ZL2103ALAF datasheet(22/28 Pages) RENESAS

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ZL2103

FN6966 Rev 5.00

Page 22 of 28

May 3, 2011

Output Overcurrent Protection

The ZL2103 can protect the power supply from damage if the

output is shorted to ground or if an overload condition is imposed

on the output. Once the current limit threshold has been selected

(see “Current Sensing and Current Limit Threshold Selection” on

page 19), the user may determine the desired course of action in

response to the fault condition. The following overcurrent

protection response options are available:

1. Initiate a shutdown and attempt to restart an infinite number

of times with a preset delay period between attempts.

2. Initiate a shutdown and attempt to restart a preset number of

times with a preset delay period between attempts.

3. Continue operating for a given delay period, followed by

shutdown if the fault still exists.

4. Continue operating through the fault (this could result in

permanent damage to the power supply).

5. Initiate an immediate shutdown.

6. The default response from an overcurrent fault is an

immediate shutdown of the device. Please refer to

Application Note AN2033 for details on how to select specific

overcurrent fault response options via I2C/SMBus.

Thermal Overload Protection

The ZL2103 includes an on-chip thermal sensor that

continuously measures the internal temperature of the die and

will shutdown the device when the temperature exceeds the

preset limit. The factory default temperature limit is set to

+125°C, but the user may set the limit to a different value if

desired. See Application Note AN2033 for details. Note that

setting a higher thermal limit via the I2C/SMBus interface may

result in permanent damage to the device. Once the device has

been disabled due to an internal temperature fault, the user may

select one of several fault response options as follows:

1. Initiate a shutdown and attempt to restart an infinite number

of times with a preset delay period between attempts.

2. Initiate a shutdown and attempt to restart a preset number of

times with a preset delay period between attempts.

3. Continue operating for a given delay period, followed by

shutdown if the fault still exists.

4. Continue operating through 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 device temperature. If the temperature has dropped

below a threshold that is approximately +15°C lower than the

selected temperature fault limit, the device will attempt to re-

start. If the temperature still exceeds the fault limit 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. Please refer to Application Note AN2033

for details on how to select specific temperature fault response

options via I2C/SMBus.

Voltage Tracking

Numerous high performance systems place stringent demands

on the order in which the power supply voltages are turned on.

This is particularly true when powering FPGAs, ASICs, and other

advanced processor devices that require multiple supply voltages

to power a single die. In most cases, the I/O interface operates at

a higher voltage than the core and therefore the core supply

voltage must not exceed the I/O supply voltage according to the

manufacturers' specifications.

Voltage tracking protects these sensitive ICs by limiting the

differential voltage between multiple power supplies during the

power-up and power down sequence. The ZL2103 integrates a

lossless tracking scheme that allows its output to track a voltage

that is applied to the VTRK pin with no additional 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 ZL2103 offers two modes of tracking. Figure 18 illustrates

the output voltage waveform for the two tracking modes.

1. Coincident. This mode configures the ZL2103 to ramp its

output voltage at the same rate as the voltage applied to the

VTRK pin.

2. Ratiometric. This mode configures the ZL2103 to ramp its

output voltage at a rate that is a percentage of the voltage

applied to the VTRK pin. The default setting is 50%, but an

external resistor may be used to configure a different tracking

ratio.

The master device in a tracking group is defined as the device

that has the highest target output voltage within the group. This

master device will control the ramp rate of all tracking devices

and is not configured for tracking mode. A delay of at least 10ms

must be configured into the master device using the SS pin, and

VOUT

Time

Coincident

Ratiometric

VTRK

VIN

VOUT

VTRK

VOUT

Time

VTRK

FIGURE 18. TRACKING MODES

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