LTC3675 Datasheet, PDF (24/36 Pages) Linear Technology – 7-Channel Confi gurable High Power PMIC

LTC3675
OPERATION
RSTB MASK REGISTER
REGULATOR
V_OUT
92.5% OF PROGRAMMED V_OUT
PGOOD
COMPARATOR
+
–
OTHER UNMASKED
PGOOD OUTPUTS
AND1
UNMASKED
PGOOD OUTPUTS
UNMASKED
AND2
ERROR
OTHER UNMASKED
ERRORS
IRQB MASK REGISTER
V_IN
EXTERNAL PULL-UP RESISTOR
RSTB
CLRINT
V_IN
EXTERNAL PULL-UP RESISTOR
IRQB
SET
CLR
LATCHED STATUS REGISTER
REAL TIME STATUS REGISTER
3675 F04
Figure 4. Simplified Schematic Showing RSTB and IRQB Signal Path
data from the selected register. A STOP command is not
required for the bus read operation.
Immediately after writing data to a register, the contents of
that register may be read back if the bus master issues a
START condition followed by the LTC3675 read address.
ERROR CONDITION REPORTING VIA
RSTB AND IRQB PINS
Error conditions are reported back via the IRQB and RSTB
pins. After an error condition is detected, status data can
be read back to a microprocessor via I²C to determine the
exact nature of the error condition.
Figure 4 is a simplified schematic showing the signal path
for reporting errors via the RSTB and IRQB pins.
All the switching regulators and the LED driver have an
internal power good (PGOOD) signal. When the regulated
output voltage of an enabled switcher rises above 93.5%
of its programmed value, the PGOOD signal will transition
high. When the regulated output voltage falls below 92.5%
of its programmed value, the PGOOD signal is pulled low.
24
If that PGOOD is not masked and stays low for greater than
50μs, then it pulls the RSTB and IRQB pins low, indicating
to a microprocessor that an error condition has occurred.
The 50μs filter time prevents the pins from being pulled
low due to a transient.
The LED driver has a PGOOD signal (PGOOD[7]) that
is used to indicate output voltage status only when it is
configured as a high voltage boost regulator. In all other
operating modes, PGOOD[7] is disabled.
An error condition that pulls the RSTB pin low is not
latched. When the error condition goes away, the RSTB
pin is released and is pulled high if no other error condi-
tion exists.
In addition to the PGOOD signals of the regulators, the
IRQB pin also indicates the status of the overtemperature
and undervoltage flags. The undervoltage and overtem-
perature faults cannot be masked. A fault that causes
the IRQB pin to be pulled low is latched. When the fault
condition is cleared, the IRQB pin is still maintained in its
low state. The user needs to clear the interrupt by using
a CLRINT command.
3675f