The MAX17527A offers adjustable protection boundaries for systems against input voltage faults and overcurrent faults. In addition, the MAX17527A offers a programmable power limiting function. Input-voltage faults (with positive polarity) are protected up to +60V by an internal nFET featuring low ON-resistance (30mΩ typ). The device features fixed or programmable overvoltage lockout (OVLO) and undervoltage lockout (UVLO) thresholds by using internal or external voltage-dividers. Factory preset internal fixed thresholds can be invoked by connecting the OVLO and/or UVLO pin(s) to GND. Input undervoltage protection can be programmed between 5.5V and 59V, while the overvoltage protection can be independently programmed between 6V and 60V.
Input reverse-polarity protection is realized using an external nFET that is controlled by the MAX17527A. The magnitude of reverse-polarity voltage protection is dependent on the operating load-bus voltage (VOUT) and the voltage blocking capability of the external nFET. For example, for protection down to a -55V input range with VOUT = 30V, an external nFET rated at 85V is needed. The external nFET is also needed for the optional reverse-current protection. If reverse polarity protection and reverse-current protection are not needed, SN must be connected to IN and GN must be left unconnected. The MAX17527A is tolerant against accidental output reverse-polarity application due to incorrect wiring across the output terminals.
The current limit of the device is programmed by connecting a resistor from the SETI pin to GND. The current limit can be programmed from 0.6A to 6.0A. When the current through the device reaches or exceedes the set current limit, the resistance of the internal nFET is modulated to limit the current. The device offers three current limit behavioral modes: Continuous, Auto-retry, and Latch-off modes.
The SETI pin presents a current proportional to the device current under normal operation. Together with the current limit program resistor (between SETI and GND), the SETI pin presents a voltage that is proportional to the device current. This voltage can be read by a monitoring system for recording instantaneous current of the device.
The power limit function is realized either at the input supply side or output load side by sampling the input or output voltage through a potential divider connecting to the PLIM pin. The power limit feature reduces the programmed current limit when the external voltage increases above the programmed threshold. The device can be turned On or Off through enable input EN by a master supervisory system. This allows the master supervisory system to Turn On or Off the power delivery to connected loads.
The device offers loss-of-ground protection where it safely turns Off the device operation during a loss-of-ground fault event, i.e., when the safety ground fuse opens up in a redundant-safety application.
The device offers a status announcement signal FLAG) to indicate operational and fault signals. FLAG is an open drain pin, and requires an external pullup resistor to the appropriate system interface voltage. The device also offers internal thermal shutdown protection against excessive power dissipation.
APPLICATIONS
- Loss of Ground Protection
- UL1310 Class 2 Power Limiter
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