zl2106 Intersil Corporation, zl2106 Datasheet - Page 24

• Manufacturer Part Number: zl2106
• Description: 6a Digital-dc Synchronous Step-down Dc-dc Converter
• Manufacturer: Intersil Corporation

7. Power Management Functional Description
7.1 Input Undervoltage Lockout
The input undervoltage lockout (UVLO) prevents the
ZL2106 from operating when the input falls below a
preset threshold, indicating the input supply is out of
its specified range. The UVLO threshold (V
be set to either 4.5 V or 10.8 V using the SS pin
according to Table 10.
The UVLO voltage can also be set to any value
between 2.85 V and 16 V via the I
Once an input undervoltage fault condition occurs, the
device can respond in a number of ways as follows:
1. Continue operating without interruption.
2. Continue operating for a given delay period,
3. Initiate an immediate shutdown until the fault has
The default response from a UVLO fault is an
immediate shutdown of the device. Please refer to
Application Note AN33 for details on how to configure
the UVLO threshold or to select specific UVLO fault
response options via the I
7.2 Output Overvoltage Protection
The ZL2106 offers an internal output overvoltage
protection circuit that can be used to protect sensitive
load circuitry from being subjected to a voltage higher
than its prescribed limits. A hardware comparator is
used to compare the actual output voltage (seen at the
VSEN pin) to a threshold set to 15% higher than the
target output voltage (the default setting). If the VSEN
voltage exceeds this threshold, the PG pin will de-
assert and the device can then respond in a number of
ways as follows:
1. Initiate an immediate shutdown until the fault has
2. Turn off the high-side MOSFET and turn on the
followed by shutdown if the fault still exists. The
device will remain in shutdown until instructed to
restart.
been cleared. The user can select a specific number
of retry attempts.
been cleared. The user can select a specific number
of retry attempts.
low-side MOSFET. The low-side MOSFET
remains on until the device attempts a restart.
24
2
C/SMBus interface.
2
C/SMBus interface.
UVLO
) can
ZL2106
The default response from an overvoltage fault is to
immediately shut down. For continuous overvoltage
protection when operating from an external clock, the
only allowed response is an immediate shutdown.
Please refer to Application Note AN33 for details on
how to select specific overvoltage fault response
options via I
7.3 Output Pre-Bias Protection
An output pre-bias condition exists when an externally
applied voltage is present on a power supply’s output
before the power supply’s control IC is enabled.
Certain applications require that the converter not be
allowed to sink current during start up if a pre-bias
condition exists at the output. The ZL2106 provides
pre-bias protection by sampling the output voltage
prior to initiating an output ramp.
If a pre-bias voltage lower than the target voltage exists
after the pre-configured delay period has expired, the
target voltage is set to match the existing pre-bias
voltage and both drivers are enabled. The output
voltage is then ramped to the final regulation value at
the ramp rate set by the SS pin.
The actual time the output will take to ramp from the
pre-bias voltage to the target voltage will vary
depending on the pre-bias voltage but the total time
elapsed from when the delay period expires and when
the output reaches its target value will match the pre-
configured ramp time (see Figure 17).
2
C/SMBus.
Data Sheet Revision 2/19/2009
www.intersil.com