Texas Instruments TPS25921XEVM-637, User Manual

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General Configurations
4.3.1.2 For CH2 (J5)
Use the following steps to test CH2 (J5).
1. Press the EVM RST switch, S2 and verify that the voltage at VOUT2 (TP16) starts falling slowly below
12 V and the red FLTb2 LED (D7) turns ON. Release S2.
2. Reduce the input voltage on VIN2 and monitor VOUT2. Verify that VOUT2 (TP16) starts falling and is
fully turned off when VIN2 (TP15) reaches 4.2 V (±0.3 V). Verify that FLTb2 red LED (D7) turns ON.
3. Adjust the power supply voltage to 12 V.
4. Increase the input voltage on VIN2 and monitor VOUT2. Verify that VOUT2 (TP16) starts increasing
and then turns off when VIN2 (TP19) exceeds 17 V (±1 V). Verify that the FLTb2 red LED (D7) turns
ON.
5. Adjust the power supply voltage to 12 V.
6. Turn off the power supply.
4.3.1.3 Current Limit Test
Use the following steps to conduct the current limit test.
1. Verify all three current limits (CH1 and CH2, with only 1 channel powered at a time) and verify the latch
and auto-retry feature. Setup the oscilloscope as shown in Table 8 .
Table 8. PWR637 Oscilloscope Setting for Current Limit Test
(1) (2)
Oscilloscope Setting CH1 Probe Points CH2 Probe Points
Channel 1 = 5 V/div TP5 = VOUT1 TP18 = VOUT2
Channel 2 = 5 V/div TP6 = VIN1 TP19 = VIN2
Channel 4 = 1 A/div Input current into J1 +ve wire Input current into J5 +ve wire
Trigger source = Channel 4
Trigger level = 0.6 A ±0.1 A
Trigger polarity = +ve
Trigger mode = Single sequence
Time base 200 ms/div 40 ms/div
(1)
If an electronic load is used, ensure that the output load is set to constant resistance mode and not constant current mode.
(2)
Measuring current limit values on the oscilloscope can easily cause 8% error from anticipated values listed in Table 8.
2. The jumper setting for the different current limit test is shown in Table 9 .
Table 9. PWR637 Jumper Settings for Current Limits
Jumper Position
Load Current Limit
J3 (CH1) J7 (CH2)
2-3 2-3 1.0 A ±0.08 A
1-2 1-2 0.5 A ±0.04 A
No jumper No jumper 1.50 A ±0.12 A
3. Set the output load at 5.0 Ω ±0.5 Ω on CH1 and then enable the load. Turn on the VIN1 power supply
and verify that input current is limited, as per the setting in the Table 9 . Verify the device is in auto-retry
mode and that the FLTb1 RED LED (D3) turns on and off as shown in Figure 3 . The level of the
current pulse should match with the load current limit (based on the respective jumper setting), as
shown in
Table 9 .
9 SLUUB50 – August 2014 TPS25921X-637EVM: Evaluation Module for TPS25921X
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