Electronic Components Datasheet Search |
|
ISL6504ACB-T Datasheet(PDF) 10 Page - Intersil Corporation |
|
ISL6504ACB-T Datasheet(HTML) 10 Page - Intersil Corporation |
10 / 16 page 10 FN9062.2 April 13, 2004 During sleep-to-active state transitions from conditions where the 5VDUAL output is initially 0V (such as S5 to S0 transition, or simple power-up sequence directly into active state), the circuit goes through a quasi soft-start, the 5VDUAL output being pulled high through the body diode of the N-Channel MOSFET connected between it and the 5V ATX. Figure 9 exemplifies this start-up case. 5VSB is already present when the main ATX outputs are turned on, at time T0. As a result of +5VIN ramping up, the 5VDUAL output capacitors charge up through the body diode of Q4 (see Typical Application). At time T1, all main ATX outputs exceed the ISL6504/A’s undervoltage thresholds, and the internal 25ms (typical) timer is initiated. At T2, the time-out initiates a soft-start, and the 1.2V voltage ID output is ramped-up, reaching regulation limits at time T3. Simultaneous with the beginning of this ramp-up, at time T2, the DLA pin is released, allowing the pull-up resistor to turn on Q2 and Q4, and bring the 5VDUAL output in regulation. Shortly after time T3, as the SS voltage reaches 2.75V, the soft-start capacitor is quickly discharged down to approximately 2.45V, where it remains until a valid sleep state request is received from the system. Fault Protection All the outputs are monitored against undervoltage events. A severe overcurrent caused by a failed load on any of the outputs, would, in turn, cause that specific output to suddenly drop. If any of the output voltages drops below 80% (typical) of their set value, such event is reported by having the FAULT pin pulled to 5V. Additionally, exceeding the maximum current rating of an integrated regulator (output with pass regulator on chip) can lead to output voltage drooping; if excessive, this droop can ultimately trip the undervoltage detector and send a FAULT signal to the computer system. A FAULT condition occurring on an output when controlled through an external pass transistor will only set off the FAULT flag, and it will not shut off or latch off any part of the circuit. A FAULT condition occurring on an output controlled through an internal pass transistor, will set off the FAULT flag, and it will shut off the respective faulting regulator only. If shutdown or latch off of the entire circuit is desired in case of a fault, regardless of the cause, this can be achieved by externally pulling or latching the SS pin low. Pulling the SS pin low will also force the FAULT pin to go low and reset any internally latched-off output. Special consideration is given to the initial start-up sequence. If, following a 5VSB POR event, any of the 1.5VSB or 3.3VDUAL/3.3VSB outputs is ramped up and is subject to an undervoltage event before the end of the second soft-start ramp, then the FAULT output goes high and the entire IC latches off. Latch-off condition can be reset by cycling the bias power (5VSB). Undervoltage events on the 1.5VSB and the 3.3VDUAL/3.3VSB outputs at any other times are handled according to the description found in the second paragraph under the current heading. Another condition that could set off the FAULT flag is chip overtemperature. If the ISL6504/A reaches an internal temperature of 140oC (typical), the FAULT flag is set, but the chip continues to operate until the temperature reaches 155oC (typical), when unconditional shutdown of all outputs takes place. Operation resumes only after powering down the IC (to create a 5VSB POR event) and a start-up (assuming the cause of the fault has been removed; if not, as it heats up again, it will repeat the FAULT cycle). In ISL6504/A applications, loss of the active ATX output (3.3VIN; as detected by the on-board voltage monitor) during active state operation causes the chip to switch to S5 sleep state, in addition to reporting the input UV condition on the FAULT pin. Exiting from this forced S5 state can only be achieved by returning the faulting input voltage above its UV threshold, by resetting the chip through removal of 5VSB bias voltage, or by bringing the SS pin at a potential lower than 0.8V. Application Guidelines Soft-Start Interval The 5VSB output of a typical ATX supply is capable of 725mA, with newer models rated for 1.0A, and even 2.0A. During power-up in a sleep state, the 5VSB ATX output needs to provide sufficient current to charge up all the applicable output capacitors and, simultaneously, provide some amount of current to the output loads. Drawing FIGURE 9. SOFT-START INTERVAL IN ACTIVE STATE 0V 0V TIME OUTPUT (1V/DIV) VOLTAGES T1 T2 T3 T0 INPUT VOLTAGES (2V/DIV) +5VIN +12VIN +5VSB VOUT1 (1.5VSB) VOUT3 (3.3VDUAL/3.3VSB) VOUT4 (5VDUAL) DLA PIN (2V/DIV) +3.3VIN VOUT2 (1.2VVID) SOFT-START (1V/DIV) ISL6504, ISL6504A |
Similar Part No. - ISL6504ACB-T |
|
Similar Description - ISL6504ACB-T |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |