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UCC2975PW Datasheet(PDF) 8 Page - Texas Instruments |
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UCC2975PW Datasheet(HTML) 8 Page - Texas Instruments |
8 / 28 page UCC2975, UCC2976, UCC2977 UCC3975, UCC3976, UCC3977 SLUS499A – NOVEMBER 2001 – REVISED JANUARY 2002 8 www.ti.com state diagram A logic state diagram for the UCC397x family of controllers is shown in Figure 5. During power-up the controller transitions from UVLO to the momentary startup state. During startup, the COMP pin is preconditioned at maximum frequency and the OPEN/SD capacitor is discharged before beginning normal operation. In the normal operating state, the frequency is swept from high to low allowing the lamp to be struck and the current in the lamp to be regulated. STARTUP * OPEN/SD = 0V COMP = 0V OSC, OUT active NORMAL OPERATION OPEN/SD < 1.5V COMP < 2.5V OSC, OUT active OPEN LAMP * 1.5V < OPEN/SD <2.5V COMP < 2.5V OSC, OUT active NO–LOCK * COMP > 2.5V OPEN/SD < 1.5V OSC, OUT active COUNT=7? ERROR SHUTDOWN OSC active OUT off state UVLO VDD < 3.0V OSC inactive OUT off state COUNT=0 SHUTDOWN OPEN/SD > 2.5V COUNT =0 OSC inactive OUT off state Low current VDD, OPEN/SD VDD>3.0V OPEN/SD < 0.5V NO YES Increment COUNT OUT off state UCC3975: OUT1 low, OUT2 low UCC3976: OUTP high, OUTN high UCC3977: OUT1 low, OUT2 low * Momentary states UDG–01102 Figure 5. State Diagram The normal operating state can be exited in one of four ways: • bringing V DD < 3 V • a user commanded shutdown (OPEN/SD > 2.5 V) • an open lamp condition (OPEN/SD > 1.5 V), or • if the device fails to achieve regulation before reaching minimum frequency (EAO > 2.5 V). The latter two conditions cause an internal retry counter to increment before attempting another startup. If the application does not operate normally after seven retrys, the controller enters an error induced shutdown state removing power to the load. The error state and counter can be cleared by removing VDD to the part or by a user commanded shutdown. |
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