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TS3A24159

eli
Guru 13485 points
Other Parts Discussed in Thread: TS3A24159

using the TS3A24159YZPR device in my design and I have a question regarding it's current consumption:

During regular tests I noticed that the device current consumption is by far larger than expected (I performed measurements at 2 devices).

At 25deg I measured 145nA and 147nA.

At 80deg I measured 1.966uA and 2.028uA.

 

After I noticed that current consumption is larger than expected I made sure that no other device is related to that current consumption by disconnecting series resistors. follwing are the results:

T = -20deg:  i=6nA

T = 0deg;     i=24nA

T = 25deg;   i=145nA

T = 40deg;   i=332nA

T = 50deg;   i=554nA

T = 60deg;   i=888nA

T = 70deg;   i=1362nA

T = 80deg;   i=2026nA

 

After this test I made another test; this time I made sure that all NC and NO inputs are tied to GND or VCC.

However, I got the same current consumption.

 

Vcc during the tests is 2.75V

 

Current was measured with Agilent N6705B DC power analyzer (N6781A module).

  • 0
    TI__Mastermind 45605 points

    Eli,

    The data you provided appears to be higher current consumption we expect with a 2.7 V supply according to the datasheet.  We do expect the current consumption to increase with temperature as you show but we shouldn't see it going over 100nA at 25 deg C.  I have looked at some of our historical  characterization data and it looks well within spec of 700nA across temperature. 

    What are your input logic pin Voltage when taking your data?

    How many units are you seeing this higher current consumption?

    Thank you,

    Adam

  • 0 in reply to Adam Torma
    Guru 13485 points

    Adam,

    I performed further tests with different units and the results are very similar.

    According to my measurements, the results are more or less the same regardsless of the NCx and NOx state.

    However, in order to make sure I performes an additional test with the following conditions:

    IN2, NC2, NO2 = GND

    COM2 = open

    IN1, NC1 = GND

    NO1 = VCC through 10K resistor pull up

     

    In all tests COM1 was connected directly to the Enable input of AP2280-2FMG-7 load switch manufactured by DIODES INC.

    It appears that this input does not consumes large amount of current; At 80deg the total current consumption increased at 20nA when I changed IN1 from low to high (in this condition NO1 which is pulled high through 10K resistor is connected to the load switch Enable input).

     

    To summerize the issue, I performed the tests at 4 units, at all tests the INx inputs were defined correctly (VCC or 0V) and the NCx/NOx terminals were at different positions. At all tests the current consumption at 25 deg was 135nA-145nA and at 80 deg it was 1870nA-2026nA.

     

  • 0 in reply to eli
    TI__Mastermind 45605 points
    Eli,

    What do you think about next steps?

    I was thinking of trying to duplicate your experiment in my bench to see if I get similar results.

    What equipment are you using to measure the current consumption on the Vcc pin of the TS3A24159?

    Adam
  • 0 in reply to Adam Torma
    Guru 13485 points

    Hi

    My PCB contains a series resistor at the VCC pin of TS3A24159.

    I disconnected that resistor and used Agilent N6781A module (installed insidw Agilent N6705B equipment) to measure the current.

    The measurement range was adjusted to the minimum (10uA).

     

    As I described earlier, my PCB allow me to define INx, NOx, NCx as '0' or '1';

    COM2 is open.

    COM1 is connected directly to the Enable input of a load switch device (DIODES INC. AP2280-2FMG-7).

  • 0
    TI__Mastermind 45605 points

    Eli,

    Update:

    1)I did a quick bench set up to test the Icc spec per the datasheet to get a baseline for my proceedings. With Vcc= 3.3V and all other pins open I recorded Icc = 16 nA.

    2) I tried to duplicate your set up

    IN2, NC2, NO2 = GND

    COM2 = open

    IN1, NC1 = GND

    NO1 = VCC through 10K resistor pull up

    I measured 252nA in this configuration.  This is saying to me that there are leakage paths from Vcc to ground through the internal switches.  If you leave the switches open there is no leakage path for the Vcc to ground through the internal switches.

    3) I tried to create the most leakage I could from Vcc to GND by grounding all the signal paths and was able to get Icc up to 272nA. 

    4) I proved this leakage concept to myself by setting Vcc= 3.3V, IN1/2 = 0V, and left NC1/2 NO1/2 signal paths floating.  I toggled COM1/2 from 3.3V to 0V.  

    If COM1/2 = 0V, Icc = 229nA

    If COM 1/2 = 3.3V, Icc = 14nA


    This tells me that the potential difference across the internal switches from Vcc to GND can cause some leakage.

    Let me know if this explains what you are seeing in your testing. 

    Thank you,
    Adam

  • 0 in reply to Adam Torma
    Guru 13485 points

    After some further investigation it appears that the extra current consumption is drawn from NO1 pin which is connected to the VCC pin through a 10K resistor.

     

    After discovering this I made some further tests as described below:

    VCC = 2.75V

    Vin = GND

    V_COM = open

    V_NC = GND

    Voltage at NO1 pin was supllied by a separated  external supply while monitoring the current into this pin.

     

    NO1 voltage was increased and the input current to that pin was monitored.

     

    I found out that as long as the NO1 voltage is 2.6V or less, the NO1 leakage current is more or less constant (below 30nA).

    As the voltage approached 2.7V the current dramatically increased and when the NO1 voltage was 2.75V (same as VCC) the leakage current approaced 110nA.

     

    I got similar results regardless the IN input status (GND or VCC).

     

    The Vcc current during these tests was also monitored and was stable (7nA - 9nA).

     

    At 80deg the behaviour was similar but the currents were much higher (455nA at V_NO1=1V, 573nA at V_NO1=2.4V, 922nA at V_NO1=2.7V, 2.2uA at V_NO1=2.75V).

     

    I noticed that in datasheet the leakage current is given for V_NO or V_NC equal or less than 2.2V; is there a special reason for that?

    What is the cause of this dramatic increase of the leakage current when V_NO approaches VCC?

     

  • 0 in reply to eli
    Guru 13485 points

    Hi Adam

    Any feedback?

    B.regards

    Eli

  • 0 in reply to eli
    TI__Mastermind 45605 points

    Eli,

    Thank you for bringing this back up to my attention.  

    I noticed that in datasheet the leakage current is given for V_NO or V_NC equal or less than 2.2V; is there a special reason for that?

    Based on your experiments it sounds like the behavior is expected since the device is operating within the datasheet limits so I have put in a request to the design team to identify and explain the leakage mechanism that causes the increase in leakage as the input/output signal gets close to the supply.