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TPS22950: Current much higher than current limit setting

Part Number: TPS22950

Tool/software:

Hello there,

 I am testing the current limiting of the TPS22950YBHR.

 From the datasheet, it has an ILIM range that goes down to 50 mA.

 For the test, I have an electronic load hooked up to the VOUT pin of the TPS22950 and have VIN connected to 3.3 V.  The RILIM is set to 19.1K which should set the ILIM to 50 mA.  I have the TPS22950 enabled and am sinking various load currents.

 I started with 10 mA and increased by 10 mA each step expecting it to start limiting at 50 mA, but it went to 230 mA before it started limiting.  When it tripped at 230 mA, it then limited the current to 50 mA.

Load (mA)

Vout (V)

0

3.30

12

3.26

20

3.23

30

3.20

40

3.17

50

3.14

60

3.11

70

3.08

80

3.05

90

3.02

100

2.99

110

2.95

120

2.92

130

2.89

140

2.86

150

2.83

160

2.80

170

2.77

180

2.73

190

2.70

200

2.67

210

2.63

220

2.60

230

0.002

 Am I doing something wrong, or is this how the part is designed to perform?

Thanks!

  • Hi Gregory,

    Is it possible for you to test this again with CR mode of e-load. It looks like the above was tested using CC mode. You can set the load resistance as Vin/I_load. 

    Please let me know the findings from this.

    Best Regards,
    Arush

  • I did that too and it had results similar to constant current.  Here they are.  The voltage reading is from the e-load.

    Enable TPS22950, then enable e-load and vary resistance.  The results were the same whether the e-load was enabled or not when adjusting the resistance.

    Resistance (Ohms)

    Current (mA)

    Voltage (V)

    30

    99

    2.98

    15

    182

    2.72

    14

    192

    2.69

    13

    204

    2.65

    12

    217

    2.60

    11

    113

    1.4

    10

    95

    1.1

    9

    84

    0.92

    8

    58

    0.52

    7

    55

    0.41

    6

    54

    0.31

    5

    55

    0.27

    4

    55

    0.22

    3

    55

    0.17

    2

    55

    0.12

    1

    55

    0.06

     

    Enable e-load using constant resistance, then enable TPS22950.

    Resistance (Ohms)

    Current (mA)

    Voltage (V)

    15

    182

    2.72

    10

    100

    1.25

    5

    55

    0.27

  • Any update on this issue?  It has been 5 days since I replied.

  • Hi Gregory,

    Thank you for the reminder,

    It looks like there is some issue with the setup. I see that the for Rload = 1ohm to 8 ohms, the device is limiting the current.

    Can you verify your setup once. Check all the limits (voltage and current) for input supply and load. EVM setup. Check if Vin is dropping when testing.

    Vout is following ILIM*Rload for all the entries in the above table so it looks like somehow current is being limited but I am not sure if it is done by device or by some equipment.

    Best Regards,
    Arush

  • The test setup looks okay.  Could this issue be related to: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1322214/tps22950-behaviour-not-as-expected?tisearch=e2e-sitesearch&keymatch=TPS22950

    The difference seems to be that in that case they stopped at 100 mA.  Could this be the same issue I am seeing, but in my case it goes up to 220 mA before the over-current protection activates?

    Thanks!

  • Hi Gregory,

    Thank you for pointing this out.

    I personally don't think this is due to ILIM inaccuracy. We have this in datasheet specs.

    This is the final current limit threshold. I might be that trigger threshold is slightly higher for low current application and requiring this high load for device to limit the current at correct threshold. 

    I am checking further on this. Please expect some delays due to holidays this week. 

    Best Regards,
    Arush