AT9933DB1
(a): rise time
(b): fall time
Fig. 9. PWM Dimming rise and fall times
Channel 1 (blue): PWM Dimming Input Signal (2V/div)
Channel 4 (Green): LED current (100mA/div)
Conducted EMI Tests on the AT9933DB1
In preliminary tests conducted on the demo board, the board and the maximum conducted EMI obtained from measure-
meets SAE J1113 Class 3 conducted EMI standards without ments on the board. The table also lists the Class of the SAE
the need for any input filters (other than the input capacitors standard the board meets in each frequency range.
already included). This is a result of the combination of the
continuous input current and a localized switching loop (Q1 The conducted EMI plots for the HV9930DB1 obtained at
– C1 – D3).
an input voltage of 13.5V and an LED string voltage of 27V
(output current is 350mA) are given in the Appendix.
Table 1 details the conducted EMI limit as per SAE J1113
Table 1. Conducted EMI Measurements
Conducted EMI Limit for
Conducted EMI by
Class as per SAE J1113
AT9933DB1
Frequency Range
Class 3
150kHz - 300kHz
530kHz - 2.0MHz
5.9MHz - 6.2MHz
30MHz - 54MHz
70MHz - 108MHz
70 dBµV (narrowband)
50 dBµV (narrowband)
45 dbµV (narrowband)
65 dbµV (broadband)
49 dbµV (broadband)
40 dBµV
48 dBµV
29 dBµV
54 dBµV
47 dBµV
Class 5
Class 3
Class 5
Class 4
Class 3
6
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