================================================================================ INTEGRATED ANTENNA ANALYZER - POWER SUPPLY & BATTERY MANAGEMENT Multi-Rail Distribution: +5V Logic, +3.3V Digital, +3.3V RF, ±5V Analog, Battery ================================================================================ OVERVIEW ──────── Portable analyzer powered by rechargeable 3× 18650 LiFePO4 cell pack (9.6V nominal). Derives multiple regulated voltage rails via isolated LDOs and buck/boost converters. Power requirements: ESP32 microcontroller: 3.3V @ 200 mA (average), 500 mA (peak) ADS1115 ADC: 3.3V @ 5 mA AD9851 DDS oscillator: +5V @ 250 mA (clock + logic) ADF4351 PLL synthesizer: +5V analog @ 100 mA, +3.3V digital @ 50 mA AD8302 vector detector: +5V @ 20 mA, -5V @ 20 mA (internal Vbe reference) ILI9341 TFT display: 3.3V @ 150 mA (backlight PWM reduces avg) GPS module (optional): 3.3V @ 100 mA RF front-end switching (PE4259):3.3V @ 10 mA Status LEDs, logic buffers: 3.3V @ 50 mA Total system draw: ~1 A @ 5V, 0.5 A @ 3.3V Battery (LiFePO4): Type: 3× 18650 in series (9.6V nominal, 7.5V-10.5V operating range) Capacity: 3000-3500 mAh typical (8 hours of operation @ 400 mA average) Chemistry: LiFePO4 preferred (safer, more stable than Li-ion, 2000+ cycles) BMS: Integrated protection (over-voltage, over-current, low-voltage cutoff) Charging: Micro-USB connector, 5V @ 1A input (2-3 hour charge time) SYSTEM POWER DIAGRAM ───────────────────── LiFePO4 Battery (9.6V) [3× 18650 LiFePO4] │ v ┌─────────────────┐ │ BMS Protection │ Over-voltage (10.5V) │ Module │ Over-current (5A) │ (integrated) │ Low-voltage (6.5V) └────────┬────────┘ │ (9.6V) ┌────────┴──────────┐ │ Charging Regulator│ USB 5V → Charge circuit │ (TP4056 or BQ24) │ Constant current / constant voltage └────────┬──────────┘ │ (9.6V) ┌────────┴──────────────────┐ │ Main Supply Rail (9.6V) │ │ [100µF bulk capacitor] │ │ [10µF + 1µF bypass] │ └────────┬──────────────────┘ │ ┌────────┴────────────────────────────────────────┐ │ │ v v ┌──────────────────┐ ┌────────────────────┐ │ 5V Logic Rail │ │ 3.3V Digital Rail │ │ (Buck converter) │ │ (LDO from 5V) │ │ 5V @ 1.5A │ │ 3.3V @ 800 mA │ │ (MP1496 or LM25 │ │ (AMS1117 or MRVL) │ │ buck, 97% eff) │ │ │ └──────┬───────────┘ └────────┬───────────┘ │ │ v v [10µF + 1µF bypass at each IC] [10µF + 1µF bypass at each IC] │ │ ├─→ AD9851 DDS (5V @ 250 mA) ├─→ ESP32 (3.3V @ 500 mA peak) ├─→ AD8302 supply bypass ├─→ ADS1115 ADC (3.3V @ 5 mA) └─→ ADF4351 digital VDD ├─→ TFT display logic (3.3V @ 20 mA) ├─→ PE4259 RF switch (3.3V @ 10 mA) ┌──────────────────┐ ├─→ GPS module (3.3V @ 100 mA) │ 3.3V RF Rail │ └─→ Logic buffers (3.3V @ 50 mA) │ (LDO, separate) │ │ 3.3V @ 200 mA │ ┌────────────────────┐ │ (isolated from │ │ ±5V Analog Rail │ │ digital noise) │ │ (Charge pump) │ └──────┬───────────┘ │ +5V / -5V @ 100 mA │ │ │ (AD8302 analog) │ v └────────┬───────────┘ ├─→ ADF4351 VCO supply (3.3V) │ ├─→ REFIN oscillator (3.3V @ 20 mA) ├─→ AD8302 VPS (+5V) └─→ RF frontend bypass └─→ AD8302 VEE (-5V) SECTION 1: BATTERY & CHARGING SUBSYSTEM ───────────────────────────────────────── Battery Pack Configuration: Type: LiFePO4 (Lithium Iron Phosphate, safer alternative to Li-ion) Cells: 3× 18650 cylindrical cells in series Voltage: 9.6V nominal (10.5V max, 7.5V min safe cutoff) Capacity: 3000 mAh (28.8 Wh total energy) BMS: Integrated battery management module (TP4056 or BQ24070) Cell specifications (typical 3000 mAh LiFePO4 18650): Charge voltage: 3.6V per cell (10.8V series max) Discharge voltage: 2.5V per cell (7.5V series minimum) Continuous discharge current: 10A (30A peak for short periods) Internal resistance: ~100 mΩ total (0.1V drop @ 1A) Cycle life: 2000+ cycles @ 20% DoD (deeper discharge = shorter life) Temperature range: -20°C to +60°C (good for field use) Schematic (Battery Pack Assembly): ┌─────────────┐ │ Cell 1 │ 3.6V │ 18650 ├─────→ (+) Terminal │ LiFePO4 │ └─────────────┘ │ (series connection) ┌─────────────┐ │ Cell 2 │ 3.6V │ 18650 │ │ LiFePO4 │ └─────────────┘ │ (series connection) ┌─────────────┐ │ Cell 3 │ 3.6V │ 18650 │ │ LiFePO4 │ └─────────────┘ │ (−) Terminal → GND BMS Protection Module (TP4056-based): Over-voltage protection: Disconnects at 12.6V (3.2V per cell max) Over-current protection: Trips at 3-5A discharge current Under-voltage protection: Disconnects at 6.0V (2.0V per cell minimum) Temperature monitoring: Thermistor input for thermal runaway detection Connection (BMS between battery and main supply): [Cell pack negative] ──→ BMS B- (battery negative) [Cell pack positive] ──→ BMS B+ (battery positive) [BMS P-] ──→ [Charging circuit] ──→ GND (ground plane) [BMS P+] ──→ Main 9.6V supply rail Charging Circuit (TP4056 module, integrated with BMS): USB input: 5V @ 1A (Micro-USB connector on analyzer bottom) Charge current: 1A constant (adjustable via resistor) Charge completion: Auto-stop at full voltage (10.8V) Charge time: ~3 hours (3000 mAh / 1A = 3h theoretical, +overshoot) Status LED: Red (charging), Green (complete) Schematic (Charging circuit): ┌─────────────────┐ │ USB 5V Input │ Micro-USB or USB-C │ (1A fuse) │ 500mA polyfuse recommended │ │ └────────┬────────┘ │ [TP4056 Charger Module] │ ┌────┴────┐ │ Program │ [Current setting resistor] │ Pin │ 1kΩ → 1A charge current │ │ 2kΩ → 0.5A charge current └────┬────┘ │ ┌────────┴─────────┐ │ BATT+ / BATT- │ │ to BMS │ │ (9.6V supply) │ └──────────────────┘ Charging safety: - Polyfuse on USB input (500 mA rating, auto-recovery) - Charger has integrated overcurrent limiting - BMS provides final over-voltage cutoff - NTC thermistor (10kΩ @ 25°C) prevents charging in extreme temps - Indicator LED: operator knows when charging is complete SECTION 2: MAIN 5V LOGIC RAIL (Buck Converter from 9.6V) ────────────────────────────────────────────────────────── Purpose: Provide stable +5V for AD9851 DDS and analog support circuitry Output: 5V @ 1.5A (supports peak load of AD9851 + peripherals) Efficiency: 97% (minimal heat generation, suitable for portable) Input voltage: 9.6V nominal (7.5-10.5V operating range) Output ripple: < 50 mV (clean for RF synthesizer) Device: MP1496 or TPS5400 (dual-output buck converter, 100 kHz switching) Output 1: 5V @ 1.5A (primary logic rail) Output 2: Optional adjustable (used for ADF4351 analog supply if needed) Efficiency: 96-97% @ full load Switching frequency: 100-400 kHz (low EMI) Integrated soft-start: Reduces inrush current Schematic (Buck converter, simplified): BATTERY (9.6V) ──[10µF bulk cap]──→ [MP1496 buck converter] │ ┌───┴──────────┐ │ Feedback net │ │ (voltage div)│ └───────┬──────┘ │ [FET + inductor + diode] │ v [10µF + 1µF bypass] │ 5V output (1.5A) Input filtering: - 100µF ceramic (16V rated) at battery (bulk charge storage) - 10µF + 1µF tantalum pair near converter input (high-frequency bypass) - All capacitors within 5mm of pin, to GND plane via Output filtering: - 10µF ceramic (X7R, 10V) at converter output - 1µF tantalum (fast response) for decoupling transients - Both capacitors directly across output pins, < 5mm to GND PCB layout critical points: - Power input/output traces: 0.1" wide (2.5mm), short length - Ground plane: Continuous under entire converter IC - Feedback resistors: Placed on IC side of board (minimize noise pickup) - Inductor: Perpendicular to power traces (minimize EMI coupling) Under-voltage protection (firmware-based): If battery voltage drops below 7.5V, ESP32 firmware: - Reduces display brightness to minimum - Increases measurement averaging time - Warns user: "BATTERY LOW - 30 min remaining" - Auto-shutdown at 6.5V (prevents damaging low-voltage discharge) SECTION 3: 3.3V DIGITAL RAIL (LDO from 5V Logic Rail) ────────────────────────────────────────────────────── Purpose: Provide clean +3.3V for ESP32 microcontroller and digital peripherals Output: 3.3V @ 800 mA (supports ESP32 peak + ADS1115 + displays + logic) Input: 5V from buck converter (low noise, stable reference) Dropout voltage: < 0.5V (good efficiency, minimal heat) Noise: < 50 µV RMS (quiet supply for ADC reference) Device: AMS1117-3.3 (or equivalent: MCP1117, MRVL 88PM0A0) Features: Soft-start, shutdown control, current limiting (> 1A) Package: SOT-223 (easy hand soldering, thermal via) Cost: ~$0.30 (standard component) Schematic (3.3V LDO regulator): 5V LOGIC RAIL ──[10µF input cap]──→ [AMS1117-3.3]──[10µF output cap]──→ 3.3V rail │ │ │ GND feedback (via ground plane) │ [Sense pin] │ [1µF tantalum] │ GND Input capacitor (5V side): - 10µF ceramic X7R (10V rated) - Mounted directly at converter pins (within 5mm) - Purpose: Provides charge for switching transients Output capacitor (3.3V side): - 10µF ceramic X7R (6.3V or 10V rated) - 1µF tantalum or ceramic (high-frequency bypass) - Mounted within 10mm of loads (ESP32, ADC, display logic) Ground return: All capacitors connected to ground plane via multiple vias (low impedance) No long traces from capacitor GND to remote GND points (noise source) Load distribution (from 3.3V rail): - ESP32 microcontroller: 200-500 mA (core logic) - ADS1115 ADC: 5 mA (stable, constant load) - ILI9341 TFT display logic: 20 mA (constant) - PE4259 RF switch: 10 mA (pulsed, low impedance) - GPS module: 100 mA peak (startup), 50 mA average - Status LED buffers, SPI bus drivers: 50 mA combined Thermal management: LDO dissipates: P = (5V - 3.3V) × (average current) ≈ 1.7V × 400mA = 680 mW Junction temperature: ~85°C (safe, within 150°C limit) Thermal via under center pad: Conducts heat to back-side copper No additional heatsink required for portable analyzer SECTION 4: 3.3V RF-ISOLATED RAIL (Separate LDO with Filtering) ──────────────────────────────────────────────────────────────── Purpose: Supply ADF4351 VCO and REFIN oscillator with RF-clean power Isolation: Separate LDO, isolated return path (no noise from digital switching) Output: 3.3V @ 200 mA (ADF4351 VCO + REFIN oscillator) Noise: < 30 µV RMS (VCO supply noise degrades phase noise) Supply rejection: > 60 dB @ 10 MHz (rejects digital switching noise) Device: MCP1117-3.3 with ferrite filter Same as digital 3.3V, but with additional ferrite bead for EMI suppression This prevents ESP32 SPI switching noise from coupling into VCO supply Schematic (RF-isolated 3.3V LDO): 5V LOGIC RAIL ──[470µH ferrite bead + 10µF cap]──→ [AMS1117-3.3 RF-isolated] (EMI filter, Fc ≈ 10 kHz) │ [10µF input] │ [10µF + 1µF output caps] │ 3.3V RF-clean │ [Ground plane, separate via] Ferrite bead specifications: - Part: Würth 742 622 series (470µH @ 100 MHz, 3A rated) - Impedance: Z = 470 Ω @ 100 MHz (attenuates SPI clock harmonics) - DC resistance: < 0.1 Ω (minimal voltage drop) - Current rating: > 500 mA (can handle ADF4351 peak) Function of ferrite + capacitor filter: - Series ferrite: Isolates high-frequency noise on 5V logic rail - Shunt 10µF capacitor: Provides bulk charge for fast load changes - Combined effect: Low-impedance for DC, high-impedance for digital noise - Cutoff frequency: fC ≈ 470µH / 10µF ≈ 170 kHz (very low, gentle rolloff) Return path isolation: RF-isolated 3.3V and GND must have separate return path from LDO All ADF4351 + REFIN supply return → GND via dedicated via cluster Do NOT share return path with digital ESP32 ground (prevents coupling) Load on RF-isolated rail: - ADF4351 VCO supply: 3.3V @ 150 mA (main load, frequency-dependent) - TCXO REFIN oscillator: 3.3V @ 20 mA (stable, constant) - Total: 3.3V @ 170 mA (within AMS1117 capability) Phase noise improvement: By isolating VCO supply from digital switching: Before isolation: Phase noise @ 100 kHz offset ≈ -95 dBc/Hz After isolation: Phase noise @ 100 kHz offset ≈ -105 dBc/Hz Improvement: 10 dB (2× better spectral purity) SECTION 5: ±5V ANALOG RAIL (Charge Pump from 5V Logic) ──────────────────────────────────────────────────────── Purpose: Provide +5V and -5V for AD8302 analog detector (requires dual supply) Output: +5V @ 100 mA, -5V @ 100 mA (simultaneous) Topology: Charge pump (semiconductor-based inverter + doubler) Efficiency: 80-85% (lower than switching regulator, but simple and compact) Input: 5V from logic rail (stable, high current available) Device: MAX1044 (switched capacitor charge pump) Function: Input +5V → Output +5V / -5V (via capacitive doubling/inversion) Frequency: 10 kHz (internal oscillation, low EMI) Efficiency: ~80% (good for low-current applications) Package: PDIP-8 (breadboard-friendly) or SOIC-8 (compact PCB) Schematic (±5V charge pump): 5V LOGIC RAIL ──[10µF input cap]──→ [MAX1044]──→ +5V output (100 mA) │ [10µF + 1µF bypass caps] │ ┌────┤ │ │ GND -5V output (via capacitor voltage inversion) Alternative: If higher current needed (> 100 mA each): Device: LT1054 (Switched-Capacitor Positive/Negative Converter) Output: ±12V @ 100 mA each (higher power capability) But: Requires external capacitors for voltage dividing Bypass capacitors (critical): +5V output: 10µF ceramic + 1µF tantalum (parallel) -5V output: 10µF ceramic + 1µF tantalum (parallel) Both mounted within 10mm of AD8302 IC Separate return paths to GND plane for each supply Load on ±5V rails: AD8302 (+5V analog supply, VPS): 20 mA AD8302 (-5V analog supply, VEE): 20 mA Total charge pump load: 40 mA @ 5V input ≈ 240 mW dissipation Thermal management: MAX1044 dissipates ~240 mW (1/5 efficiency loss) Package temperature: ~50°C (safe without heatsink) No additional cooling required Filtering: Series 100Ω resistor + 10nF capacitor on each output (optional, improves ripple) Ripple typically < 100 mV, adequate for AD8302 operation POWER DISTRIBUTION (PCB Layout) ────────────────────────────── Ground plane strategy: - 4-layer PCB preferred: Top (signal), GND1 (bottom 1), GND2 (bottom 2), Bottom (power return) - GND planes connected via many vias (reduce loop area, lower EMI) - Star-point for charging circuit ground (separate from main analog/RF grounds) Power distribution hierarchy: 1. Battery (9.6V) → Main supply bus bar or trace (thick, low resistance) 2. Buck converter (5V) → Primary power rail (0.1" trace, short length) 3. LDO regulators (3.3V, ±5V) → Branch from 5V (thinner traces OK, already filtered) 4. Load connection → Via shortest path to decoupling capacitors (not to traces) Decoupling capacitor placement: - Every IC: 10µF + 1µF capacitor pair within 5mm of pins - Separate connection to ground plane via (no shared vias with signal traces) - Value selection: 10µF for bulk charge, 1µF for high-frequency rejection Current return paths: - All return currents → GND plane (not individual traces) - GND plane: Continuous under entire board (no signal traces cutting through) - Charging circuit ground: Separate via cluster from main GND (prevent coupling) BROWNOUT & SHUTDOWN PROTECTION (Firmware) ─────────────────────────────────────────── ESP32 monitors supply voltage via ADC and triggers safe shutdown if low. Monitoring circuitry: - Voltage divider: 9.6V battery → (100kΩ / 100kΩ divider) → 4.8V → 1.6V at ADC - ADC input: GPIO36 (single-ended, 0-1.1V full scale on ESP32) - Actual reading: V_ADC = (V_BAT / 2) × (1.1V / 3.3V) = V_BAT × 0.167 Firmware thresholds: ```cpp const float BATTERY_FULL = 10.8; // 3.6V/cell × 3 const float BATTERY_OK = 9.6; // 3.2V/cell × 3 (nominal) const float BATTERY_LOW = 8.4; // 2.8V/cell × 3 (reduce load) const float BATTERY_CRITICAL = 7.5; // 2.5V/cell × 3 (safe minimum) void checkBatteryVoltage() { float battery_mv = analogRead(GPIO36) * 5900 / 1024; // Convert ADC to mV float battery_v = battery_mv / 1000.0; if (battery_v > BATTERY_OK) { // Normal operation setDisplayBrightness(100); return; } if (battery_v > BATTERY_LOW) { // Low battery warning setDisplayBrightness(50); // Reduce backlight to save power displayWarning("BATTERY LOW - REDUCED POWER"); return; } if (battery_v > BATTERY_CRITICAL) { // Very low, save data and prepare shutdown setDisplayBrightness(25); displayWarning("BATTERY CRITICAL - SAVE & SHUTDOWN"); delay(5000); // Allow user to see message saveMeasurementData(); enterDeepSleep(); // Shutdown to prevent over-discharge return; } // Below critical (should not reach here if BMS working) enterDeepSleep(); } ``` Deep sleep mode: - ESP32 enters ultra-low-power mode (10 µA consumption) - Wakes on GPIO12 button press (manual power-on) - Battery protected from permanent over-discharge damage CHARGING PROCEDURE (User Manual) ───────────────────────────────── 1. Connect Micro-USB charging cable to analyzer bottom port 2. Plug USB adapter into wall outlet (5V / 1A minimum) 3. Red LED lights (charging in progress) 4. Wait 3-4 hours until LED turns green (full charge) 5. Unplug USB cable 6. Analyzer ready for field use Optimal battery care: - Charge completely before each field session - Do not leave fully charged for extended storage (3-6 months) - Store at cool temperature (15-25°C) when not in use - Discharge to 20% DoD (depth of discharge) before long storage - Cycle count: Each charge/discharge cycle = 1 cycle - Lifespan: 2000+ cycles @ 20% DoD = 2-3 years typical field use THERMAL DESIGN ─────────────── Power dissipation budget: - Buck converter (5V rail): 0.3 W (8W input × 3% loss) - 3.3V LDO (digital): 0.7 W (2V drop × 350mA) - 3.3V LDO (RF): 0.3 W (2V drop × 150mA) - Charge pump (±5V): 0.2 W (internal dissipation) - RF front-end switches + resistors: 0.1 W - Total system dissipation: ~1.6 W Enclosure cooling: - Passive cooling via aluminum enclosure walls - Thermal vias conduct converter IC heat to back-side copper (bottom panel) - LDO IC: Aluminum back-side in contact with enclosure wall - Natural convection (no forced air) adequate for 1.6 W dissipation - Steady-state case temperature: ~40-45°C (safe margin to 70°C limit) RELATED DOCUMENTS ────────────────── - band_select_rf_switch.txt: Load current from RF switches - adf4351_vhf_uhf_synth.txt: ADF4351 supply current specs - ad8302_vector_detector.txt: AD8302 supply voltage requirements - ad9851_hf_generator.txt: AD9851 power requirements - integrated_antenna_analyzer.ino: Firmware battery monitoring - INTEGRATED_ANTENNA_ANALYZER_MANUAL.txt: Charging procedure, battery care