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TDFN33-12 Datasheet(PDF) 10 Page - Skyworks Solutions Inc. |
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TDFN33-12 Datasheet(HTML) 10 Page - Skyworks Solutions Inc. |
10 / 17 page AAT4685 Over-Voltage Protection Switch with OCP and BOVP DATA SHEET 10 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com 201960A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 16, 2012 Under-Voltage Lockout (UVLO) The AAT4685 has a fixed 2.7V under-voltage lockout level (UVLO) trip level for IN rising. When the input volt- age is less than 2.7V - VUVLO_HYS, the OVP switch is turned off. 100mV of hysteresis is included to ensure circuit stability. Over-Voltage Protection (OVP) The AAT4685 adjustable version has a 1.0V ± 3% over- voltage trip threshold on the OVP pin. With a resistor divider on OVP pin from IN to GND, the over-voltage protection point of IN can be adjusted between 4V and 7V. If the over-voltage trip level is triggered, the OVP switch will start to be turned off in 1μs. The FLT pin is driven low. When the input voltage pin returns below VOVPT – VOVP_HYS (but is still above VUVLO), the OVP switch is turned on again after a TOVP_REC recovery time to ensure that the input supply has stabilized. Fixed OVP products are also available where the resistive divider is internally integrated. Pin 12 is designed to be not connected. Over-Current Protection (OCP) The AAT4685 integrates adjustable over-current protec- tion. Once the load current exceeds the pre-set limit of IOCP current (ILOAD>IOCP), the load current is limited after the OCP blanking time (typical 180μs). During the OCP blanking time, the OVP switch stays ON. Once the load current drops below IOCP, current restriction will be removed. If the over-current state continues after the blanking period, the OVP switch turns off and FLT is pulled down. In order to prevent the input voltage from spiking up due to the inductance of the input cable, the OVP switch is turned off slowly, resulting in a "soft-stop." The OVP switch will turn back on again after TOCP_REC (typical 64ms) and the current is monitored all over again. Each time an OCP fault occurs, an internal counter is incremented. If 15 OCP faults occur in one charge cycle, the OVP switch is turned off permanently. The counter is cleared either by removing and re-applying input power, or by disabling and re-enabling the device via the EN pin. The OCP threshold is set by an external resistor (ROCP) connected between OCP and ground. IOCP is approxi- mated by the following formula: I OCP = (current in A, resistance in kΩ) 30 R OCP Battery Over-Voltage Protection (BOVP) The AAT4685 monitors the positive battery terminal and turns the OVP switch off when the battery voltage exceeds the BOVP threshold (typical 4.35V). The monitor has blanking time TBOVP_BL (typical 180μs) to prevent any transient voltage from false triggering the BOVP. A resis- tor is required between the BOVP pin and the battery, to limit the current in case of a short circuit condition. If the battery voltage exceeds the BOVP trip threshold VBOVPT, the OVP switch is turned off, and the FLT pin is driven low. In order to prevent the input voltage from spiking up due to the inductance of the input cable, the OVP switch is turned off slowly , resulting in a "soft-stop." The OVP switch is turned back on once the battery voltage drops to VBOVPT – VBOVP_HYS. Each time a battery over- voltage fault occurs, an internal counter is incremented. If 15 such faults occur in one charge cycle, the OVP switch is turned off permanently. The counter is cleared either by removing and re-applying input power, or by disabling and re-enabling the device via the EN pin. Over-Temperature Protection (OT Protection) If the junction temperature of the device exceeds TSHDN, the OVP switch is turned off, and the FLT pin is driven low. The OVP switch is turned back on when the junction temperature falls below TSHDN - 15°C. Fault Indicator (FLT) The FLT output is an active-low open-drain fault (OV/OC/ BOVP/OT) reporting output. A pull-up resistor should be connected from FLT to the logic I/O voltage of the host system. When EN is low, FLT is asserted by pulling down in the case of an over-voltage, over-current, or battery over-voltage or over-temperature fault occuring; FLT is de-asserted into high impedance state with the fault removed. When EN is high, FLT is in high impedance status. |
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Descripción similar - TDFN33-12 |
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