XRP7708EVB Exar Corporation, XRP7708EVB Datasheet - Page 15

• Manufacturer Part Number: XRP7708EVB
• Description: EVAL BOARD FOR XRP7708
• Manufacturer: Exar Corporation
• Type: PMIC Solutionsr

Specifications of XRP7708EVB

• Main Purpose: DC/DC, Step Down
• Outputs And Type: *
• Voltage - Output: *
• Current - Output: *
• Voltage - Input: *
• Regulator Topology: Buck
• Frequency - Switching: *
• Board Type: Fully Populated
• Utilized Ic / Part: XRP7708
• Board Size: 6 mm x 6 mm x 0.8 mm
• Interface Type: I2C
• Maximum Operating Temperature: + 125 C
• Operating Supply Voltage: 6.5 V to 20 V
• Product: Power Management Development Tools
• Sense Voltage (max): 5 mV
• Dimensions: 6 mm x 6 mm x 0.8 mm
• Silicon Manufacturer: Exar
• Silicon Core Number: XRP7708
• Kit Application Type: Power Management - Voltage Regulator
• Application Sub Type: Step Down DC/DC Controller
• For Use With/related Products: XRP7708
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 1016-1346

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.
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).
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 I
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.
O
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.
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
output voltage from 2.6V to 5.1V, odd binary values should be avoided. As a result, the set
resolution for an output voltage higher than 2.5V is 100mV.
To set the output voltage higher than 5.1V, the user needs to add an external voltage divider. The
resistors used in the voltage divider should be below 10kΩ. The SET_VOUT_TARGET_CHx register
should be set to 0x32 which is equivalent to an output voltage of 2.5V without the external divider
network. The output voltage regulation in this case might exceed 2% due to extra error from the
resistor divider. R1 and R2 follows the definition below.
© 2010 Exar Corporation
Output Voltage from 0.9V to 5.1V
Output VOUT Higher Than 5.1V
UTPUT
•
•
Over Temperature Warning
Over Temperature Fault
V
OLTAGE
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ETTING AND
Fig. 18: External divider network for high output voltage
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