XRP7714 Datasheet, PDF (13/27 Pages) Exar Corporation – Quad Channel Digital PWM Step Down Controller

XRP7714
Quad Channel Digital PWM Step Down Controller
Phase 1
VIN1
ENABLE_PIN
VCC
VDD
VDDOK
SYS_RESET
CONFIG_TRANSFER
CHIP_READY
Phase 2
Phase 3
Fig. 21: Power Up Sequence
INTERNAL LDO POWER-UP PHASE – PHASE 1
When the ENABLE pin is set, internal VCC and VDD power up upon the power up of VIN1. Once the
bandgap reference is stable and VCC and VDD fall into the acceptable range, an internal VDDOK
flag is generated. A SYS_RESET remains low for a few clock cycles to reset all the internal
registers. After that the internal CONFIGURATION_TRANSFER signal raises high and the chip
transits to the second phase.
CONFIGURATION TRANSFER PHASE – PHASE 2
In this phase, the contents in the configuration memory are transferred to the internal registers.
The internal oscillator switches to the programed switching frequency. The GPIO pins are properly
configured as either inputs or outputs. If the chip is programmed to run in the I²C mode, GPIO4
and GPIO5 are configured to serve as SDA and SCL for the I²C bus. If chip is programmed to run in
the NON-I²C mode, then these two pins can be used as GPIO4 and GPIO5 respectively.
CHIP READY PHASE – PHASE 3
In this phase, the chip is ready for normal operation. An internal CHIP_READY flag goes high and
enables the I²C to acknowledge the Host’s serial commands. Channels that are configured as
always-on channels are enabled. Channels that are configured to be enabled by GPIOs are also
enabled if the respective GPIO is asserted.
STANDBY LOW DROP-OUT REGULATOR
This 100mA low drop-out regulator can be programmed as 3.3V or 5V in SET_STBLDO_EN_CONFIG
register. Its output is seen on the LDOOUT Pin. This LDO is fully controllable via the Enable Pin
(configured to turn on as soon as power is applied), a GPIO, and/or I²C communication.
The 5V output setting of the regulator is only available if VIN1 is above 6.5V, and the 3.3V output
setting is available for the entire VIN1 range from 4.75 to 25V.
ENABLING, DISABLING AND RESET
The XRP7714 is enabled via raising the ENABLE Pin high. The chip can then be disabled by
lowering the same ENABLE Pin. There is also the capability for resetting the Chip via an I²C
SOFTRESET Command.
© 2010 Exar Corporation
13/27
Rev. 1.1.3