Cirrus Logic CS1501 - Manual (Page 13)

CS1501
DS927F4 13
5.12 Open/Short Loop Protection
If the PFC output sense resistor, R
IFB
, fails (open or short to
GND), the measured output voltage decreases at a slew rate of
about 2 V/
s, which is determined by the ADC sampling rate.
The IC stops the gate drive when the measured output voltage is
lower than the measured line voltage. The IC resumes gate drive
switching when the current into the IFB pin becomes larger than
or equal to the current into the IAC pin and V
link
is greater than
the peak of the line voltage (V
rect(pk)
). The maximum response
time of open/short loop protection for R
IFB
is about 150 s.
If the PFC input sense resistor R
IAC
fails (open or short to GND),
the current reference signal supplied to the IC on pin IAC falls
to zero.
5.13 Internal Overtemperature Protection
An internal thermal sensor triggers a shutdown when the
temperature exceeds 135°C (nominal) on the silicon. The
sensor sends a signal to the core that supplies current to all
internal digital logic, cutting off power from them. Once the
temperature of the IC has dropped by 9°C (nominal), the
sensor resets, allowing power to the logic.
5.14 Standby (STBY) Function
The standby (STBY) pin provides a means by which an
external signal can cause the CS1501 to enter a
non-operating, low-power state. The STBY input is intended to
be driven by an open-collector/open-drain device. Internal to
the pin, there is a pull-up resistor connected to the V
DD
pin, as
shown in Figure 21. Since the pull-up resistor has a high
impedance, a filter capacitor (up to 1000pF) may be required
on this pin.
Figure 21. STBY Pin Connection
When the STBY pin is not used, it is recommended that the pin
be tied to V
DD
(pulled high).
<1 nF
600k
See Text
VDD
STBY
GND
CS1501
8
6
2