably from the first 6.3V we applied.
So, should we send it to you along with the camera/IMU board, or should you
use your own IMU?

Remember that the voltage in the 103695 is still strange - 4.3V unloaded,
3.6V loaded - so I do not believe our problem is the ADIS. At least, not the
whole problem. So its still worthwhile to have the 103695 repaired.

We'll try to get Analog Devices to repair the ADIS, but we might need to buy
a new one. Either option will take a few weeks I think. I'd rather get you
the 103695 board now, rather than later.

I'm out until Monday. I'll try to ship things to you then.

Lee 

-----Original Message-----
From: Looney, Mark [mailto:Mark.Looney at analog.com] 
Sent: Thursday, November 17, 2011 2:37 PM
To: Gorgen, Justin E CIV SPAWARSYSCEN-PACIFIC, 52340; Lemay, Lee C CIV
SPAWARSYSCEN-PACIFIC, 52340
Subject: RE: Spawar Systems Center; ADIS16375; current draw

Hello Justin,

At this point, I am not sure.  It sounds like sneak path for 400mA of
current.  If this were resistive, this might make sense.  As the voltage
increases, the real current required by the ADIS16375 will go down, due to
the internal power regulator and the resistive part will go up.  That would
explain little or no current change over the supplies. May want to check the
supply at the pins, because the ADIS16375 will actually start working at
2.85V, if the supply is solid (and the transient doesn't cause it to droop).

Let me get with the Design Engineer and get back to you.  I am out until
Tuesday so it may take 2-3 days.

Best,
Mark

Mark Looney
iSensor Application Engineer
Analog Devices, Inc.

-----Original Message-----
From: Gorgen, Justin E CIV SPAWARSYSCEN-PACIFIC, 52340
[mailto:justin.gorgen at navy.mil]
Sent: Thursday, November 17, 2011 5:25 PM
To: Looney, Mark; Lemay, Lee C CIV SPAWARSYSCEN-PACIFIC, 52340
Subject: RE: Spawar Systems Center; ADIS16375; current draw

Hi Mark,

Yes, 600 mA is the steady current. We tested this by putting the ADIS16375
on the PCBZ and supplying voltage to it with a labratory dc power supply
with a current meter in series with the PCBZ.

The power supply reports load current, which agrees with the current meter's
readings, so this probably isn't a calibration issue with our lab equipment.
Also, the PCBZ without an ADIS plugged in draws no current, so our PCBZ does
not have a short..

The behavior we observed from the ADIS16375 is as follows.

1.  Starting from no power, we set the voltage on VDD to 3.0 Volts, at which
point the ADIS draws 400 mA from VDD.  At this point, the ADIS is not on (
it does not respond to SPI ).

2. We ramp the voltage VDD upwards from 3.0 volts to 3.4 volts.

3. The ADIS16375 doesn't start ( does not respond to SPI commands) until VDD
reaches 3.35 Volts, at which point current jumps from 400mA to 600mA and the
ADIS will now respond to SPI.

4. Now that the ADIS is awake, We ramp VDD down from 3.4 volts to 3.0 volts,
the ADIS draws 600mA from VDD at all voltages between 3.0 and 3.4 Volts. It
continues to respond to SPI at these VDD voltages, and continues to draw
600mA.

Plugging the ADIS16375 into the USBZ, we can no longer observe the current
draw, but the VDD is at 3.28 volts. All status registers, when viewed with
the Analog Devices software, are normal. The accelerometer and gyro values
being read from the ADIS16375 appear to be accurate.

What are your thoughts, Mark?

Thanks for your time.
Sincerely,
Justin Gorgen

________________________________

From: Looney, Mark [mailto:Mark.Looney at analog.com]
Sent: Thu 11/17/2011 1:04 PM
To: Lemay, Lee C CIV SPAWARSYSCEN-PACIFIC, 52340
Cc: Gorgen, Justin E CIV SPAWARSYSCEN-PACIFIC, 52340
Subject: Spawar Systems Center; ADIS16375; current draw

Hello Lee,

Is that steady current?  The ADIS16375 does have a large transient current
at start-up, which can ready 1.5A for 400us, but should not be drawing that
sort of current by itself.  Where are you measuring this current?

Regards,
Mark

Mark Looney
iSensor Application Engineer
Analog Devices, Inc.

-----Original Message-----
From: Lemay, Lee C CIV SPAWARSYSCEN-PACIFIC, 52340
[mailto:lee.lemay at navy.mil]
Sent: Thursday, November 17, 2011 2:45 PM
To: Looney, Mark
Cc: Gorgen, Justin E CIV SPAWARSYSCEN-PACIFIC, 52340
Subject: Spawar Systems Center; ADIS16375; current draw

Hi Mark,

We're using an ADIS 16375. It appears to function correctly when we
interface to it with ADISUSBZ. However, we are concerned because it draws
600 mA of current under normal operation. This is above the rated 173 mA
from the spec sheet. Should we be concerned, and do you have any
recommendations about how we can fix this or replace the unit?

I appreciate your time and help!

Best Regards,
Lee Lemay
Engineer
Spawar Systems Center,  San Diego
53560 Hull Street
San Diego, Ca.
92152
(619)553-8619

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