32
FN6849.3
December 16, 2011
Please refer to Application Note AN2015 for details
on how to select specific overcurrent fault response
options via the I
2
C/SMBus interface.
6.5 Thermal Protection
The ZL2005P includes an on-chip thermal sensor that
continuously measures the internal temperature of the
die and will shut down the device when the tempera
-
ture exceeds the preset limit. The default temperature
limit is set to 125°C in the factory, but the user may set
the limit to a different value if desired. See Applica
-
tion Note AN2013 for details. Note that setting a
higher thermal limit via the I
2
C/SMBus interface may
result in permanent damage to the device. Once the
device has been disabled due to an internal tempera
-
ture fault, the user may select one of several fault
response options as follows:
1. Initiate a shutdown and attempt to restart an infi-
nite number of times with a preset delay time.
2. Initiate a shutdown and attempt to restart the
power supply a preset number of times with a pre
-
set delay between attempts.
3. Continue operating throughout a specific delay
time, followed by shutdown.
4. Continue operating throughout the fault (this
could result in permanent damage to the power
supply).
5. Initiate an immediate shutdown.
If the user has configured the device to restart, the
device will wait the preset delay period (if configured
to do so) and will then check the temperature. If the
temperature has dropped below a value that is approx
-
imately 15°C lower than the selected temperature limit
(the over-temperature warning threshold), the device
will attempt to re-start. If the temperature is still
above the over-temperature warning threshold, the
device will wait the preset delay period and retry
again.
The default response from a temperature fault is an
immediate shutdown of the device. The device will
continuously check for the presence of the fault condi
-
tion. If the fault condition is no longer present, the
ZL2005P will be re-enabled.
Please refer to Application Note AN2013 for details
on how to select specific temperature fault response
options via the I
2
C/SMBus interface.
6.6 Voltage Tracking
Numerous high performance systems place stringent
demands on the order in which the power supply volt
-
ages are turned on. This is particularly true when
powering FPGAs, ASICs, and other advanced proces
-
sor devices that require multiple supply voltages to
power a single die. In most cases, the I/O operates at a
higher voltage than the Core and therefore the Core
supply voltage, must not exceed the I/O supply voltage
by some amount (typically 300 mV).
Voltage tracking protects these sensitive ICs by limit-
ing the differential voltage between multiple power
supplies during the power-up and power down
sequence. The ZL2005P integrates a lossless tracking
scheme that allows its output to track a voltage that is
applied to the VTRK pin with no external components
required. The VTRK pin is an analog input that, when
tracking mode is enabled, configures the voltage
applied to the VTRK pin to act as a reference for the
device’s output regulation.
The ZL2005P offers two modes of tracking:
1. Coincident. This mode configures the ZL2005P to
ramp its output voltage at the same rate as the volt
-
age applied to the VTRK pin.
2. Ratiometric. This mode configures the ZL2005P
to ramp its output voltage at a rate that is a per
-
centage of the voltage applied to the VTRK pin.
The default setting is 50%, but an external resistor
string may be used to configure a different track
-
ing ratio.
Figure 21 illustrates the typical connection and the two
tracking modes.
The Tracking feature is not supported for ZL2005P
devices in a current sharing group.
ZL2005P
