Walter
I sent you a model back in March of an ECL part that operated between Vcc =
2.0V and Vee = -0.5V. Could you please point out in that model the GND or
0.000V pin?
Because attachments are not allowed I'll copy relevant parts of the model
here.
[Pin] signal_name model_name R_pin L_pin C_pin
|
1 VCC POWER 1.000E-02 1.720E-09 4.240E-13
2 IN+ in 1.000E-02 1.720E-09 4.240E-13
3 IN- in 1.000E-02 1.720E-09 4.240E-13
4 CLK4+ clk4 1.000E-02 1.720E-09 4.240E-13
5 CLK4- clk4 1.000E-02 1.720E-09 4.240E-13
6 VEE POWER 1.000E-02 1.720E-09 4.240E-13
|
|****************************************************************
[Model] in
Model_type Input
Vinl = 350.000mV
Vinh = 550.000mV
C_comp 785.000fF 778.000fF 792.000fF
|
| variable typ min max
[Voltage Range] 2.00000V 2.000V 2.00000V
[POWER Clamp Reference] 2.00000V 2.000V 2.00000V
[GND Clamp Reference] -0.50000V -0.500V -0.50000V
[Temperature Range] 25 85 -40
[Model] clk4
Model_type Output_ECL
Vref=0.000E-01
Rref=5.000E+01
Cref=0.000E+00
Vmeas=0.450E+00
C_comp 1.430E-12 1.370E-12 1.450E-12
|
|
[Voltage Range] 2.000E+00 2.000E+00 2.000E+00
[POWER Clamp Reference] 2.000E+00 2.000E+00 2.000E+00
[GND Clamp Reference] -0.500E+00 -0.500E+00 -0.500E+00
[Pullup Reference] 2.000E+00 2.000E+00 2.000E+00
[Pulldown Reference] 2.000E+00 2.000E+00 2.000E+00
Are there designs that use split power delivery to ECL parts? Yes, I have
some test cards from a couple of ECL vendors that use the split rails for
their test. It allows the signal generator and scope they use in test to
remain at a 0.00V level, properly terminating the output and make the
correct DC measurements - no AC coupling required.
The Vref in the model is 0.00V. It is expressed this way because IBIS does
not allow equations for voltages. Vref is really Vcc - 2 V. To get around
this limitation [Model Spec] was invented so the Vref can show the proper
voltages for the three different corner cases. Likewise for Vinl and Vinh.
These voltages are really referenced to Vcc for an ECL input.
Describing where the current flows in a circuit tells you which power rails
will influence the input and output levels of the device. For the ECL
example, all the output currents flow in the Vcc rail, none flows in the Vee
rail. That tells you the output levels will track the Vcc supply. Varying
the Vee rail will not influence the output Hi or Low voltage. Varying Vcc
will change the output voltages.
For a CMOS device the current flows in Vdd when the part is high so the
output high is directly related to Vdd. Likewise current flows through the
Vss pin when the driver is low and any change in Vss will change the low
voltage. In a typical reflected wave switching CMOS net output high is not
a function of Vss but is directly affected by Vdd and output low is not a
function of Vdd but directly affected by Vss.
Regards,
Tom Dagostino
971-279-5325
tom@xxxxxxxxxxxxxxxxx
Teraspeed Labs
9999 SW Wilshire Street
Suite 102
Portland, OR 97225
-----Original Message-----
From: ibis-macro-bounce@xxxxxxxxxxxxx
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Walter Katz
Sent: Tuesday, July 12, 2016 9:43 AM
To: bob@xxxxxxxxxxxxxxxxx; IBIS-ATM
Subject: [ibis-macro] Re: Pin Reference Concerns
Bob,
Your whole discussion about ECL is a total obfuscation. Current flow is no
consideration on how to measure voltages at a buffer relative to a reference
node in the component. On slide 12 your statement " A VSS pin (GND DUT
connection) does not always exist" is totally incorrect. If there is not
such pin (GND DUT connection) how does the test fixture measure the voltages
at the I/O rail terminals? We MUST INSIST that all measurement be made close
to the buffer, at least inside of the component. This is a basic requirement
of any measurement of a buffer voltage.
Walter
-----Original Message-----
From: ibis-macro-bounce@xxxxxxxxxxxxx
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Bob Ross
Sent: Tuesday, July 12, 2016 12:33 PM
To: 'IBIS-ATM' <ibis-macro@xxxxxxxxxxxxx>
Subject: [ibis-macro] Pin Reference Concerns
All,
As a head's up, here is the presentation I plan to discuss at today's
meeting (July 12, 2016).
Bob
--
Bob Ross
Teraspeed Labs
http://www.teraspeedlabs.com
bob@xxxxxxxxxxxxxxxxx
Direct: 503-246-8048
Office: 971-279-5325
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