# Of GPU forecast transient state to emulate an analysis

[introduction] nowadays, graphical processing is unit (GPU) has one billion four hundred and ten million and sixty-five thousand four hundred and eight several transistor. As GPU of every generation new generation appear, the transistor amount in GPU increases ceaselessly, in order to improve processor performance. However, the addition of transistor amount also brings about power demand to show exponential growth, this makes contented transient state answers a standard to become more difficult.

Nowadays, graphical processing is unit (GPU) has one billion four hundred and ten million and sixty-five thousand four hundred and eight several transistor. As GPU of every generation new generation appear, the transistor amount in GPU increases ceaselessly, in order to improve processor performance. However, the addition of transistor amount also brings about power demand to show exponential growth, this makes contented transient state answers a standard to become more difficult.

The SIMPLIS simulator that the article demonstrated how to use SIMPLIS Technologies will forecast and optimize the power source behavior of next generation GPU, tall changeover rate asks and exceed 1 among them, the voltaic level of 000 A needs swifter transient state to answer.

Constant guide a time (COT) control

Of polyphase step-down converter constant guide a time (COT) framework replaced the error amplifier in compensating a network with high speed comparator (EA) . Output voltage (V OUT) detects through feedback resistor, and with referenced voltage (V REF) undertakes comparative. Fall when V OUT to under V REF when, high side MOSFET (HS-FET) guides. Of MOSFET guide telling time is fixed, this means converter to be able to come true below steady state constant frequency. If exist,load rank jumps twinkling to change, converter still can be shown raise its pulse rate, reduce output with limit ground next developing. However, below this kind of circumstance, nonlinear annulus road control can make annulus road is adjusted complication.

Graph 1 showed the COT that is used at swift transient state to answer is controlled.

Control of graph 1 COT realizes swift transient state to answer. Data: Odd a power source system

Must mix to the behavior of converter power supply network (PDN) undertakes accurate build a model, in order to emulate function of transient state step-down and test and verify all sorts of systems that are based on GPU, and need not experience endless, costly iteration process.

Power supply network (PDN)

PDN is comprised by the package that receives voltage and ground connection course repeatedly, include power source and ground connection plane layout, be used at power source stability go Ou capacitor, and join or coupling arrive advocate any other copper of power source course are characteristic. The main goal that PDN designs is to change voltage wave motion to ensure GPU moves normally.

Graph the 2 PDN frameworks that showed network of typical GPU power supply.

Graph the PDN framework of network of power supply of 2 typical GPU includes to join the component of voltage and ground connection course. Data: Odd a power source system

The component in PDN shows parasitism behaviour, for example the inductance of equivalent series connection of capacitor (ESL) and resistor of equivalent series connection (ESR) . Answering to the system when undertaking building a model, still must consider these parasitism element. Increase changeover rate to be able to produce more powerful high frequency harmonic. The resistor of PDN, inductor, capacitor (the syntonic return that RLC) component can produce design personnel to may not realize, the high frequency harmonic that its resonance frequency can magnify converter switch arises, cause accident converter behaviour thereby.

Watch 1 demonstrated artificial intelligence (the requirement of course of typical power source of AI) application.

Express the 1 number above to highlight the design standard that indicated power source course. Data: Odd a power source system

This analysis is to use evaluate board carry out, should evaluate board combined MP2891 of controller of 16 photographs number and 130 A, two-phase, blame to keep apart MPC22163-130 of module of type step-down power source. Evaluate board can amount to 2, 000 A (graph 3) .

Graph 3 evaluate board combined digital controller and module of step-down power source. Data: Odd a power source system

PCB builds a model

The complexity of power source and appearance of ground connection polygon and multilayer pile makes move computational resistor and inductance very hard from the hand in layout. Contrary, the scattering parameter of PCB (S parameter) can use extraction of Cadence Sigrity PowerSI, frequency limits comes for 0 MHz 700 MHz. Port defines as follows: Port the 1 perpendicular module that includes top; Port the 2 perpendicular MPC22163-130 module that include floor; Port 3 include capacitor join; Port 4 include the join with load.

Graph the port configuration with the S parameter specific need of 4 extraction PCB. Data: Odd a power source system

It is very important to allocate special port for capacitor join, because they are in,alleviate the fast twinkling that comes from GPU changes the effectiveness of the respect depends on amount and position. Different capacitor position can affect the S parameter of PCB, invalid fixed position can bring about transient state to alleviate the effect not beautiful and power efficiency are low. Normally, the proposal discharges capacitor, with reducing the difference of method length as far as possible, the syntonic frequency that requires according to satisfying place of target impedance norms will choose capacitance.

This PDN board the capacitor type that two kinds used to differ in the design: High capacity capacitor and MLCC capacitor. The parameter such as voltage, rated temperature and structural material can affect capacitor the frequency of effective filter wave. Accordingly, to optimize a design, the impedance curve that designs personnel to must use model of market total electric capacity to consider capacitor in emulate (see a picture 5) .

Graph model of capacitor of 5 equivalent high capacity and frequency answer the impedance curve that evaluates capacitor. Data: Odd a power source system

The C BYPASS in model of market total electric capacity, ESL and the frequency that ESR defined capacitor impedance are answered. Syntonic frequency (F O) , or impedance dot, can use formula (1) is affirmatory:

C (1 of × of L of √ of π of Fo = 1/2)

The main purpose of these capacitor is to be in bear manostat module (VRM) efficiency is low high frequency when maintain low impedance. Appear this kind inefficient because the effective bandwidth of VRM and phasic abundant are spent,be be in low frequency (<1MHz) . Accordingly, capacitor must filter is in except frequency the signal besides VRM bandwidth, normally limits arrives in hundreds of KHz between a few MHz, this meeting affects the operation of PDN.

Graph the 6 PDN impedance curves that showed a pattern, can divide for 3 area: Low frequency (0 MHz comes 1 MHz) , intermediate frequency (1 MHz comes 100 MHz) and high frequency (100 MHz above) . This kind of dependency considered to be in low frequency to be mixed to the VRM inside intermediate frequency limits only advocate board, transient state load brings to bear on in ball bar array (on BGA) connector.

Curve of impedance of graph 6 PDN showed 3 distinct frequency range. Data: Odd a power source system

Time domain is emulated with correlation

Transient state copy is to use SIMPLIS emulator to undertake really, SIMPLIS emulator is emulation software of circuitry of system of power source of a kind of switch, can realize COT control to wait nonlinear function. The SIMPLIS model of MP2891 number controller combined the S parameter of the PCB that before MPC22163-130 step-down module is mixed, extracts. Before using S parameter at SIMPLIS simulator to undertake transient state is analysed, the IdEM that must use Dassault Systems is S parameter changeover RLGC model.

Graph the 7 SIMPLIS models that showed MP2891 and MPC22163-130, among them S parameter regards series connection as inductor (L9 and L3) with resistor (R1 and R2) in adding a principle to pursue.

Model of graph 7 SIMPLIS undertakes to MP2891 and MPC22163-130 transient state is emulated. Data: Odd a power source system

SIMPLIS is emulated MP2891 number controller nonlinear transmit union of the photograph that build a model with accurate power, can accurate forecast advocate board the transient state behavior that go up. Graph the 8 comparison that showed SIMPLIS is emulated and the lab is measured, among them difference is 5 MV only.

Graph 8 SIMPLIS is emulated and the lab is measured between the difference that has 5 MV only. Data: Odd a power source system

Why should undertake transient state is emulated?

The article is in evaluate board on use heterogeneous controller and type of two-phase blame segregation are efficient module of step-down power source undertakes building a model to forecasting transient state to emulate. converter model and parameter of power supply network allow accurate prolapse of the performance that forecasts polyphase step-down converter, transient state and too strong.

Accordingly, can export the quantity of capacitor through decreasing and decide its are effective the position will in inchoate phase optimize processor design. In addition, if design standard happening change, accurate imitate can assess the impact of these change quickly, identify any potential problems.

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