SC206KSIT
120 kHz Bandwidth, High Voltage Isolation
Current Sensor with Integrated Overcurrent Detection
Setting Overcurrent Fault Switchpoint
The VOC needed for setting the overcurrent fault switchpoint can be calculated as follows:
VOC = 1.17 × Sens × | IOC | ,
where VOC is in mV, Sens in mV/A, and IOC (overcurrent fault switchpoint) in A.
| Ioc | is the overcurrent fault switchpoint for a bidirectional (AC) current, which means a
bi-directional sensor will have two symmetrical overcurrent fault switchpoints, +IOC and –IOC
See the following graph for IOC and VOC ranges:
.
Example:For SC206KSIT, if required overcurrent fault switchpoint is 10 A, and VCC = 5 V, then the
required VOC can be calculated as follows:
VOC = 1.17 × Sens × IOC = 1.17 × 151 × 10 = 1767 (mV)
Overcurrent Fault Operation
The primary concern with high-speed fault detection is that noise may cause false tripping. Various
applications have or need to be able to ignore certain faults that are due to switching noise or other
parasitic phenomena, which are application dependant. The problem with simply trying to filter out
this noise in the main signal path is that in high-speed applications, with asymmetric noise, the act of
filtering introduces an error into the measurement.
To get around this issue, and allow the user to prevent the fault signal from being latched by noise, a
circuit was designed to slew the
pin voltage based on the value of the capacitor from that pin
FAULT
to ground. Once the voltage on the pin falls below 2 V, as established by an internal reference, the
fault output is latched and pulled to ground quickly with an internal N-channel MOSFET.
Fault Walk-through
The following walk-through references various sections and attributes in the figure below. This figure
shows different fault set/reset scenarios and how they relate to the voltages on the
pin,
FAULT
FAULT_EN pin, and the internal Overcurrent (OC) Fault node, which is invisible to the customer.
1. Because the device is enabled (FAULT_EN is high for a minimum period of time, the Fault
Enable Delay, tFED , 15 μs typical) and there is an OC fault condition, the device
pin
FAULT
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SECELECTRONICS [ SEC Electronics Inc. ]
