XRP7704 Exar Corporation, XRP7704 Datasheet - Page 14

• 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
XRP7704 FUNCTIONAL DESCRIPTION AND OPERATION
The XRP7704 is a quad-output digital pulse width modulation (DPWM) controller with integrated gate drivers for
the use in synchronous buck switching regulators. Each output voltage can be programmed from 0.9V to 5.1V
without the need of an external voltage divider. The wide range of the programmable DPWM switching frequency
(from 300 KHz to 1.5 MHz) enables the user to optimize for efficiency or component sizes. The digital regulation
loop requires no external passive components for network compensation. The loop performance does not need
to be compromised due to component tolerance, aging, and operating condition. Each digital controller provides a
number of safety features, such as over-current protection (OCP) and over-voltage protection (OVP). The chip
also provides over-temperature protection (OTP) and under-voltage lock-out (UVLO) for two input voltage rails.
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The XRP7704 also has up to 6 GPIOs and a Standby Linear Regulator to provide standby power. An I
C bus
interface is provided to program the IC as well as to communicate with the host for fault reporting and handling,
power rail monitoring, channel enable and disable, Standby Low Drop-out Regulator voltage reconfiguration, and
Standby LDO enable and disable.
The XRP7704 offers a complete solution for soft-start and soft-stop. The delay and ramp of each PWM regulator
can be independently controlled. When a pre-bias voltage is present, the device holds both high-side and low-side
MOSFETs off until the reference voltage ramps up higher than the output voltage. As a result, large negative
inductor current and output voltage disturbance are avoided. During soft-stop, the output voltage ramps down
with a programmable slope until it reaches a pre-set stop voltage. This pre-set value can be programmed
between within zero volts and the target voltage with the same set target voltage resolution (see shutdown
waveforms in Applications).
Register Types
There are two types of registers in the XRP7704: read/write registers and read-only registers. The read/write
registers are used for the control functions of the IC and can be programmed using configuration non-volatile
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memory (NVM) or through an I
C command. The read-only registers are for feedback functions such as
error/warning flags and for reading the output voltage or current.
Non-Volatile Configuration Memory
The non-volatile memory (NVM) in XRP7704 stores the configuration data for the chip and all of the power rails.
This memory is normally configured during manufacturing time. Once a specific bit of the NVM is programmed,
that bit can never be reprogrammed again [i.e. one-time programmable]. During chip power up, the contents in
the NVM are automatically transferred to the internal registers of the chip. Programmed cells have been verified to
be permanent for at least 10 years and are highly reliable.
EXAR CONFIDENTIAL. PROPRIETARY. DO NOT DISTRIBUTE OR COPY.
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