GTL2009 Datasheet, PDF (6/17 Pages) NXP Semiconductors – 3-bit GTL Front-Side Bus frequency comparator

Philips Semiconductors
GTL2009
3-bit GTL Front-Side Bus frequency comparator
8. Application design-in information
V_TT
R
2R
V_TT
56 Ω
common
front-side bus
V_DD
VREF
BO3
BO2
BO1
AO2
AO1
V_SS
1BI1
1BI2
1BI3
1AI
2AI
2BI1
2BI2
2BI3
Fig 3. Application diagram
PROCESSOR
A
slot A occupied
slot B occupied
PROCESSOR
B
002aaa998
8.1 Frequently asked questions
Question 1: When the GTL2009 is unpowered, the LVTTL inputs may be pulled up to
3.3 V and we want to make sure that there is no leakage path to the power rail under this
condition. Are the LVTTL inputs high-impedance when the device is unpowered and will
there be any leakage?
Answer 1: When the device is unpowered, the LVTTL inputs will be in a high-impedance
state and will not leak to V_DD if they are pulled HIGH or LOW while the device is
unpowered.
Question 2: What is the condition of the GTL and LVTTL output pins when the device is
unpowered?
Answer 2: The open-drain GTL outputs will not leak to the power supply if they are pulled
HIGH or allowed to float while the device is unpowered. The GTL inputs will also not leak
to the power supply under the same conditions. The LVTTL totem pole outputs, however,
are not open-drain type outputs and there will be current flow on these pins if they are
pulled HIGH when V_DD is at ground.
9397 750 13556
Product data sheet
Rev. 01 — 22 September 2005
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
6 of 17