SLVAEQ2 April   2020 TPS2549-Q1 , TPS254900-Q1 , TPS254900A-Q1 , TPS2556-Q1 , TPS2557-Q1 , TPS2559-Q1 , TPS25830-Q1 , TPS25831-Q1 , TPS25832-Q1 , TPS25833-Q1 , TPS25840-Q1 , TPS25842-Q1

 

  1.   How to Pass MFi Overcurrent Protection Test With USB Charger and Switch Device
    1.     Trademarks
    2. 1 The Instruction of MFi OCP Requirement
    3. 2 Test Standard and Requirements
    4. 3 The Solution to Pass MFi OCP Test
      1. 3.1 Solution 1: Increasing Current Limit Point Higher Than 1.6*Ia
      2. 3.2 Solution 2: Paralleling RC With Rlimit to Delay the Current Limit Response
        1. 3.2.1 For the 1.5A USB Port With External FET
        2. 3.2.2 For the 1.5A Port Without External FET
        3. 3.2.3 For 2.1A USB Port With External FET
        4. 3.2.4 For 2.1A USB Port Without External FET
        5. 3.2.5 For 2.4A USB Port With External FET
        6. 3.2.6 For 2.4A USB Port Without External FET
        7. 3.2.7 For 3A USB Port With External FET
        8. 3.2.8 For 3A USB Port Without FET
    5. 4 Summary
    6. 5 References

3.2.8 For 3A USB Port Without FET

For 3A USB port, set the current limit to 3.5A without external FET, parallel 11.3kΩ + 82 nF RC with 11.3kΩ Rlimit. The Vcsn drop is 4.02 V under the certification load.

figure 21.tifFigure 18. Set 3.5A Current Limit for 3A Port Without External FET

According to above test results, solution 2 can be summarized as shown in Table 5.

Table 5. Summary of Solution 2

Solution and Result With External FET-- Rlimit//(Rpara+Cpara) Without External FET--Rlimit//(Rpara+Cpara)
1.5A port (1.8A current limit) 10.7kΩ//(10.7kΩ + 82nF) Result: Vbus no drop 21.5kΩ//(21.5KΩ + 82nF) Result : Vcsn no drop
2.1A port (2.52A current limit) 7.68kΩ//(7.68kΩ + 82nF) Result: Vbus no drop 15.8kΩ//(15.8kΩ + 82nF) Result: Vcsn no drop
2.4A port (2.88A current limit) 6.65kΩ//(6.65kΩ + 82nF) Result: Vbus no drop 13.7kΩ//(13.7kΩ + 82nF) Result: Vcsn no drop
3A port (3.5A current limit) 5.45kΩ//(3.5kΩ + 220nF) add 330 µf on CSP Result: Vbus drop to 3.96V 11.3kΩ//(11.3kΩ + 82nF) add 330 µf on CSP Result: Vcsn drop to 4.02 V