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UC1904 Scheda tecnica(PDF) 4 Page - Texas Instruments |
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UC1904 Scheda tecnica(HTML) 4 Page - Texas Instruments |
4 / 7 page PIN FUNCTIONAL DESCRIPTION 2.5V: This is the output of the precision 2.5V reference. ARST Input: This input, with a 4:1 hysteretic threshold, is used to sequence a power system through the Auto ReStarT cycle. A delayed representation of a supply out- put voltage is used at this pin to provide adequate startup time for the power system, and a minimum power-off pe- riod. Gnd: Reference point for the internal reference and all thresholds, as well as the return for the remainder of the device. LS Input: The Line Sense input is used to monitor a volt- age that varies with the input line voltage to a system. The input is compared to a precision 2.0V level and is used to activate the PWRW and PG outputs, as well as triggering the Auto Restart sequence. OC Input: The Over-Current input can be used to re- spond to an inverted over-current signal. A low level sig- nal at this input latches in a fault indication at the OV/OC output. OFF DLY: This pin functions similarly to the POR DLY pin to delay the turn-on of the ON/OFF output transistor. The charging current and upper threshold are 12 µA and 2.1V. ON/OFF Input: With a high level at this input the ON/OFF Out pin is activated after a user-programmable delay. A high level also activates the PG Out pin, and re- sets the OV/OC fault latch. On/Off Out: This output is an open collector output that is activated by the ON/OFF Input, or the Auto Restart cir- cuitry. Saturation voltage on this and all the open collec- tor outputs is rated at 10mA of current. OV/OC Out: In response to either an Over-Voltage or Over-Current situation this output is latched active low. There is nominal 20 µs delay in the OV path to the fault latch, providing rejection to transient overshooting on the monitored voltages. The low condition is cleared when the fault latch is reset by the ON/OFF Input, or a UVLO condition on the device. POR DLY: This pin is used, with an external capacitor, to program a Power-On-Reset delay. This delay is reset whenever there is a UV condition at one of the S1-S4 in- puts, and then triggered upon the clearing of the UV con- dition. When reset, the voltage across the capacitor is quickly discharged to near zero volts, and the PG Out pin goes active low. Once triggered the capacitor is charged by a 9 µA current source. The PG Out pin remains active low until the delay capacitor voltage reaches a 2.1V threshold. PG Out: During any fault, under-voltage, or UVLO condi- tion this output is low. A Power Good indication (output off) is given when all supply conditions are within defined operating limits. During power-up the PG signal is de- layed by a programmable Power On Reset delay. During UVLO the output is active low as long as the input sup- ply, VIN, is above approximately 1.0V. PWRW Out: When a low line condition is sensed by the LS Input this output goes low. This output is disabled (off) during a UVLO condition. S1-S4: These are the sense inputs for OV and UV moni- toring of external voltages. All four inputs can be used to sense positive voltages with a simple divider to scale the voltage level to the 2.5V centered window. The S3 and S4 inputs can also be used to sense -12V and -5V sup- plies respectively with no external components. This is done with internal precision resistor dividers and two source only op-amps that are disabled when the pins are used in the positive mode. VIN: Input supply for the UC1904. The device is opera- tional with 4.75V to 18V on this pin. WADJ: The WADJ input is used to program the OV and UV window thresholds. The OV-UV window is centered around the 2.5V reference and is nominally ±20% per volt on the WADJ input pin. UC1904 UC2904 UC3904 4 |
Codice articolo simile - UC1904_08 |
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Descrizione simile - UC1904_08 |
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