Active channel current limitation combined with thermal shutdown, independent for each channel, and automatic restart, protect the device against overload.
Additional embedded functions are: loss of GND protection that automatically turns off the device outputs in case of ground disconnection, undervoltage shutdown with hysteresis, Power Good diagnostic for valid supply voltage range recognition, output enable function for immediate power outputs ON/OFF, and programmable watchdog function for microcontroller safe operation; case overtemperature protection to control the IC case temperature.
The device embeds a four-wire SPI serial peripheral with selectable 8 or 16-bit operations; through a select pin the device can also operate with a parallel interface.
Both the 8-bit and 16-bit SPI operations are compatible with daisy chain connection.
The SPI interface allows command of the output driver by enabling or disabling each channel featuring, in 16-bit format, a parity check control for communication robustness. It also allows the monitoring of the status of the IC signaling Power Good, overtemperature condition for each channel, IC pre-warning temperature detection.
Built-in thermal shutdown protects the chip from overtemperature and short-circuit. In overload condition, the channel turns OFF and ON again automatically after the IC temperature decreases below a threshold fixed by a temperature hysteresis so that junction temperature is controlled. If this condition makes case temperature reaching case temperature limit, TCSD, overloaded channels are turned OFF and restart, non-simultaneously, when case and junction temperature decrease below their own reset threshold. If the case of thermal reset, the channels loaded are not switched on until the junction temperature reset event. Non-overloaded channels continue to operate normally. Case temperature above TCSD is reported through the TWARN open drain pin.
An internal circuit provides a not latched common FAULT indicator reporting if one of the following events occurs: channel OVT (overtemperature), parity check fail. The Power Good diagnostic warns the controller that the supply voltage is below a fixed threshold.
The watchdog function is used to detect the occurrence of a software fault of the host controller. The watchdog circuitry generates an internal reset on expiry of the internal watchdog timer. The watchdog timer reset can be achieved by applying a negative pulse on the WD pin. The watchdog function can be disabled by the WD_EN dedicated pin. This pin also allows the programming of a wide range of watchdog timings.
An internal LED matrix driver circuitry (4 rows, 2 columns) allows the detection of the status of the single outputs. An integrated step-down voltage regulator provides supply voltage to the internal LED matrix driver and logic output buffers and can be used to supply the external optocouplers if the application requires isolation. The regulator is protected against short-circuit or overload conditions by means of pulse-by-pulse current limit with a peak current control loop.