XRP7704 Exar Corporation, XRP7704 Datasheet - Page 20

• Manufacturer Part Number: XRP7704
• Description: Quad-output Digital Pwm Buck Controller
• Manufacturer: Exar Corporation

XRP7704
Quad-Output Digital PWM Buck Controller
REV 1.1.0
Over-Current Fault Handling
When an over-current condition occurs, PWM drivers in the corresponding channels are disabled. After a 200ms
timeout, the controller is re-powered and soft-start is initiated. When the over-current condition is reached 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 similarly restarted. The controller will also set the fault
flags in READ_OVC_FAULT_WARN register.
Typically the over-current fault threshold would be set to 130-140% of the maximum desirable output current. This
will help avoid any over-current conditions caused by transients that would shut down the output channel.
Chip Operation and Configuration
Soft-Start
The SET_SS_RISE_CHx register is a 16 bit register which specifies the soft-start delay and the ramp
characteristics for a specific channel. This register allows the customer to program the channel with a 250us step
resolution and up to a maximum 16ms delay.
Bits [15:10] specify the delay after enabling a channel but before outputting pulses; where each bit represents
250us steps. Bits [9:0] specify the rise time of the channel; these 10 bits define the number of microseconds for
each 50mV increment to reach the target voltage.
Channel Power Up Sequence
EXAR CONFIDENTIAL. PROPRIETARY. DO NOT DISTRIBUTE OR COPY.
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