ISL78227 Datasheet, PDF (34/43 Pages) Intersil Corporation – 2-Phase Boost Controller with Integrated Drivers

ISL78227
VIN_OV
FAULT NAME
OC_AVG
OC2_PEAK
VOUT_OV
PLLCOMP_SHORT
PLL_LOCK
TABLE 3. FAULT NAMES LIST FOR THE HICCUP OR LATCH-OFF FAULT RESPONSE
FAULT RESPONSE
HIC/LATCH = VCC: HICCUP
HIC/LATCH = GND: LATCH-OFF
DESCRIPTIONS
Set by the HIC/LATCH pin
Input overvoltage fault (VIN_PIN >58V) protection
response is Hiccup when HIC/LATCH = VCC, and Latch-off
when HIC/LATCH = GND
Set by the HIC/LATCH pin
Input average overcurrent fault (IMON_PIN >2V) protection
response is Hiccup when HIC/LATCH = VCC, and Latch-off
when HIC/LATCH = GND
Set by the HIC/LATCH pin
Peak overcurrent fault (I_SENx >105µA) protection response
is Hiccup when HIC/LATCH = VCC, and Latch-off when
HIC/LATCH = GND
Set by the HIC/LATCH pin
Output overvoltage fault (FB_PIN >120%*VREF_1.6V)
protection response is Hiccup when HIC/LATCH = VCC, and
Latch-off when HIC/LATCH = GND
Set by the HIC/LATCH pin
PLLCOMP_SHORT fault (PLLCOMP_PIN >1.7V) protection
response is Hiccup when HIC/LATCH = VCC, and Latch-off
when HIC/LATCH = GND
Set by the HIC/LATCH pin
PLL loop fault (detect the minimum frequency of 37kHz as
typical) protection response is Hiccup when
HIC/LATCH = VCC, and Latch-off when HIC/LATCH = GND
INPUT OVERVOLTAGE FAULT PROTECTION
As shown in Figure 3 on page 7, the ISL78227 monitors the VIN
pin voltage divided by 48 (VIN/48) as the input voltage
information. This fault detection is active at the beginning of
soft-start (t₅ as shown in Figure 58 on page 29).
The VIN_OV comparator compares VIN/48 to 1.21V reference to
detect if VIN_OV fault is triggered. Equivalently, when V_IN >58V
(for 5µs), VIN_OV fault event is triggered. The PGOOD pin will be
pulled low.
At the same time the VIN_OV fault condition is triggered, the
ISL78227 will respond with fault protection actions to shut down
the PWM switching and enters either Hiccup or Latch-off mode
depending on HIC/LATCH pin configuration as described in
“Selectable Hiccup or Latch-Off Fault Response” on page 33 and
Table 3 on page 34.
Under the selection of Hiccup response for the VIN_OV fault,
when the output voltage falls down to be lower than the VIN_OV
threshold 58V, the device will return to normal switching through
Hiccup soft-start. PGOOD will be released to be pulled high after
a 0.5ms delay.
OUTPUT OVERVOLTAGE FAULT PROTECTION
The ISL78227 monitors the FB pin voltage to detect if output
overvoltage fault (VOUT_OV) occurs. This fault detection is active
at the beginning of soft-start (t₅ as shown in the Figure 58 on
page 29).
If the FB pin voltage is higher than 120% of the voltage
regulation reference VREF_1.6V, the VOUT_OV comparator is
triggered to indicate VOUT_OV fault and the PGOOD pin will be
pulled low.
At the same time, when a VOUT_OV fault is triggered, the
ISL78227 will respond with fault protection actions to shut down
the PWM switching and enters either Hiccup or Latch-off mode
depending on HIC/LATCH pin configuration as described in
“Selectable Hiccup or Latch-Off Fault Response” on page 33 and
Table 3 on page 34.
Under the selection of Hiccup response for the VOUT_OV fault,
when the output voltage falls down to be lower than the VOUT_OV
threshold of 120%*VREF_1.6V minus 4% hysteresis, the device
will return to normal switching through Hiccup soft-start. The
PGOOD pin will be released to be pulled high after 0.5ms delay.
Equivalently the V_OUT overvoltage threshold is set at the same
percentage of V_OUT target voltage V_{OUT_TARGET} (set by
VREF_1.6V) since the device uses the same FB voltage to
regulate the output voltage with the same resistor divider
between V_OUT and the FB pin (refer to Equation 2 on page 25).
Therefore the V_OUT overvoltage protection threshold is set at
120% of V_{OUT_TARGET}. According to Equation 2 on page 25, the
V_OUT overvoltage protection threshold can be calculated using
Equation 18.
VOUT_OVP
=
1.2

1.6

1

+
RR_{-----FF----BB----21-}
(EQ. 18)
OUTPUT UNDERVOLTAGE INDICATION
The ISL78227 monitors the FB pin voltage to detect if output
undervoltage (VOUT_UV) occurs.
If the FB pin voltage is lower than 80% of the voltage regulation
reference VREF_1.6V, the VOUT_UV comparator is triggered to
indicate VOUT_UV occurring and the PGOOD pin will be pulled
low. But there is no fault protection actions for the VOUT_UV
condition, meaning the ISL78227 continue to keep PWM
switching and normal operation when VOUT_UV occurs.
Submit Document Feedback ₃₄
FN8808.2
February 24, 2016