Pumpkin UM-20, Руководство пользователя

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2111 Comprehensive Drive
Aurora, Illinois 60505
Phone: 630-851-4722
Fax: 630- 851- 5040
www.conwin.com
Specifications subject to change without notice. All dimensions in inches. © Copyright 2012 The Connor-Winfield Corporation
Section 2: Power & Ground Considerations.
2.1 Power Supply and Grounds.
All system designs have a power supply and
ground circuit that is shared by all of the components
on the board. The operation of one component can
affect the operation of other components that share
the same power supply and ground circuit.
2.2 Power Supply.
The goal of a system’s power supply is to maintain
a stable voltage within a specified range while
supplying sufficient current. While an ideal power
supply would maintain the same voltage for any
possible current draw, real world systems exhibit the
following behaviors:
• A change in current and its associated
noise caused by one device affects other
devices attached to the same power supply
net.
• A change in current draw affects the voltage
of the power net.
2.3 Typical Power Supply System.
A typical power supply circuit consists of the
following:
• Voltage regulators that maintain voltage
stability within a required range while
supplying sufficient current to all components
served.
• Bulk, decoupling and bypass capacitors.
• Power and supply circuit runners or power
supply planes for power distribution to
components.
• Local decoupling and bypass capacitors at
each supply sensitive component.
2.4 Power Supply Management.
Improper voltage regulation can result in instability
of many system components or complete system
failure.
Periods of insufficient power are often referred to
as “Brown-Outs”, where power supply voltage drops
to an insufficient level, or “Black-Outs” where power
supply voltages totally disappear for a period of time.
For the OCXO to power up and configure properly
on initial power-up, Vcc must exceed the maximum
power-on reset (VPOR) voltage in order for the device
to proceed with configuration and initialization. The
VCC voltage is internally monitored on power-up to
properly trigger the device configuration circuitry.
On subsequent brown-out conditions where the
device is not power-cycled (i.e., the supply voltages
are not take down to 0v), the Vcc voltage must be
taken down below the minimum VPOR voltage in
order to clear out the device configuration content.
Subsequently, the voltages must exceed the VPOR
voltage once again in order for the device to be
programmed with the new configuration.
A brown-out condition is defined by the Vcc rail
dropping below its respective data retention voltage
defined by the VRAM in the data sheet.
Please refer to the OCXO data sheet for the
minimum and maximum VPOR voltages and Data
Retention Voltages.
Prevent system malfunction during periods of
insufficient power supply voltage by using external
lower voltage detector logic and supply management
circuitry.
2.5 POR/BOR Operation.
The power-on reset occurs when the device is
started from a Vss level. The brown-out condition
occurs when a previously powered device drops
below a specified range.
The devices RAM retention voltage (VRAM) is lower
than the VPOR/VBOR voltage trip point. When VPRO/
VBOR < Vcc < 2.7V, the electrical performance of the
OCXO will NOT meet the data sheet specifications.
2.6 Power-on Reset.
When the device powers up, the device Vcc will
cross the VPOR/VBOR voltage. Once the Vcc voltage
crosses the VPOR/VBOR voltage the following will
occur:
• Volatile registers are loaded with
values form the corresponding
non-volatile registers.
• The TCONF register will load the factory
programming.
• The device is capable of Digital / Analog
operation.
Application Note
AN2093
Page 2
Revision
P01
Date 10 May 2013