Skill: PLL Datasheet Modeling -- Core (Phases 1-4)

Model a PLL IC from its datasheet or system specifications using Simulink building blocks from the Mixed-Signal Blockset (MSB) foundation library msbPllFoundation.

Companion file: modeling-pll-datasheet-validate.md covers Phases 5-9 (loop filter design, validation, measurement, iteration, pitfalls).

When to Use

• Modeling a PLL IC from its datasheet (extracting parameters, selecting architecture)
• Designing a frequency synthesizer from system specs (fVco, fRef, lock time, phase noise targets)
• Building a behavioral PLL model in Simulink using Mixed-Signal Blockset
• Validating phase noise performance against datasheet measurements
• Selecting between Integer-N, Fractional-N, or Dual Modulus PLL architectures

When NOT to Use

• Circuit-level PLL design (transistor-level VCO, charge pump schematic)
• PLL analysis without building a Simulink model (use estimatePLLPhaseNoise directly)
• Clock distribution or jitter cleaning (not frequency synthesis)
• Non-MSB PLL modeling (e.g., custom Simulink blocks without the Mixed-Signal Blockset)

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Workflow Directives (MANDATORY)

1. Gather specs ONE AT A TIME (MANDATORY — no exceptions) -- For ANY PLL or frequency synthesizer design request (spec-driven or exploratory), ask exactly ONE question per response. Do NOT list multiple questions or present a bulleted requirements checklist. This reduces cognitive load and makes the interaction conversational. Sequence:

   1. Output frequency (or frequency range)
   2. Reference frequency (flag if N > 200 — high in-band noise penalty)
   3. Architecture (Integer-N / Frac-N / auto — may be predetermined by N)
   4. Lock time target
   5. Phase noise / jitter / spur targets (or confirm "none")
   6. Charge pump current (offer typical value as default)
   7. VCO requirements (Kvco, phase noise profile — offer rule-of-thumb)
   8. Loop filter preference (order, BW override)
   9. Any other requirements?
   10. Save location (folder path for .slx and results)

   Rules:

   • Ask ONE question, wait for answer, then ask the next.
   • Skip questions already answered in the user's initial prompt.
   • Offer a sensible default in parentheses so user can just confirm.
   • After all specs are gathered, present the Design Plan (Directive 5, Step A).

2. Iterate autonomously ONLY when targets are NOT met -- If the first attempt PASSES with >3x margin, STOP. The BW formula already gives a good design — do NOT sweep BW or iterate "for completeness." Only sweep/iterate when the first attempt FAILS or margin is < 2x. When iteration IS needed, sweep parameters and re-simulate until met.

3. Report progress and generate HTML summary -- Print brief status per attempt (e.g., "BW=1MHz, PM=70 -> lock=5.2us X"). After ALL targets pass, generate an HTML report saved alongside the model. Required sections:

   Report contents (mandatory):

   • Summary box: pass/fail verdict with margin
   • Model screenshot: print(['-s' model], path, '-dpng', '-r150')
   • Architecture diagram (text-based)
   • Design parameters grid (fVCO, fRef, N, Icp, Kvco, filter type, etc.)
   • Loop filter component table with time constants (τ_z = R2·C2, τ_p3 = R3·C3)
   • Transfer function box: Z(s), G(s)=Icp·Kvco·2π·Z(s)/(N·s), H(s)=G/(1+G), plus key values: fc, PM, zero freq, pole freqs
   • Bode plots (open-loop + closed-loop): export from pllOpenLoopPlot/ pllCloseLoopPlot via exportgraphics(fig, path, 'Resolution', 150). Find figures by Tag: 'PllOpenLoopDynamicPlot', 'PllCloseLoopDynamicPlot'
   • Vctrl transient: plot from simOut timeseries with lock time marker
   • Simulation results table (spec vs measured)
   • Simulation config (solver, stopTime, holdOff, averages)
   • Session metrics: include [COST] and [DURATION] placeholders in the report footer. The user fills these in from the Claude Code UI after the task completes (visible at session end).

   How to export plots:

   pllOpenLoopPlot(Icp, Kvco, N, 0, R2, R3, 0, C1, C2, C3, 0);
   fig = findobj('Type','figure','Tag','PllOpenLoopDynamicPlot');
   exportgraphics(fig, fullfile(outDir,'open_loop_bode.png'), 'Resolution', 150);
   

   Use relative src="filename.png" paths in HTML. Open report with web(reportPath, '-browser').

4. Figures must be visible -- After simulation, call set(0,'DefaultFigureVisible','on') and ensure all plot figures have 'Visible','on'. Call drawnow to force rendering. The MCP MATLAB server defaults to Visible='off'.

5. Show progress on screen at each step -- At key milestones, print status:

   • Step A — Design plan: ASCII block diagram + params before building

     [PLL TB]──▶[PFD]──▶[CP]──▶[Loop Filter]──▶[VCO]──┐
        ▲                                               │
        └─────────────[Divider ÷N]◀─────────────────────┘
     

     Include: architecture, fRef, N, Icp, Kvco, Fc, PM, filter type, solver. When adding impairments, show updated diagram BEFORE implementing.
   • Step B — Filter + Bode: component values, then pllOpenLoopPlot/pllCloseLoopPlot
   • Step C — Sim start: Simulating Pass 1 (lock time)... StopTime=9µs
   • Step D — Results: Lock time = 2.1 µs (target < 3 µs) ✓ [1.4× margin]
   • Step E — Pass 2 (only if PN spec): offsets, measured vs target, pass/fail

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Prerequisites

• Access to the target PLL IC datasheet (PDF) -- OR basic specs (fVco, fRef, lock time)
• Mixed-Signal Blockset installed (provides msbPllFoundation library)
• Control System Toolbox (for estimatePLLPhaseNoise validation, R2026b+)

Entry Points

A. Datasheet-Driven (Full workflow, Phases 1-4)

Use when you have a PLL IC datasheet. Follow all phases below.

B. Spec-Driven (No datasheet)

Use when you have basic PLL specs but no datasheet. Follow Directive 1 to gather specs, then derive remaining parameters.

Parameter derivation rules:

N = fVco / fRef  (or P*N+S for dual modulus)
BW = min(12/t_lock, fPFD/10)  (capped at fPFD/10 for stability)
Kvco: fVco/50 typical if not specified (e.g., 6 GHz → 120 MHz/V)
Icp: 1-5 mA typical (higher Icp → wider achievable BW with smaller R2)
PM: 50° default (60° if adding 4th-order pole)

Architecture selection:

Condition	Architecture
N is integer, single prescaler	Integer N PLL with Single Modulus Prescaler
N is integer, need P/P+1 flexibility	Integer N PLL with Dual Modulus Prescaler
N is fractional, low spur requirement	Fractional N PLL with Delta Sigma Modulator
N is fractional, simple design	Fractional N PLL with Accumulator

DSM order selection (when using Frac-N DSM):

• Order 1: simplest, highest spurs at fPFD/denom
• Order 2: good balance for most designs
• Order 3-4: lowest spurs, but more quantization noise energy pushed to high offsets (requires adequate filter attenuation)
• Match datasheet DSM order if available; default to order 3

R-divider tradeoff (when fRef ≠ fComp):

• Using R-counter: fComp = fRef/R → N_eff = fVco/fComp = N×R
• In-band noise penalty: +20×log10(N_eff) — larger N hurts in-band PN
• Only use R > 1 when channel spacing requires it (fComp = channel step)

Spec-driven steps:

1. Gather specs (Directive 1) → present Design Plan (Directive 5, Step A)
2. If VCO PN data available: validate VCO standalone first (see below)
3. Select architecture block from msbPllArchitectures (Strategy A — DEFAULT)
4. Design loop filter:
   • N ≤ 50: CompSelectionMethod='Automatic' with Fc and Phi
   • N > 50 (P79): thirdOrderPassiveFilterDesign → CompSelectionMethod='Manual'
   • N threshold applies to effective N (including fractional part)
5. Build model, simulate, present results

VCO standalone validation (when PN data provided):

% 1. Create VCO testbench model
vcoModel = 'VCO_Validation';
new_system(vcoModel); open_system(vcoModel);
set_param(vcoModel, 'Solver', 'VariableStepDiscrete');
add_block('msbPllFoundation/Ring Oscillator VCO', [vcoModel '/VCO']);
add_block('msbPllMeasurements/VCO Testbench', [vcoModel '/VCO TB']);
add_line(vcoModel, 'VCO TB/1', 'VCO/1', 'autorouting', 'smart');
add_line(vcoModel, 'VCO/1', 'VCO TB/1', 'autorouting', 'smart');

% 2. Get PeriodJitter and CornerFrequency from PN data
[pJitter, cFreq] = msblks.VCO.estimatePhaseNoiseCore(fVco, Foffset, PN_dBc);
set_param([vcoModel '/VCO'], 'Fo', num2str(fVco), ...
    'PeriodJitter', num2str(pJitter), 'CornerFrequency', num2str(cFreq));

% 3. Simulate and compare to datasheet (accept ±3 dB)
sim(vcoModel);
ud = get_param([vcoModel '/VCO TB'], 'UserData');

Skip to Phase 4.0 (Strategy A assembly) after deriving parameters.

C. Tune Existing Model (Meet a new spec)

Use when the user provides an existing .slx model and wants to meet a target (lock time, phase noise, spurs) without rebuilding from scratch.

Workflow:

1. Probe — extract current params: Fc, Phi, N, OutputCurrent, Kvco, CompSelectionMethod, filter components via get_param
2. Check for PLL Testbench — if missing or PLL input unconnected, ASK the user for fComp (P104). Add a PLL Testbench if needed.
3. Baseline sim — sim(model), read get_param(tbBlk, 'UserData') for lock time, frequency, phase noise. This is the ONLY valid baseline (P103).
4. Identify the lever:
   • Lock time too slow → increase Fc (BW ≈ 12/t_lock)
   • Phase noise too high in-band → decrease Fc, increase Icp, or reduce N
   • Spurs too high → increase filter order or narrow Fc
5. Redesign — set new Fc (and Phi if needed), keep CompSelectionMethod='Automatic' so the block recomputes filter components
6. Re-simulate — read testbench UserData. Iterate until spec is met.
7. Report — before/after comparison with trade-off notes

Key rules:

• NEVER estimate lock time from Vctrl settling (P103)
• NEVER guess fComp from Fo/N or RefFreq param (P104)
• Cap Fc at fPFD/10 for stability
• Use lock_time ≈ 12/Fc only for initial sizing, then verify with testbench

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Availability Check (MANDATORY)

Before using ANY function or block, verify it exists. Check exist(func,'file') for key functions (thirdOrderPassiveFilterDesign, estimatePLLPhaseNoise, phaseNoiseMeasure, phaseNoiseToJitter) and exist(lib,'file')==4 for libraries (msbPllFoundation, msbPllMeasurements, msbPllArchitectures). If not found, do NOT use — skip dependent steps.

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Phase 1: Extract Datasheet Parameters

1.0 Reading the Datasheet PDF

Use MATLAB's extractFileText (never read PDFs directly with the Read tool):

pdfPath = 'path/to/datasheet.pdf';
txtContent = extractFileText(pdfPath);
txtPath = strrep(pdfPath, '.pdf', '_extracted.txt');
fid = fopen(txtPath, 'w'); fprintf(fid, '%s', txtContent); fclose(fid);
fprintf('Extracted %d characters to: %s\n', strlength(txtContent), txtPath);

1.1 Architecture Identification

Determine the PLL topology from the functional block diagram:

Question	Typical Options
Integer-N or Fractional-N?	Integer-only, Fractional with accumulator, Fractional with DSM
DSM order (if fractional)?	1st, 2nd, 3rd, 4th
Prescaler type?	Single modulus, Dual modulus (P/P+1)
Integrated VCO?	Yes / No (external)
Reference path?	Direct, with R counter, with doubler, with divider
Output dividers?	None, programmable divide chain
Feedback tap point?	Before output divider (VCO), after output divider

1.2-1.4 Detailed Parameter Extraction

See references/datasheet-extraction.md for the full parameter tables:

• 1.2: Core PLL parameters (PFD, CP, dividers, VCO, output stage)
• 1.3: Noise parameters (VCO PN, PNSYNTH, flicker, jitter, spurs)
• 1.4: Frequency plan worked example

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Phase 2: Select Assembly Strategy

Decision Tree (ALWAYS follow this)

START
  │
  ├─ Does the PLL topology match an msbPllArchitectures template?
  │   ├─ YES ──► Strategy A (Architecture block) ◄── DEFAULT
  │   └─ NO ───► Strategy B (Foundation blocks)
  │
  └─ Do you need EXTERNAL custom noise injection (BLWN, spur sources wired
     into the signal path OUTSIDE the PLL subsystem)?
      ├─ NO ───► Strategy A (Architecture block) ◄── DEFAULT
      └─ YES ──► Strategy A + editSystem (flatten, then inject)
                 OR Strategy B (if injection point is before CP or after VCO)

Strategy A is the default for ALL designs — spec-driven or datasheet-driven. Foundation blocks (Strategy B) are only needed when topology has no matching architecture template (e.g., dual-loop, injection-locked, external VCO with non-standard feedback).

Strategy	When to Use	Performance	Complexity
A: Architecture block	Default. Any standard Int-N, Frac-N, Dual-Modulus PLL	3.3x faster sim (65s vs 212s for 5 GHz PLL)	4 blocks, 4 connections
A + editSystem	Need to inject CP broadband noise or add custom impairments	Same speed until flattened	Flatten adds ~5 internal blocks
B: Foundation blocks	Non-standard topology, external VCO, dual-loop, or educational/visualization purposes	Baseline (slowest)	9+ blocks, 11+ connections

Probe-First Pattern (MANDATORY before set_param)

Before setting ANY block parameter, probe the mask to discover exact parameter names. Never guess parameter names from documentation or memory. See references/probing-simulink-models.md for the full probe workflow.

blk = [model '/PLL'];
m = Simulink.Mask.get(blk);
paramNames = {m.Parameters.Name};
fprintf('Available params (%d):\n', numel(paramNames));
cellfun(@(p) fprintf('  %s\n', p), paramNames);

This eliminates errors like using 'Icp' (wrong) instead of 'OutputCurrent' (correct), or 'DividerRatio' (wrong) instead of 'N' (correct).

2.1 msbPllArchitectures -- Pre-built PLL Templates (Strategy A)

Architecture Block	Topology	Divider Params
Integer N PLL with Single Modulus Prescaler	PFD->CP->LF->VCO->Single Prescaler	Nmin, N (integer) — set N FIRST
Integer N PLL with Dual Modulus Prescaler	PFD->CP->LF->VCO->Dual Prescaler	ProgramCounter(P), PrescalerDivider(N), SwallowCounter(S) — constraints: P > S > 0 (P105)
Fractional N PLL with Accumulator	PFD->CP->LF->VCO->Frac Divider (Accum)	N (fractional), Nmin
Fractional N PLL with Delta Sigma Modulator	PFD->CP->LF->VCO->Frac Divider (DSM)	N (fractional), Nmin, dsm (order)

Key promoted parameters (common to all):

Category	Parameters
VCO	Kvco, Fo, Amplitude, AddPhaseNoise, Foffset, PhaseNoise, PeriodJitter, CornerFrequency, FlickerExponent
Charge Pump	OutputCurrent, EnableCurrentImpairments, CurrentImbalance, LeakageCurrent, EnableTimingImpairments
Loop Filter	CompSelectionMethod(Automatic/Manual), Fc, Phi, FilterType, C1-C4, R2-R4, LfEnableImpairments, Temperature
PFD	DeadbandCompensation, EnableImpairments
Analysis	ol_opt, cl_opt, estimatePn
Probe	pfd_up_dn, cp_out, lf_out, ps_out

Built-in callbacks:

• msblks.PLL.editSystem(gcb) -- flatten to editable subsystem
• msblks.PLL.estimatePhaseNoise(gcb) -- analytical PN estimation
• msblks.VCO.plotMaskFigure(gcb) -- plot PN fit vs data

2.2 msbPllFoundation -- Individual Building Blocks (Strategy B)

See references/assembly-code.md for the full block table and parameters. Key blocks: PFD, Charge Pump, Loop Filter, Ring Oscillator VCO, Fractional Clock Divider with DSM.

2.3 Gap Analysis

Architecture blocks cover PFD, CP, LF, VCO, and Dividers. For R counter, ref doubler, RF output divider, or CP broadband noise: flatten with editSystem, then add custom blocks inside the subsystem.

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Phase 3: Create Custom Blocks / Customize Architecture

3.0 Flattening (msblks.PLL.editSystem)

Set all mask parameters FIRST, THEN flatten. After flattening, the subsystem contains individual blocks (PFD, CP, LF, VCO, Divider) that you can modify.

blk = [model '/PLL'];
set_param(blk, 'Kvco','40e6', 'Fo','4.225e9', 'OutputCurrent','5e-3', ...
    'N','422.52', 'CompSelectionMethod','Automatic', 'Fc','60e3', 'Phi','48');
msblks.PLL.editSystem(blk);  % Flatten AFTER setting params

3.1-3.4 Custom Block Recipes

See references/assembly-code.md for: CP broadband noise (3.1), reference path (3.2), RF output divider (3.3), feedback select mux (3.4).

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Phase 4: Assemble the Model

PERFORMANCE DIRECTIVE — Batch Model Assembly Execute the ENTIRE model assembly in ONE mcp__matlab__evaluate_matlab_code call (new_system, set_param, add_block, add_line, scope setup — ALL in one script). Each MCP round-trip = ~10-15s overhead. Batched = ~30s vs individual = 5+ min. Pattern: (1) compute params, (2) write assembly script to .m file in save folder, (3) execute via mcp__matlab__run_matlab_file (keeps terminal clean — no code dump), (4) verify. Using run_matlab_file instead of evaluate_matlab_code for large scripts prevents raw code from cluttering the user's screen during live demos.

4.0 Strategy A: Architecture Block Assembly (DEFAULT)

Architecture blocks: 3.3x faster sim, 56% fewer blocks, 64% fewer connections. Full assembly code template in references/assembly-code.md. Key sequence:

1. new_system + solver config (VariableStepDiscrete, ReturnWorkspaceOutputs='on')
2. add_block from msbPllArchitectures/<type>
3. Set divider: Nmin='1' first, then N, then Nmin to final value (P57/P92)
4. Set VCO params: Kvco, Fo, OutputCurrent, AddPhaseNoise, RefFreq
5. Loop filter: thirdOrderPassiveFilterDesign for N>50 (P79), else Automatic
6. PFD timing: PropDelay = max(50e-12, min(5e-12, 1/(2*fVCO)/10)), MaxFreqInterest = 2*fVCO (50ps floor — block rejects smaller values)
7. Enable lf_out='on' for Vctrl probe
8. Add PLL Testbench (Fo=fPFD, ExpectedFreq=fVCO, SampleRate=8*fVCO)
9. Set SpectralAverages='2' (P102: mask default is 4), LockTimeOption='on', PhaseNoiseOption='off' (P83)
10. StopTime = min(3*t_lock, 50e-6), HoldOffTime = min(1.5*estLock, 0.8*StopTime)
11. Set paired vectors via Simulink.Mask.get: PhaseNoiseFreqOffset, TargetPhaseNoiseVector (P71, P100: use -999 if no targets — mask rejects -inf)
12. Connect: TB/1→PLL/1, PLL/1→TB/1, PLL/2→Scope+ToWorkspace
13. Simulink.BlockDiagram.arrangeSystem(model); drawnow; set_param(model,'ZoomFactor','FitSystem'); drawnow; (P95)

4.1 Strategy B: Foundation Blocks

Use ONLY for non-standard topologies. See references/assembly-code.md.

4.2 Stability Analysis (ALWAYS before time-domain sim)

Confirm PM > 45° and no closed-loop peaking > 1 dB before running full sim.

• pllOpenLoopPlot(Icp,Kvco,N,Fc,R2,R3,R4,C1,C2,C3,C4) / pllCloseLoopPlot(...)
• For 3rd-order passive: R4=0, C4=0. See references/stability-analysis.md.
• If pllOpenLoopPlot crashes (ylim error at phase <= -180°): use manual Bode fallback per P106 — compute Z(s), G(s) via logspace sweep. Do NOT use Control System Toolbox (tf, bode) — it is not required.

4.3 Simulate and Read Results

simOut = sim(model);
delete(findall(0,'Type','figure','Tag','Msgbox_Warning'));
% Read lock time from PLL Testbench model workspace
sid = Simulink.ID.getSID([model '/PLL Testbench']);
sidParts = split(sid, ':'); sidSuffix = sidParts{2};
mdlWs = get_param(model, 'ModelWorkspace');
lockTime = evalin(mdlWs, ['LockTime_' sidSuffix]);
freq = evalin(mdlWs, ['Frequency_' sidSuffix]);

% Alternative: read from UserData (works after sim completes)
ud = get_param([model '/PLL Testbench'], 'UserData');
lockTime = ud.lockTime;  % seconds
freq = ud.freq;          % Hz
pnLevels = ud.phaseNoiseLevel; % dBc/Hz vector

P103: NEVER estimate lock time from Vctrl settling. The PLL Testbench uses frequency-error-based detection (FreqErrorTol) — this is the ONLY valid lock time measurement. Manual Vctrl analysis gives incorrect results.

P104: If the model has NO PLL Testbench or unconnected reference input, you CANNOT determine fComp. The RefFreq parameter is for PN estimation only — it does NOT define the actual reference clock. ASK the user for fComp before proceeding. Do not guess or calculate it from Fo/N.

Probe tab ports (after VCO out port 1): pfd_up, pfd_dn, cp_out, lf_out, ps_out. HoldOffTime must be < StopTime, otherwise no measurements.

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Quick Reference

f_PFD = f_REFIN*(1+D)/(R*(1+T))  |  f_VCO = f_PFD*(INT+FRAC/MOD)  |  f_OUT = f_VCO/RF_DIV
N_eff = INT+FRAC/MOD (from VCO)  |  N_eff = (INT+FRAC/MOD)*RF_DIV (from divider output)
In-band PN  = PNSYNTH + 10*log10(f_PFD) + 20*log10(N)
1/f PN at f = PN1_f + 10*log10(10kHz/f) + 20*log10(f_RF/1GHz)
Divider effect = -20*log10(RF_DIV) on output phase noise

Happy Path Cheat Sheet (Spec → Lock Time Verified)

Most common workflow in ~20 steps:

1. User gives: fVCO, fRef, lock time target
2. Derive: N = fVCO/fRef, Fc = 12/t_lock (cap at fPFD/10), Kvco = fVCO/50
3. Present Design Plan (block diagram + params)
4. Build model (ONE mcp call):
   - new_system, VariableStepDiscrete solver
   - add_block msbPllArchitectures/Integer N PLL...
   - set Nmin='1', N, Nmin=N
   - set Kvco, Fo, OutputCurrent, Fc, Phi='50'
   - add PLL Testbench (Fo=fRef, ExpectedFreq=fVCO, SampleRate=8*fVCO)
   - set LockTimeOption='on', SpectralAverages='2'
   - connect TB↔PLL, enable lf_out, add scope
   - StopTime = min(3*12/Fc, 50e-6), HoldOff = 1.5*12/Fc
   - arrangeSystem + FitSystem
5. Plot Bode: pllOpenLoopPlot(...), confirm PM > 45° (if ylim crash, use manual fallback P106)
6. sim(model)
7. ud = get_param(tbBlk, 'UserData'); lockTime = ud.lockTime;
8. Report: lock_time vs target, margin, PASS/FAIL
9. If margin > 3x → DONE. If not → increase Fc by 50%, repeat from step 5.

Library names (canonical): msbPllArchitectures, msbPllFoundation, msbPllMeasurements, msbUtilities

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