XRP7714 Datasheet, PDF (15/27 Pages) Exar Corporation – Quad Channel Digital PWM Step Down Controller

XRP7714
Quad Channel Digital PWM Step Down Controller
When an under voltage fault condition occurs (either on VIN1 or VIN2), the fault flag register is set
and all of the XRP7714 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.
OUTPUT VOLTAGE SETTING AND MONITORING
The Output Voltage setting is controlled by the SET_VOUT_TARGET_CHx register. This register
allows the user to set the output voltage with a resolution of 50mV for output voltages between 0
and 2.5V and with a resolution of 100mV for output voltages between 2.6V and 5.1V. Output
voltages higher than 5.1V can be achieved by adding an external voltage divider network. The
output voltage of a particular channel can be read back using the READ_VOUTx register.
Output Voltage from 0.9V to 5.1V
Per the equation below, for values between 0.9V and 5.1V the output voltage is equal to the binary
number stored in the SET_VOUT_TARGET_CHx register multiplied by 50mV. When programming an
© 2010 Exar Corporation
15/27
Rev. 1.1.3