XR77128 Datasheet, PDF (19/28 Pages) Exar Corporation – Quad Output Digital PWM/PFM

Configuring GPIO/PSIOs
The following functions can be controlled from or forwarded
to any GPIO/PSIO:
XR77128
“PGood Max” is the upper window and “PGood Min” is the
lower window. The minimum and maximum for each of
these values can be calculated with the following equation:
• General Output – set with an I²C command
• General Input – triggers an interrupt; state read with an
I²C command
• Power Group Enable – controls enabling and disabling
of channels placed in Group 1and Group 2
• Power Channel Enable – controls enabling and dis-
abling of a individual channel including LDOOUT
• I²C Address Bit – controls an I²C address bit
• Power OK – indicates that selected channels have
reached their target levels and have not faulted. Multiple
channel selection is available in which case the resulting
signal is the AND logic function of all channels selected
• ResetOut – is delayed Power OK. Delay is programma-
ble in 5ms increments with the range of 0 to 255ms.
When no channels selected, the transition will indicate
the controller has finished the booting process and is
ready to communicate.
• Low VCC – indicates when VCC has fallen below the
UVLO fault threshold and when the UVLO condition
clears (VCC voltage rises above the UVLO warning
level)
• Interrupt – the controller generated interrupt selection
and clearing is done through I²C commands
• HW Power Good – the Power Good hardware monitor-
ing function. It is an output voltage monitoring function
that is a hardware comparison of channel output voltage
against its user defined Power Good threshold limits
(Power Good minimum and maximum levels). It has no
hysteresis. Multiple channel selection will be combined
using the AND logic function of all channels selected.
PGOOD (%) = ^N------^-----L-V---S-t--Ba---r--g(--m-e--t--V-(--V-)----)^-----1---0---⁵-
Where N=1 to 63 for the PGood Max value, and N=1 to 62
for the PGood Min value. For example, with the target volt-
age of 1.5V and set point resolution of 2.5mV (LSB), the
Power Good Min and Max values can range from 0.17% to
10.50% respectively. A user can effectively double the
Power Good range by changing to the next higher output
voltage range setting, but at the expense of reduced set
point resolution.
Interrupt, Low VCC, Power OK and ResetOut signals can
only be forwarded to a single GPIO/PSIO.
In addition, the following are functions that are unique to
GPIO0 and GPIO1.
• HW Flags – these are hardware monitoring functions
forwarded to GPIO0 only. The functions include Under-
Voltage Lockout Warning, Over-Temperature Warning,
Over-Voltage Fault, Over-Current Fault and Over-Current
Warning for every channel. Multiple selections will be
combined using the OR logic selected function.
The Power Good minimum and maximum levels are
expressed as percentages of the target voltage.
A subset of hardware flags which includes Under-Voltage
Lockout Warning, Over-Temperature Warning, and Over-
Voltage Fault for every channel is available on the other I/
Os.
© 2014 Exar Corporation
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exar.com/XR77128
Rev 1A