ZHCSCO8E June 2014 – May 2019 TPS65283 , TPS65283-1
PRODUCTION DATA.
The TPS65283, TPS65283-1 responds to overcurrent conditions on power switches by limiting the output currents to IOCP_SW level, which is set by external resistor. When the load current is less than the current-limit threshold, the devices are not limiting current. During normal operation, the N-channel MOSFET is fully enhanced, and VSW_OUT = VSW_IN – (ISW_OUT × Rdson_SW). The voltage drop across the MOSFET is relatively small compared to VSW_IN, and VSW_OUT ≈ VSW_IN. When an overcurrent condition is detected, the device maintains a constant output current and reduces the output voltage accordingly. During current-limit operation, the N-channel MOSFET is no longer fully enhanced and the resistance of the device increases. This allows the device to effectively regulate the current to the current-limit threshold. The effect of increasing the resistance of the MOSFET is that the voltage drop across the device is no longer negligible (VSW_IN ≠ VSW_OUT), and VSW_OUT decreases. The amount that VSW_OUT decreases is proportional to the magnitude of the overload condition. The expected VSW_OUT can be calculated by IOCP_SW × RLOAD, where IOCP_SW is the current-limit threshold and RLOAD is the magnitude of the overload condition.
Table 1 shows three possible overload conditions that can occur.
| CONDITIONS | BEHAVIORS |
|---|---|
| Short circuit or partial short circuit present when the device is powered up or enabled | The output voltage is held near zero potential with respect to ground and the TPS65283, TPS65283-1 ramps output current to IOCP_SW. The device limits the current to IOS until the overload condition is removed or the internal deglitch time (8 ms typical) is reached and the device is turned off. The device auto recovers when the overcurrent status is removed. |
| Gradually increasing load (<100 A/s) from normal operating current to IOCP_SW | The current rises until current limit. After the threshold has been reached, the device switches into its current limiting at IOCP_SW. The device limits the current to IOS until the overload condition is removed or the internal deglitch time (8 ms typical) is reached and the device is turned off. The device auto recovers when the overcurrent status is removed. |
| Short circuit, partial short circuit or fast transient overload occurs while the device is enabled and powered on | The device responds to the overcurrent condition within time TIOS (see Figure 3).The current sensing amplifier is overdriven during this time, and needs time for loop response. After TIOS has passed, the current sensing amplifier recovers and limits the current to IOCP_SW. The device limits the current to IOS until the overload condition is removed or the internal deglitch time (8 ms typical) is reached and the device is turned off. The device auto recovers when the overcurrent status is removed. |