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TS2026CS bảng dữ liệu(PDF) 5 Page - Taiwan Semiconductor Company, Ltd |
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TS2026CS bảng dữ liệu(HTML) 5 Page - Taiwan Semiconductor Company, Ltd |
5 / 7 page TS2026 5-7 2005/11 rev. A Function Description Input and Output IN is the power supply connection to the logic circuitry and the drain of the output MOSFET. OUT is the source of the output MOSFET. In a typical circuit, current flows from IN to OUT toward the load. If VOUT is greater than VIN, current will flow from OUT to IN, since the switch is bidirectional when enabled. The output MOSFET and driver circuitry are also designed to allow the MOSFET source to be externally forced to a higher voltage than the drain (VOUT > VIN ) when the switch is disabled. In this situation, the TS2026 prevents undesirable current flow from OUT to IN. Thermal Shutdown Thermal shutdown is employed to protect the device from damage should the die temperature exceed safe margins due mainly to short circuit faults. Each channel employs its own thermal sensor. Thermal shutdown shuts off the output MOSFET and asserts the FLG output if the die temperature reaches 140 oC and the overheated channel is in current limit. The over channel will be shut off. Upon determining a thermal shutdown condition. The TS2026 will automatically reset its output when the die temperature cools down to 120 oC . The TS2026 output and FLG signal will continue to cycle on and off until the device is disabled or the fault is removed. Figure 1. Depicts typical timing. Depending on PCB layout, package, ambient temperature, etc., it may take several hundred milliseconds from the incidence of the fault to the output MOSFET being shut off. This time will be shortest in the case of dead short on the output. Power Dissipation The device’s junction temperature depends on several factors such as the load, PCB layout, ambient temperature and package type. Equations that can be used to calculate power dissipation of each channel and junction temperature are found below. PD = RDS(ON) x IOUT 2 Total power dissipation of the device will be the summation of PD for both channels. To relate this to junction temperature, the following equation can be used: TJ = PD x θJA + TA Where: TJ = junction temperature TA = ambient temperature θJA = is the thermal resistance of the package Current Sensing and Limiting The current-limit threshold is preset internally. The preset level prevents damage to the device and external load but still allows a minimum current of 500mA to be delivered to the load. The current-limit circuit senses a portion of the output MOSFET switch current. The current-sense resistor shown in the block diagram is virtual and has no voltage drop. The reaction to an over current condition varies with three scenarios. Switch Enable into Short-Circuit If a switch is enabled into a heavy load or short-circuit, the switch immediately enters into a constant-current mode, reducing the output voltage. The FLG signal is asserted indicating an over current condition. Switch Enable Applied to Enabled Output When a heavy load or short-circuit is applied to an enabled switch, a large transient current may flow until the current limit circuitry responds. Once this occurs the device limits current to less than the short circuit current limit specification. Current-Limit Response-Ramped Load The TS2026 current-limit profile exhibits a small fold back effect of about 200mA. Once this current-limit threshold is exceeded the device switches into a constant current mode. It is important to note that the device will supply current up to the current-limit threshold Fault Flag The FLG signal is an N-channel open-drain MOSFET output. FLG is asserted (active-low) when either an over current or thermal shutdown condition occurs. In the case of and over current condition, FLG will be asserted only after the flag response delay time, tD, has elapsed. This ensured that FLG is asserted only upon valid over current conditions and that erroneous error reporting is eliminated. For example, false over current condition can occur during hot plug event when a highly capacitive load is connected and causes a high transient inrush current that exceeds the current-limit threshold for up to 1ms. The FLG response delay time tD is typically 3ms. Undervoltage Lockout Undervolrage lockout (UVLO) prevents the output MOSFET from turning on until VIN exceeds approximately 2.5V. Undervoltage detection function only when the switch is enabled. |
Số phần tương tự - TS2026CS |
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Mô tả tương tự - TS2026CS |
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