SC206KSIT
120 kHz Bandwidth, High Voltage Isolation
Current Sensor with Integrated Overcurrent Detection
starts discharging.
2. When the
pin voltage reaches approximately 2 V, the fault is latched, and an internal
FAULT
NMOS device pulls the
pin voltage to approximately 0 V. The rate at which the
FAULT
pin slews downward (see [4] in the figure) is dependent on the external capacitor, C ,
FAULT
on the
OC
pin.
FAULT
3. When the FAULT_EN pin is brought low, the
pin starts resetting if no OC fault
FAULT
condition exists, and if FAULT_EN is low for a time period greater than tOCH. The internal
NMOS pull-down turns off and an internal PMOS pullup turns on (see [7] if the OC fault
condition still exists).
4. The slope, and thus the delay to latch the fault is controlled by the capacitor, COC, placed on the
pin to ground. During this portion of the fault (when the
pin is between VCC and
FAULT
FAULT
2 V), there is a 3 mA constant current sink, which discharges COC. The length of the fault delay, t
is equal to:
COC ×(VCC − 2V )
t =
3mA
where VCC is the device power supply voltage in volts, t is in seconds and COC is in Farads. This
formula is valid for RPU equal to or greater than 330 kΩ. For lower-value resistors, the current
flowing through the RPU resistor during a fault event, IPU , will be larger. Therefore, the current
discharging the capacitor would be 3 mA – IPU and equation 1 may not be valid.
5. The
pin did not reach the 2 V latch point before the OC fault condition cleared. Because
FAULT
of this, the fixed 3 mA current sink turns off, and the internal PMOS pull-up turns on to recharge
COC through the pin.
FAULT
6. This curve shows VCC charging external capacitor COC through the internal PMOS pull-up. The
slope is determined by COC.
7. When the FAULT_EN pin is brought low, if the fault condition still exists, the latched
FAULT
pin will be pulled low by the internal 3mA current source. When fault condition is removed then
the Fault pin charges as shown in step 6.
8. At this point there is a fault condition, and the part is enabled before the
pin can charge to
FAULT
VCC. This shortens the user-set delay, so the fault is latched earlier. The new delay time can be
calculated by equation 1, after substituting the voltage seen on the
pin for V .
FAULT
CC
1
1
1
Vcc
4
6
4
4
8
5
6
4
2
2
2
6
2V
0V
7
3
Fault_En
Input
OC Fault Condition
(Active High)
12/13
SECELECTRONICS [ SEC Electronics Inc. ]
