MacBook Air M2 A2681

Technical Specifications

Voltage Rails

Keyboard Daughter Board Rails (820-02862)

Power Tree

Keyboard Daughter Board Power Architecture

MLB B2B CONNECTOR (J0301 - 516S00457)
├── PP5V_S2_BKLT [5.0V] ────────────────────────────────┐
│   └── UT000 LP8548B1 (Keyboard Backlight Driver)
│       ├── PPVOUT_KBBL_REG [~22V] → J1101 LED Connector
│       └── KBDLED_CATHODE1/2 → LED current sink
│
├── PP3V8_AON_IPD [3.8V] ───────────────────────────────┐
│   ├── UT600 LM3638A0 (16V Boost)
│   │   └── PP16V0_TOUCHID [16.0V] → Touch ID sensor
│   ├── UT610 NCP160 (3.0V LDO)
│   │   └── PP3V0_TOUCHID [3.0V] → Touch ID sensor
│   └── LR503 (Ferrite) → PP3V8_CODEC_VP
│       └── UR500 CS42L84A Audio Codec VDD_P
│
├── PP3V3_AON_KBD [3.3V] ───────────────────────────────┐
│   ├── JR0601 LAS Flex B2B Connector
│   └── UT103 SLG4AP4815V (RSLOC Reset)
│
├── PP3V3_S2SW_IPD [3.3V] ──────────────────────────────┐
│   ├── UT101 PCAL6416A (Keyboard IOX1)
│   ├── UT102 PCAL6416A (Keyboard IOX2)
│   └── UT106 353S02212 (1.8V LDO)
│       └── PP1V8_S2_KBD [1.8V] → IOX low-voltage I/O
│
├── PP1V8_AON_IPD [1.8V] ───────────────────────────────┐
│   ├── U2240 SN74AUP1G17 (LAS MISO buffer)
│   └── JR0601 LAS Connector power
│
├── PP1V8_AWAKE [1.8V] ─────────────────────────────────┐
│   ├── UT001 74AVC2T45 (PWM level shifter)
│   └── LR500/LR501 → PP1V8_CODEC_VA/VCP
│       └── UR500 CS42L84A VDD_A, VDD_CP
│
├── PP1V25_AWAKE_IO [1.25V] ────────────────────────────┐
│   └── LR502 → PP1V2_CODEC_VL_VD
│       └── UR500 CS42L84A VDD_IO, VDD_D
│
└── PP1V2_S2 [1.2V] ────────────────────────────────────┐
    ├── UT620 353S02212 (Touch ID 1.8V LDO)
    │   └── PP1V8_TOUCHID [1.8V] → Touch ID sensor
    ├── U2230 74AVC2T45 (LAS SPI level shifter)
    └── UR200 SN74AXC1T45 (LAS CS level shifter)

Key Components

Keyboard Daughter Board Critical ICs

ESD Protection Devices

Boot Sequence

System Power-On Sequence (Main Logic Board)

Touch ID Power Sequence (Keyboard Daughter Board)

Progressive Diagnostic Engine

No Power Diagnostic

A2681 No Power — Complete Diagnostic Flow

Initial Checks

1. MagSafe 3 LED Test:
   • Connect MagSafe 3 charger (67W or higher recommended)
   • LED should illuminate amber (charging) or green (charged)
   • No LED = power not reaching board or catastrophic short
   • Dim/flickering LED = possible short circuit drawing excessive current
2. Visual Inspection:
   • Remove bottom case (10× pentalobe screws)
   • Check for liquid damage indicators
   • Inspect all flex cable connections
   • Look for burnt components, discoloration

M2 Power Architecture Notes

820-02862 Keyboard Board No Function

If the main logic board powers on but keyboard/Touch ID/audio jack don't work:

1. Check J0301 B2B Connector:
   • This 56-pin IPEX connector carries all power and signals between MLB and keyboard board
   • Inspect for bent pins, corrosion, or debris
   • Verify firm seating on both ends
2. Measure Power Rails at J0301:
   • PP3V8_AON_IPD: Pins 3-4 — should be 3.8V
   • PP3V3_AON_KBD: Pins 59-60 — should be 3.3V
   • PP5V_S2_BKLT: Pins 57-58 — should be 5.0V (when system booted)
   • PP1V8_AON_IPD: Pins 23-24 — should be 1.8V

Common No-Power Causes (M2 MacBook Air)

Angle Sensor Issues

If suspected angle sensor issue:

1. Check for corrosion on JR0601 LAS flex connector (Page 6)
2. Verify PP1V8_AON_IPD and PP3V3_AON_KBD at JR0601
3. Check level shifters U2230, U2240, UR200 for damage
4. Clean any corrosion with isopropyl alcohol
5. If chip is corroded, it may need replacement with a programmed unit

No Backlight Diagnostic

A2681 No Keyboard Backlight — Diagnostic Flow

Keyboard Backlight Circuit (Page 9)

The keyboard backlight uses the UT000 (LP8548B1SQ-04) LED driver IC:

• Input Power: PP5V_S2_BKLT from J0301 pins 57-58
• Boost Output: PPVOUT_KBBL_REG (~22V) via LT000 inductor and DT000 diode
• PWM Control: KBD_BKLT_PWM_1V2 (from MLB) → UT001 level shifter → KBD_BKLT_PWM_3V3
• LED Output: KBDLED_KEYB1/KEYB2 (current sources) and KBDLED_CATHODE1/2 to J1101 connector

820-02862 No Keyboard Backlight — Component Check

Step-by-Step Diagnosis

1. Verify PP5V_S2_BKLT Input:
   • Measure at J0301 pins 57-58 or at CT010-CT012 (input capacitors)
   • Should be 5.0V when system is in S2 state (booted)
   • If missing: check J0301 connection, verify MLB S2 power delivery
2. Check KBDBKLT_EN Enable Signal:
   • Measure at UT000 pin 11 (EN)
   • Should go HIGH when backlight is commanded on
   • If always low: check MLB backlight enable signal through J0301
3. Measure Boost Output PPVOUT_KBBL_REG:
   • Measure at DT000 cathode or CT050-CT057 capacitor bank
   • Should be approximately 22V when enabled
   • If missing with enable high:
     • Check LT000 inductor (10µH, 2.4A) for open circuit
     • Check DT000 boost diode (PMEG6010ER)
     • Check UT000 IC for damage
     • Verify CT058 switch node desense capacitor (optional component)
4. Check PWM Signal Path:
   • KBD_BKLT_PWM_1V2 input at UT001 pin 3
   • KBD_BKLT_PWM_3V3 output at UT001 pin 7
   • RT000 (47K) pull-up resistor
5. Check LED Connector J1101:
   • 8-pin connector (FF14A-6C-R11DL-B-3H)
   • PPVOUT_KBBL_REG to LED anodes
   • KBDLED_CATHODE1/2 from LED cathodes
   • Check flex cable for damage

Backlight IC Current Limits

Liquid Damage Procedure

A2681 Liquid Damage — Assessment and Recovery

Keyboard Daughter Board Vulnerable Areas

Based on the 820-02862 schematic, these areas are most susceptible to liquid damage:

1. J0301 MLB B2B Connector (Page 3):
   • 56-pin connector carries all power and signals
   • Corrosion here affects entire keyboard subsystem
   • Clean pins thoroughly with isopropyl alcohol and soft brush
2. Touch ID Power Section (Page 5):
   • UT600/UT610/UT620 LDOs and boost converter
   • Small capacitors CT610-CT629 easily corroded
   • EMC filter components FLT600/FLT610/FLT620
3. LAS Bypass Section (Page 6):
   • JR0601 LAS flex connector
   • Level shifters U2230, U2240, UR200
   • Angle sensor issues cause boot problems
4. Audio Codec Section (Page 11):
   • UR500 CS42L84A codec IC
   • Multiple small bypass capacitors around codec
   • Audio jack flex connector J0601 (Page 12)
5. Keyboard IOX Section (Page 7):
   • UT101/UT102 PCAL6416A IO expanders
   • ESD diodes DZT110-DZT113
   • I2C lines I2C_KBD_SCL/SDA

Cleaning Procedure

1. Initial Inspection:
   • Photograph all damage before cleaning
   • Note corrosion locations for targeted repair
   • Check for damaged traces under components
2. Ultrasonic Cleaning:
   • Use ultrasonic cleaner with appropriate solution
   • 5-10 minute cycle at 40-45°C
   • Rinse with distilled water or IPA
3. Manual Cleaning:
   • Apply flux to corroded areas
   • Use soldering iron to reflow and clean pads
   • Remove corroded solder, apply fresh solder
   • Clean with IPA and brush
4. Drying:
   • Air dry or use warm air (not hot air station)
   • Ensure completely dry before testing
   • Check under microscope for remaining moisture
5. Component Inspection:
   • Check all capacitors for corrosion damage
   • Look for eaten traces under solder mask
   • Verify resistor values haven't drifted

Common Liquid Damage Scenarios

Short Circuit Methods

820-02862 Short to Ground — Diagnostic Methods

Method A: DC Injection

Use a bench power supply with current limiting to inject voltage into shorted rails and locate the faulty component by thermal detection.

Method B: Thermal Imaging

1. Apply DC injection as above
2. Use thermal camera (FLIR, Seek, etc.) to visualize heat
3. Shorted component will heat up rapidly
4. May need to remove shields for visibility

Method C: Divide and Conquer

For rails with multiple branches, systematically isolate sections:

1. Measure total resistance of shorted rail to ground
2. Remove components one at a time, starting with most likely:
   • Capacitors (most common short cause)
   • ICs (failed silicon)
   • Ferrite beads (if rail splits through them)
3. Re-measure resistance after each removal
4. When resistance returns to normal, last removed component was the short

Normal Resistance Values (Unpowered)

Measurement Points

Test Points (Page 13)

Required Tools

Related repair guides