XR77129 Datasheet, PDF (25/28 Pages) Exar Corporation – 40V Quad Output Digital PWM/PFM

Downloading Configuration to XR77129
A key benefit of Exar’s programmable power technology is
the ability to easily update the design and chip configura-
tion during development. The best way to do this is to pro-
gram the RAM memory rather than programming the
FLASH NVM.
XR77129
PA 5.2 provides a RAM download function accessible
through the Dashboard or through the “Tools” menu.
RAM programming requires that there is no valid configura-
tion in the FLASH NVM. A valid configuration is loaded in
the chip if in the Dashboard window, the “Reset Chip” (F8)
button is clicked and after a short delay the “Chip Ready”
indicates “Yes”. When a new configuration is loaded into
RAM with a chip that already contains a valid configuration
in FLASH NVM, the first step will be to invalidate the FLASH
configuration. The device will be reset to clear the prior
RAM content and then the new run time configuration gets
loaded. PA 5.2 will indicate that it successfully downloaded
the configuration to run time registers after which the “Chip
Ready” indicator will be asserted by PA 5.2 acting as a
host.
By clicking on the Flash button, user will start programming
sequence of the design configuration into the Flash NVM.
After the programming sequence completes, the chip will
reset (if the Automatically Reset After Flashing box is
checked), and boot the design configuration from the Flash.
For users that wish to create their own programming proce-
dure so they can re-program Flash in-circuit using their sys-
tem software, they should contact Exar for a list of I²C Flash
Commands needed or refer to ANP-38.
If the configuration changes I²C address, the device will
respond to the new address at this point.
For users that wish to create their own downloading proce-
dure, they can refer to ANP-39.
Programming XR77129
Once the design has been tested and verified its configura-
tion can permanently be saved into FLASH NVM.
XR77129 is a FLASH based device which means its config-
uration can be programmed into FLASH NVM and re-pro-
grammed a number of times.
Programming of FLASH NVM is done through PA 5.2.
Enabling XR77129
XR77129 has an internal pull-up ensuring it gets enabled
as soon as internal voltage supplies have ramped up and
are in regulation.
Driving the Enable pin low externally will keep the controller
in the shut-down mode. A simple open drain pull down is
the recommended way to shut XR77129 down.
If the Enable pin is driven high externally to control
XR77129 coming out of the shut-down mode, care must be
taken in such a scenario to ensure the Enable pin is driven
high after VCC gets supplied to the controller.
A diode in series with a resistor between the LDO5 and
ENABLE pins may offer a way to more quickly pull down the
LDO5 output when the ENABLE pin is pulled low.
© 2014 Exar Corporation
25 / 28
exar.com/XR77129
Rev 1A