XRP7714_1009 Datasheet, PDF(16/29 Page) Exar Corporation – Quad Channel Digital PWM Step Down Controller

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XRP7714

Quad Channel Digital PWM Step Down Controller

â¢ 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

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

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.

í µí±í µí±í µí±í µí± = í µí±í µí°¸í µí±_í µí±í µí±í µí±í µí±_í µí±í µí°´í µí±í µí°ºí µí°¸í µí±_í µí°¶í µí°»í µí± Ã 50í µí±í µí±

Output VOUT Higher Than 5.1V

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 10kâ¦. 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.

Vout>5.1V

Voutx pin

Fig. 23: External divider network for high output voltage

í µí±í µí±í µí±í µí± = ï¿½í µí µí±í±12 + 1ï¿½ Ã í µí±í µí°¸í µí±_í µí±í µí±í µí±í µí±_í µí±í µí°´í µí±í µí°ºí µí°¸í µí±_í µí°¶í µí°»í µí± Ã 50í µí±í µí±

Output Voltage Lower Than 0.9V

The XRP7714 can be programmed to regulate an output voltage lower than 0.9V. However, in this

case the specification of Â±20mV output voltage accuracy is not guaranteed.

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