XRP7704 Datasheet, PDF (17/31 Pages) Exar Corporation – Quad-Output Digital PWM Buck Controller

REV 1.1.0
XRP7704
Quad-Output Digital PWM Buck Controller
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
XRP7704 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)
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.
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).
Over Temperature Fault
If the over temperature condition occurs both the OTP and OTPW bits will be set in the
READ_OVV_UVLO_OVT_FLAG register and the IC will shut down all channels (but I²C will remain 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.
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