XRP7714 Datasheet, PDF (16/27 Pages) Exar Corporation – Quad Channel Digital PWM Step Down Controller

XRP7714
Quad Channel Digital PWM Step Down Controller
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.
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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 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.
Vout>5.1V
R1
Voutx pin
R2
Fig. 22: External divider network for high output voltage
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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 ±20mV output voltage accuracy is not guaranteed.
OVER-VOLTAGE PROTECTION (OVP)
The Over-Voltage Protection (OVP) SET_OVVP_REGISTER sets the over-voltage condition in
predefined steps per channel. The over-voltage protection is always active even during soft-start
condition. When the over-voltage condition is tripped, the controller will shut down the channel.
When the channel is shut down the controller will then set corresponding OVP Fault bits in the
READ_OVV_UVLO_OVT_FLAG register.
The VOUT OVP Threshold is 150mV to 300mV above nominal VOUT for a Voltage Target of 2.5V or
less. For the Voltage Target of 2.6V to 5.1V, the VOUT OVP Threshold is 300mV to 600mV.
Once the over-voltage Channel is disabled, the controller will check the
SET_FAULT_RESP_CONFIG_LB and SET_FAULT_RESP_CONFIG_HB to determine whether there are
any “following” channels that need to be shut down. Any following channel will be disabled when
the channel with the Over Voltage Fault is disabled. The channel(s) will remain disabled, until the
Host takes action to enable the channel(s).
Any of the fault and warning conditions can also be configured to be represented using the general
purpose input output pins (GPIO) to use as an interface with non I²C compatible devices. For
further information on this topic see the “GPIO Pins” Section.
During OVP fault shutdown of the channel, the customer has the option to choose two types of
shutdown for each channel. The first shutdown is ‘passive shutdown’ where the IC merely stops
outputting pulses. The second shutdown is a ‘brute force’ shutdown where the GL remains on as
the channel reaches its discharged voltage. Note that if the ‘brute force’ method is chosen, then GL
will permanently remain high until the channel is re-enabled.
© 2010 Exar Corporation
16/27
Rev. 1.1.3