XRP7704 Datasheet, PDF (27/31 Pages) Exar Corporation – Quad-Output Digital PWM Buck Controller

REV 1.1.0
XRP7704
Quad-Output Digital PWM Buck Controller
Fault and Warning Indication
The GPIOs can be configured to signal Fault or Warning conditions when they occur in the chip. Each GPIO can
be configured to signal one of the following:
• OCP Fault on Channel 1 - 4
• OCP Warning on Channel 1 - 4
• OVP Fault on Channel 1 - 4
• UVLO Fault on VIN1 or VIN2
• UVLO Warning on VIN1 or VIN2
• Over Temperature Fault or Warning
I²C Communication
The I²C communication is standard 2-wire communication available between the Host and the IC. This interface
allows for the full control, monitoring, and reconfiguration of the semiconductor.
The I²C Slave address is saved in the NVM. Therefore, each customer can choose the 7-bit Slave Address which
will work best in their design (in relation to any other I²C devices on the bus).
External Component Selection
Inductor Selection
Select the Inductor for inductance L and saturation current Isat. Select an inductor with Isat higher than the
programmed over current limit. Calculate inductance from:
Where:
VIN is the converter input voltage
VOUT is the converter output voltage
fs is the switching frequency
Irip is the inductor peak-to-peak current ripple (nominally set to 30% of Iout)
Keep in mind that a higher Irip results in a smaller inductance value which has the advantages of smaller size,
lower DC equivalent resistance (DCR), and allows the use of a lower output capacitance to meet a given step
load transient. A higher Irip, however, increases the output voltage ripple, requires higher saturation current limit,
and increases critical conduction. Notice that this critical conduction current is half of Irip.
Capacitor Selection
Output Capacitor Selection
Select the output capacitor for voltage rating, capacitance and Equivalent Series Resistance (ESR). Nominally the
voltage rating is selected to be at least twice as large as the output voltage. Select the capacitance to satisfy the
specification for output voltage overshoot/undershoot caused by the current step load. A sudden decrease in the
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