adm1069ast-reel Analog Devices, Inc., adm1069ast-reel Datasheet - Page 12

• Manufacturer Part Number: adm1069ast-reel
• Description: Super Sequencer With Margining Control
• Manufacturer: Analog Devices, Inc.

ADM1069
POWERING THE ADM1069
The ADM1069 is powered from the highest voltage input on
either the positive-only supply inputs (VPn) or the high voltage
supply input (VH). This technique offers improved redundancy
because the device is not dependent on any particular voltage
rail to keep it operational. The same pins are used for supply
fault detection (discussed later in the Supply Supervision
section). A VDD arbitrator on the device chooses which supply
to use. The arbitrator can be considered an OR’ing of four
LDOs together. A supply comparator chooses the highest input
to provide the on-chip supply. There is minimal switching loss
with this architecture (~0.2 V), resulting in the ability to power
the ADM1069 from a supply as low as 3.0 V. Note that the
supply on the VXn pins cannot be used to power the device.
An external capacitor to GND is required to decouple the on-
chip supply from noise. This capacitor should be connected to
the VDDCAP pin, as shown in Figure 20. The capacitor has
another use during brownouts (momentary loss of power).
Under these conditions, when the input supply (VPn or VH)
dips transiently below V
immediately turns off so that it does not pull V
V
active until the next highest supply takes over the powering of
the device. A 10 μF capacitor is recommended for this
reservoir/decoupling function.
DD
capacitor can then act as a reservoir to keep the device
DD
, the synchronous rectifier switch
DD
down. The
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When two or more supplies are within 100 mV of each other,
the supply that first takes control of V
example, if VP1 is connected to a 3.3 V supply, V
to approximately 3.1 V through VP1. If VP2 is then connected
to another 3.3 V supply, VP1 still powers the device unless VP2
goes 100 mV higher than VP1.
VP1
VP2
VP3
VH
Figure 20. VDD Arbitrator Operation
COMPARATOR
SUPPLY
DD
IN
EN
IN
EN
IN
EN
IN
EN
keeps control. For
4.75V
4.75V
4.75V
4.75V
LDO
LDO
LDO
LDO
OUT
OUT
OUT
OUT
DD
VDDCAP
powers up
INTERNAL
DEVICE
SUPPLY