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© 2012 Exar Corporation

15/28

Rev. 1.2.2

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Over Current Protection (OCP) monitors the current of a channel, and will shutdown the

channel if it surpasses its current threshold. The channel will be automatically restarted

after a 200ms delay.

Under Voltage Lockout (UVLO)

There are two locations where the under voltage can be sensed: VIN1 and VIN2. The

SET_UVLO_WARN_VINx register that sets the under voltage warning set point condition at

100mV increments. When the warning threshold is reached, the Host is informed via a GPIO or by

reading the READ_WARN_FLAG register.

The SET_UVLO_TARG_VINx register that controls the under voltage fault set point condition at

100mV increments. This fault condition will be indicated in the READ_FAULT_WARN register.

When an under voltage fault condition occurs (either on VIN1 or VIN2), the fault flag register is set

and all of the XRP7708 outputs are shut down. The measured input voltages can be read back

using the READ_VIN1 or READ_VIN2 register, and both registers have a resolution of 100mV

per LSB. When the UVLO condition clears (voltage rises above the UVLO Warning Threshold), the

chip can be configured to automatically restart.

VIN1

This is a multi-function pin that provides power to both the Standby Linear Regulator and internal

linear regulators to generate VCCA, VDD, and the Standby LDO (LDOUT).

It is also used as a UVLO detection pin. If Vin1 falls below its user programmed limit, all channels

are shut down.

VIN2

VIN2 is required to be tied to VIN1 pin. It can be used as a UVLO detection pin. If VIN2 falls below

its user programmed limit, all channels are shut down.

Temperature Monitoring and Over Temperature Protection (OTP)

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Reading the junction temperature

This register allows the user to read back the temperature of the IC. The temperature is expressed

in Kelvin with a maximum range of 520K, a minimum of 200K, and an LSB of 5 degrees K. The

temperature can be accessed by reading the READ_VTJ register.

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Over Temperature Warning

There are also warning and fault flags that get set in the READ_OVV_UVLO_OVT_FLAG register.

The warning threshold is configurable to 5 or 10 Degrees C below the fault threshold. When the

junction temperature reaches 5 or 10 Degrees C below the user defined set point, the over-

temperature warning bit [OTPW] gets set in the READ_OVV_UVLO_OVT_FLAG register to warn the

user that the IC might go into an over temperature condition (and shutdown all of the regulators).

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Over Temperature Fault

If the over temperature condition occurs both the OTP and OTPW bits will be set in the

operational). The actual over temperature threshold can be set by the user by using a 7bit

SET_THERMAL_SHDN register with an LSB of 5K.

If the over temperature fault condition clears, then the IC can be set to restart the chip

automatically. The restart temperature threshold can be set by the SET_THERMAL_RESTART

register.