CN101221587A - Method for reconstructing ground clamp curve and electric power clamp curve of chip IBIS model - Google Patents

Abstract

The invention discloses a method of reconstructing the ground clamping curve and the power clamping curve of a chip IBIS model, which reconstructs the current-voltage curve of the IBIS through a simple circuit model and is applicable to the signal integrity analysis and circuit simulation technical field. According to the characteristics showed by the power clamping curve and the ground clamping curve, proper discrete components mainly involving diodes and resistors are selected to build different equivalent circuits, and then the simulation of the equivalent circuits is carried out to obtain the accurate ground clamping curve and the power clamping curve of the IBIS model. The method which is simple and easy enables an engineer to carry out accurate simulation before obtaining the accurate IBIS model.

Description

The method that chip IBIS model ground clamper curve and power supply clamper curve are rebuild

Technical field

The present invention relates to a kind of printed board emulation mode, particularly a kind of IBIS model emulation method of IC chip.

Background technology

In IC chip application and emulation technology, the IBIS model is a kind of method to IO buffer modeling quick and precisely based on i-v curve (IV curve), be reflection chip drives and a kind of international standard that receives electrical specification, it provides a kind of standard file format to write down as drive source output impedance, parameters such as rising, fall time and input load are fit to the calculating and the emulation of high frequency effects such as doing ring and crosstalk very much.IBIS is a kind of simple and direct file layout, and it provides the behavior description of driver and receiver, but the in-built intellecture property details of leakage circuit not.Because IBIS is a simple model, during as simple bringing onto load emulation, to save 10 to 15 times calculated amount than corresponding full SPICE triode level model emulation.

It is high level and low level state that IBIS provides two complete IV curves to represent driver respectively, and under the slewing rate of determining the state exchange curve.The effect of IV curve is protection diode, TTL totem drive source to be provided and to penetrate the modeling ability that level is followed nonlinear effects such as output for IBIS.

The IBIS model is with its quick response, and the characteristics of data confidentiality become each IC design main flow reference model that manufacturer provided day by day in PCB emulation field.The channel that common IBIS obtains is to design manufacturer by corresponding IC to provide, and IC design manufacturer adds desired load according to the PSPICE or the HSPICE model of chip, extracts the IBIS model that the IV curve offers the client or carries out high-speed simulation with formation.Because each client's the circuit structure and the otherness of condition of work, also have the inaccuracy of the IBIS model that IC design manufacturer provides, caused many simulation results and real work result to greatly differ from each other, weakened the directive function of emulation greatly to designing.The step that the IBIS model is verified and checked all depends on IC design manufacturer to a great extent at present, and general eda software mainly concentrates on the dull consistance of syntax check and IV curve the inspection error correction scope of IBIS model.

Summary of the invention

The technical problem to be solved in the present invention provides the method that a kind of chip IBIS model ground clamper curve is rebuild, and can rebuild to obtain clamper curve accurately the IBIS model that IC producer provides.

For solving the problems of the technologies described above, the method that chip IBIS model of the present invention ground clamper curve is rebuild, comprise ground clamper curve fitting, make up the equivalent electrical circuit of a diode serial resistance, this equivalence circuit is carried out spice emulation obtain the new ground clamper curve of its i-v curve as described IBIS model.

Described diode door voltage is original place clamper knee point corresponding voltage.

Described resistance R g is the slope of original place clamper curve bend section, presses following formula and determines: $\mathrm{Rg}=\frac{\mathrm{\ΔVg}}{\mathrm{\ΔIg}}=\frac{\mathrm{Vg}-\mathrm{Vtg}}{\mathrm{Ig}-\mathrm{Itg}},$ Vtg wherein, Itg is the electric current and voltage value of flex point correspondence in the clamper curve of original place, Vg, Ig are any point voltage of original place clamper curve bend section linear segment.

The ball bearing made using that the present invention combines by independent component is come Simulation with I BIS model, and rebuilds its ground clamper curve on this basis, can obtain more accurate IBIS model, improves the confidence level and the authenticity of simulation result.

Another technical matters that the present invention will solve provides the method that a kind of chip IBIS model power supply clamper curve is rebuild, and can rebuild to obtain accurate power supply clamper curve the IBIS model that IC producer provides.

For solving the problems of the technologies described above, the method that chip IBIS model of the present invention ground clamper curve is rebuild comprises power supply clamper curve fitting, make up the equivalent electrical circuit of a diode serial resistance, this equivalence circuit is carried out spice emulation obtain the new power supply clamper curve of its i-v curve as described IBIS model.

Described diode door voltage is former power supply clamper knee point corresponding voltage.

Described resistance R p is the slope of former power supply clamper curve bend section, presses following formula and determines: $\mathrm{Rp}=\frac{\mathrm{\ΔVp}}{\mathrm{\ΔIp}}=\frac{\mathrm{Vp}-\mathrm{Vtp}}{\mathrm{Ip}-\mathrm{Itp}},$ Vtp wherein, Itp is the electric current and voltage value of flex point correspondence in the former power supply clamper curve, Vp, Ip are any point voltage of former power supply clamper curve bend section linear segment.

The ball bearing made using that the present invention combines by independent component is come Simulation with I BIS model, and rebuilds its power supply clamper curve on this basis, can obtain more accurate IBIS model, improves the confidence level and the authenticity of simulation result.

Description of drawings

Fig. 1 is an IBIS structure of models synoptic diagram;

Fig. 2 is the original place clamp current voltage curve that the embodiment of the invention relates to;

Fig. 3 is the former power supply clamp current voltage curve that the embodiment of the invention relates to;

Fig. 4 is the ground clamper match circuit diagram that secondary is rebuild in the embodiment of the invention;

Fig. 5 is the power supply clamper match circuit diagram that secondary is rebuild in the embodiment of the invention;

Fig. 6 is the new ground clamp current voltage curve that obtains in the embodiment of the invention;

Fig. 7 is the new power supply clamp current voltage curve that obtains in the embodiment of the invention.

Embodiment

The present invention is further detailed explanation below in conjunction with accompanying drawing.

Main conception of the present invention is the IBIS model that is provided according to IC manufacturer, release some basic parameters, select for use appropriate discrete component to construct the Buffer model in view of the above, carry out spice emulation improves simulation result with the method for the i-v curve (IV curve) that obtains more accurate IBIS model confidence level and authenticity.

Model to the pin behavior description in the IBIS model is mainly three kinds: output BUFFER, and input BUFFER, IOBUFFER can also be subdivided into I/O_open_sink, I/O_open_drain etc. again according to the difference of structure.And the most basic data of these buffer are exactly two: IV curve, V-t curve.The time domain response and the voltage transmission waveform of signal described in emulation according to the data and curves of these BUFFER.

The IV curve is divided into four kinds again, on draw (pull up) curve, drop-down (pull down) curve, clamper (ground clamp) curve and power supply clamper (power clamp) curve.These curves can be provided by manufacturer, also can obtain by SPICE emulation.Fig. 1 is IBIS structure of models figure, has identified corresponding respectively components and parts and reference voltage pullup reference, power clamp reference, pulldown reference and the ground clamp reference of these curves.

The method of obtaining power supply clamper curve and ground clamper curve by SPICE emulation is as shown in the table:

Power supply clamper curve	1, forbid tested buffer.2, between Vcc and output pin, place a direct voltage source Vin 3, allow Vin change between the 2*Vcc at-Vcc, write down the electric current I (Vpin) of every some correspondence
		The ground clamper	1, forbid tested buffer.2, between Gnd and output pin, place a direct voltage source Vin

Curve

3, allow Vin change between the 2*Vcc at-Vcc, write down the electric current I (Vpin) of every some correspondence

As an example the method that invention is provided is set forth with the IO buffer in the K9K8G08U1M chip of Samsung company production now.

The essential information of this IO buffer is as follows:

[Model] IO

Model_type I/O

Polarity Inverting

Vinl＝0.7200V

Vinh＝2.1600V

Vmeas＝1.6500V

Cref＝50.0000pF

Rref＝0.000

C_comp -8.2890pF 7.4600pF 9.1190pF

[Temperature Range] 25.0000 90.0000 -40.0000

[Voltage Range] 3.3000V 2.7000V 3.6000V

Pullup reference and power clamp reference are VCC (3.3V), and pulldown reference and ground clamp reference are Ground (0V).These data also can electrical specification partly obtain from the databook of this element.

Computing formula between the voltage that voltage that writes down in the IV curve of IBIS model and device pin test obtain is:

V _table＝V _reference-V _out

Therefore, can draw:

$V_{{\mathrm{powerclamp}}_{\mathrm{table}}}=V_{\mathrm{reference}}-V_{\mathrm{out}}=3.3-V_{\mathrm{out}}$

$V_{{\mathrm{groundclamp}}_{\mathrm{table}}}=V_{\mathrm{reference}}-V_{\mathrm{out}}=-V_{\mathrm{out}}$

Wherein, V _TableMagnitude of voltage on the expression IV curve map,

V _ReferenceThe magnitude of voltage of representing each curve institute reference,

V _OutMagnitude of voltage on the expression device pin,

V _{Powerclamptable}Magnitude of voltage in the expression power supply clamper curve,

V _{Groundclamptable}Magnitude of voltage in the expression ground clamper curve.

The original ground clamper curve of the K9K8G08U1M chip that Samsung company is provided and power supply clamper curve, as shown in Figures 2 and 3.Ground clamper curve and power supply clamper curve are made up of two sections line segments, and the joining of these two sections line segments is called flex point.According to the diode door voltage (claiming dead band voltage again) in the constructed equivalent electrical circuit of the present invention is original ground clamper curve or power supply clamper knee point corresponding voltage.In this example, above-mentioned two knee voltages are 0.5V, so the diode turn-on voltage that corresponding equivalent electrical circuit is chosen is 0.5V.

Owing to is to build as the match circuit with discrete component in the method provided by the present invention, and what utilize is the forward conduction characteristic of diode, and the diode of selecting for use can be divided into silicone tube and germanium tube according to the material difference, its threshold voltage normally: silicone tube V _ThBe about 0.5V, germanium tube V _ThBe about 0.1V.Selected diode door voltage is ground clamper curve and power supply clamper point of inflexion on a curve in the concrete equivalent electrical circuit of setting up by method provided by the present invention.

In the equivalent electrical circuit, the big or small computing formula of resistance in series is as follows:

$R=\frac{\mathrm{\ΔV}}{\mathrm{\ΔI}}=\frac{V-V_T}{I-I_T}$

V wherein _T, I _TBe the electric current and voltage value of flex point correspondence, V, I are any point voltage of curve linear part.

Clamper curve over the ground, according to the aforementioned calculation formula, resistance R g presses following formula and determines in the equivalent electrical circuit: $\mathrm{Rg}=\frac{\mathrm{\ΔVg}}{\mathrm{\ΔIg}}=\frac{\mathrm{Vg}-\mathrm{Vtg}}{\mathrm{Ig}-\mathrm{Itg}},$ Vtg wherein, Itg is the electric current and voltage value of flex point correspondence in the clamper curve of original place, Vg, Ig are any point voltage of original place clamper curve bend section linear segment.

Concerning power supply clamper curve, according to aforementioned computing formula, resistance R p presses following formula and determines in the equivalent electrical circuit: $\mathrm{Rp}=\frac{\mathrm{\ΔVp}}{\mathrm{\ΔIp}}=\frac{\mathrm{Vp}-\mathrm{Vtp}}{\mathrm{Ip}-\mathrm{Itp}},$ Vtp wherein, Itp is the electric current and voltage value of flex point correspondence in the former power supply clamper curve, Vp, Ip are any point voltage of former power supply clamper curve bend section linear segment.As previously mentioned, original place clamper curve or former power supply clamper curve generally can obtain from IC manufacturer, perhaps obtain by SPICE emulation.

In fact R is exactly the slope of response curve linear segment.From original ground clamper curve and power supply clamper curve observation or from the IBIS text or consult databook electrical specification part as can be known:

V _T=0.5000V, I _T=1.7510mA, optional again 1 V=3.0000, I=0.2363A,

The substitution formula calculates:

$R=\frac{\mathrm{\ΔV}}{\mathrm{\ΔI}}=\frac{V-V_T}{I-I_T}=\frac{3.0-0.5}{0.2363-0.001751}=\frac{2.5}{0.234549}=10.65875\mathrm{\Ω}$

Selected diode is 4148 types, is the PSPICE model parameter of selected diode below, and wherein Vj=.5 shows that the threshold voltage of this diode is 0.5V, is silicone tube.Its parameter is: .model D1N4148_1D (Is=2.682n N=1.836 Rs=.5664 Ikf=44.17m Xti=3Eg=1.11 Cjo=4p+ M=.3333Vj=.5Fc=.5Isr=1.565n Nr=2Bv=100 Ibv=100uTt=11.54n)

*TELEFUNKEN pid＝dln4148 case＝D035*91-08-20dsq

Fig. 4 be ground clamper curve correspondence equivalent electrical circuit its form by a diode and a resistance R g polyphone; Fig. 5 is the equivalent electrical circuit of power supply clamper curve correspondence, and it is made up of another diode and another resistance R p polyphone.Fig. 6 and Fig. 7 are respectively the result of Fig. 4 and two equivalent electrical circuit emulation of Fig. 5.New ground clamper curve and Fig. 2 that Fig. 6 is represented represent that the original place clamper curve that Samsung company provides compares, and as can be seen, the degree of fitting of these two curves is very approaching, can satisfy the requirement of emulation.The original place clamper curve that the Samsung company that the new power supply clamper curve that Fig. 7 is represented and Fig. 3 represent provides compares, and also as can be seen, the degree of fitting of these two curves is very approaching.

The invention discloses a kind of method of using the IV curve of ball bearing made using model reconstruct IBIS, be applicable to signal integrity analysis and simulation technology field, the characteristics that showed according to power supply clamper curve and ground clamper curve, select suitable discrete component to build different equivalent electrical circuit, then this equivalence circuit is carried out emulation and obtain the clamper of the power supply accurately curve and the ground clamper curve of IBIS model.This method is simple, can be so that the slip-stick artist can not carry out emulation accurately when obtaining accurate IBIS model.

Claims (6)

1.-plant the method that chip IBIS model ground clamper curve is rebuild, comprise ground clamper curve fitting, it is characterized in that, make up the equivalent electrical circuit of a diode serial resistance, this equivalence circuit is carried out spice emulation obtain the new ground clamper curve of its i-v curve as described IBIS model.

2. the method that chip IBIS model according to claim 1 ground clamper curve is rebuild is characterized in that described diode door voltage is original place clamper knee point corresponding voltage.

3. the method that chip IBIS model according to claim 1 ground clamper curve is rebuild is characterized in that described resistance TRg is the slope of original place clamper curve bend section, presses following formula and determines: $\mathrm{Rg}=\frac{\mathrm{\ΔVg}}{\mathrm{\ΔIg}}=\frac{\mathrm{Vg}-\mathrm{Vtg}}{\mathrm{Ig}-\mathrm{Itg}},$ Vtg wherein, Itg is the electric current and voltage value of flex point correspondence in the clamper curve of original place, Vg, Ig are any point voltage of original place clamper curve bend section linear segment.

4. the chip IBIS model power supply clamper curve method of rebuilding, comprise power supply clamper curve fitting, it is characterized in that, make up the equivalent electrical circuit of a diode serial resistance, this equivalence circuit is carried out spice emulation obtain the new power supply clamper curve of its i-v curve as described IBIS model.

5. the method that chip IBIS model power supply clamper curve according to claim 4 is rebuild is characterized in that described diode door voltage is former power supply clamper knee point corresponding voltage.

6. the method that chip IBIS model power supply clamper curve according to claim 4 is rebuild is characterized in that described resistance R p is the slope of former power supply clamper curve bend section, presses following formula and determines: $\mathrm{Rp}=\frac{\mathrm{\ΔVp}}{\mathrm{\ΔIp}}=\frac{\mathrm{Vp}-\mathrm{Vtp}}{\mathrm{Ip}-\mathrm{Itp}},$ Vtp wherein, Itp is the electric current and voltage value of flex point correspondence in the former power supply clamper curve, Vp, Ip are any point voltage of former power supply clamper curve bend section linear segment.

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