Datasheet

The master device in a tracking group is defi ned as the device
that has the highest target output voltage within the group. This
master device will control the ramp rate of all tracking devices and is
not confi gured for tracking mode. All of the CTRL pins in the track-
ing group must be connected and driven by a single logic source. It
should be noted that current sharing groups that are also confi gured
to track another voltage do not offer pre-bias protection; a minimum
load should therefore be enforced to avoid the output voltage from
being held up by an outside force.
Voltage Margining Up/Down
The product can adjust its output higher or lower than its nominal
voltage setting in order to determine whether the load device is capa-
ble of operating over its specifi ed supply voltage range. This provides
a convenient method for dynamically testing the operation of the load
circuit over its supply margin or range. It can also be used to verify the
function of supply voltage supervisors. Margin limits of the nominal
output voltage ±5% are default, but the margin limits can be reconfi g-
ured using the PMBus interface.
Pre-Bias Startup Capability
Pre-bias startup often occurs in complex digital systems when current
from another power source is fed back through a dual-supply logic
component, such as FPGAs or ASICs. The product family incorporates
synchronous rectifi ers, but will not sink current during startup, or turn
off, or whenever a fault shuts down the product in a pre-bias condi-
tion. Pre-bias protection is not offered for current sharing groups that
also have voltage tracking enabled.
Group Communication Bus
The Group Communication Bus, GCB, is used to communicate
between products. This dedicated bus provides the communica-
tion channel between devices for features such as sequencing, fault
spreading, and current sharing. The GCB solves the PMBus data rate
limitation. The GCB pin on all devices in an application should be con-
nected together. A pull-up resistor is required on the common GCB in
order to guarantee the rise time as follows:
Output Voltage Sequencing
A group of products may be confi gured to power up in a predeter-
mined sequence. This feature is especially useful when powering
advanced processors, FPGAs, and ASICs that require one supply to
reach its operating voltage prior to another. Multi-product sequenc-
ing can be achieved by confi guring the start delay and rise time of
each device through the PMBus interface and by using the CTRL start
signal.
Voltage Tracking
The product integrates a lossless tracking scheme that allows its
output to track a voltage that is applied to the VTRK pin with no
external components required. During ramp-up, the output voltage
follows the VTRK voltage until the preset output voltage level is met.
The product offers two modes of tracking as follows:
1. Coincident. This mode confi gures the product to ramp its output
voltage at the same rate as the voltage applied to the VTRK pin.
2. Ratiometric. This mode confi gures the product to ramp its output
voltage at a rate that is a percentage of the voltage applied to the
VTRK pin. The default setting is 50%, but a different tracking ratio
may be set by an external resistive voltage divider or through the
PMBus interface.
Illustration of Output Voltage Sequencing.
t
V1
V2
VOUT
Illustration of Coincident Voltage Tracking.
t
MASTER
SLAVE
VOUT
Illustration of Ratiometric Voltage Tracking
t
MASTER
SLAVE
VOUT
OKDx-T/50-W12-C
50A Digital PoL DC-DC Converter Series
MDC_OKDx-T/50-W12-C.A04 Page 25 of 41
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