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AP2552W6-7 Datasheet(PDF) 9 Page - Diodes Incorporated |
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AP2552W6-7 Datasheet(HTML) 9 Page - Diodes Incorporated |
9 / 16 page AP2552/AP2553/AP2552A/AP2553A Document number: DS35404 Rev. 5 - 2 9 of 16 www.diodes.com December 2012 © Diodes Incorporated AP2552/ AP2553/ AP2552A/ AP2553A Application Note The AP2552/53 AND AP2552A/53A are integrated high-side power switches optimized for Universal Serial Bus (USB) that requires protection functions. The power switches are equipped with a driver that controls the gate voltage and incorporates slew-rate limitation. This, along with the various protection features and special functions, makes these power switches ideal for hot-swap or hot-plug applications. Protection Features: Under-Voltage Lockout (UVLO) Whenever the input voltage falls below UVLO threshold (~2.5V), the power switch is turned off. This facilitates the design of hot-insertion systems where it is not possible to turn off the power switch before input power is removed. Over-Current and Short-Circuit Protection An internal sensing FET is employed to check for over-current conditions. Unlike current-sense resistors, sense FETs do not increase the series resistance of the current path. When an overcurrent condition is detected, the device maintains a constant output current and reduces the output voltage accordingly. Complete shutdown occurs only if the fault stays long enough to activate thermal limiting. The different overload conditions and the corresponding response of the AP2552/53 AND AP2552A/53A are outlined below: S.NO Conditions Explanation Behavior of the AP2552/53 AND AP2552A/53A 1 Short-circuit condition at start-up Output is shorted before input voltage is applied or before the part is enabled The IC senses the short circuit and immediately clamps output current to a certain safe level namely ISHORT. 2 Short-circuit or overcurrent condition Short-Circuit or Overload condition that occurs when the part is enabled. • At the instance the overload occurs, higher current may flow for a very short period of time before the current limit function can react. • After the current limit function has tripped (reached the over- current trip threshold), the device switches into current limiting mode and the current is clamped at ISHORT /ILIMIT. 3 Gradual increase from nominal operating current to ILIMIT Load increases gradually until the current-limit threshold.(ITRIG) The current rises until ILIMIT or thermal limit. Once the threshold has been reached, the device switches into its current limiting mode and is set at ILIMIT. Note that when the output has been shorted to GND at extremely low temperature (< -30°C), a minimum 120- μF electrolytic capacitor on the output pin is recommended. A correct capacitor type with capacitor voltage rating and temperature characteristics must be properly chosen so that capacitance value does not drop too low at the extremely low temperature operation. A recommended capacitor should have temperature characteristics of less than 10% variation of capacitance change when operated at extremely low temp. Our recommended aluminum electrolytic capacitor type is Panasonic FC series. Current-Limit Threshold Programming The current-limit threshold can be programmed using an external resistor. The current-limit threshold is proportional to the current sourced out of ILIM. The recommended 1% resistor range for RLIM is 10kΩ ≤RLIM≤210kΩ. Figure 15 includes current-limit tolerance due to variations caused by temperature and process. This graph does not include the external resistor tolerance. The traces routing the RLIM resistor to the AP2552/53 and AP2552A/53A should be as short as possible to reduce parasitic effects on the current-limit accuracy. To design below a maximum current-limit threshold, find the intersection of RLIM and the maximum desired load current on the IOS(max) (ILIM) curve and choose a value of RLIM above this value. Programming the current limit below a maximum threshold is important to avoid current limiting upstream power supplies causing the input voltage bus to droop. The resulting minimum current-limit threshold is the intersection of the selected value of RLIM and the IOS(min) (ILIM) curve. |
Similar Part No. - AP2552W6-7 |
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Similar Description - AP2552W6-7 |
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