PD61 IC
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Product Details
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PD61 DISPLAY BACKLIGHT DRIVER & LIGHT CONTROL IC GUIDE
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1. PRODUCT IDENTIFICATION & HARDWARE SPECIFICATIONS:
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- Part Number: PD61 (Top laser silkscreen marking: "PD61")
- IC Classification: Inductive Step-Up (Boost) Display Backlight & Light Control Driver IC
- Silicon Manufacturer: Samsung Semiconductor / Maxim Integrated Partner
- Package Type: WLCSP-12 / WLCSP-16 (Wafer-Level Chip Scale Package) / Micro-BGA
- Pin Count: 12 to 16 Solder Balls
- Input Supply Voltage (VIN): 2.7V – 4.8V DC (Connected directly to VPH_PWR / VBAT rail)
- Boost Output Voltage (VLED+): 16.0V to 28.0V DC (High-voltage output to drive series LED strings)
- Switching Frequency: 1.0 MHz to 1.2 MHz High-Frequency PWM Boost
- Maximum Output Current: Up to 25mA – 30mA per LED string channel
- Stencil Compatibility: Universal 0.12mm Backlight / PMIC Stencil
- Recommended Solder Paste: 183°C Leaded Solder Paste (Sn63/Pb37)
- Hot Air Rework Settings: 300°C – 320°C (Airflow: 35% – 45%)
2. CIRCUIT ARCHITECTURE & MOTHERBOARD ROLE:
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- High-Voltage Step-Up Regulation: Operates in conjunction with an external 10µH/22µH boost inductor
and Schottky diode to step up 3.8V battery voltage to 20V–28V for LCD backlight illumination.
- PWM & I2C Brightness Dimming: Interfaces with the Applications Processor (AP) display subsystem
to modulate LED brightness smoothly from 1% to 100% without visible screen flicker.
- Multi-Channel Current Sinking: Regulates return current on cathode lines (LED-1, LED-2) to ensure
uniform lighting across the entire screen panel.
- Over-Voltage & Open-Load Protection: Internal OVP clamps output voltage if the display flex cable
is disconnected while powered, preventing capacitor blowout.
- Compatible Smartphone Models:
* Samsung Galaxy A-Series: Galaxy A5000, Galaxy A5, Galaxy A7
* Samsung Galaxy S-Series: Galaxy S6 (G9200) and compatible sub-circuits
* Various mid-range Android devices utilizing dedicated inductive backlight drivers.
3. COMMON MOTHERBOARD FAULT SYMPTOMS:
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- No Display Light (Black Screen / Dark LCD): The phone boots fully, rings, vibrates, and touches
respond normally, but the screen has zero illumination (graphics visible only under bright torch).
- Half-Screen Dimming / Uneven Illumination: One cathode feedback channel (LED-) fails inside PD61,
causing one side or section of the backlight to stay dark.
- Boost Coil Burnout / Severe Heating: Internal switching MOSFET punctures to ground (0Ω), causing
the adjacent boost coil to overheat, discolor, and emit a burning smell.
- Instant Blackout on High Brightness: The display lights up normally at 20% brightness, but the
screen instantly blacks out as soon as the brightness slider is raised to 100%.
- Secondary Battery Drain (Leakage): Internal diode leakage draws 0.05A – 0.12A continuously from
the VPH line even with the display turned off.
4. STEP-BY-STEP DIAGNOSTIC & TESTING PROCEDURES:
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A. Cold Testing (Multimeter Diode Mode):
1. Unplug battery and remove the LCD display flex connector.
2. Set multimeter to Diode Mode.
3. Place RED probe on motherboard ground shield. Probe test points around PD61:
- VIN Input Capacitor: Normal reading is 380mV – 480mV.
- Boost Diode Anode (Inductor side): Normal reading is 380mV – 480mV.
- Boost Diode Cathode (VLED+ High-Voltage rail): Normal reading is 450mV – 600mV.
- LED Cathode Feedback lines (LED-1, LED-2): Normal reading is 550mV – 700mV.
4. Fault Diagnosis: If VLED+ cathode reads 000mV (short circuit), check the output filtering
capacitor, the Schottky diode, and PD61.
B. Hot Testing (Live Operating Voltage Check):
1. Connect battery and screen. Power on the device.
2. Check voltage on boost coil input: Must read 3.8V – 4.2V (VBAT/VPH_PWR).
3. Check voltage on boost diode cathode (VLED+ output):
* With screen OFF / sleep mode: Reads battery voltage (~4.0V).
* With screen ON (active backlight): Must instantly boost up to 18V – 28V DC.
4. Diagnostic Rule: If input voltage is 4.0V, enable signal (EN) is 1.8V, but output remains at
battery voltage (no boost), PD61 is dead or the boost coil is open.
5. REWORK, REBALLING & INSTALLATION GUIDELINES:
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- Masking & Shielding:
* Protect adjacent delicate components (processor, cameras, plastic FPC sockets) with heat-resistant
polyimide tape.
- Chip Removal:
* Apply a small dab of non-corrosive BGA flux around the chip perimeter.
* Set hot air station to 310°C with 40% airflow.
* Apply heat evenly in circular motions. Lift the IC vertically with fine-tip tweezers once solder melts.
- Cleaning & Pad Inspection:
* Clean PCB pads using a solder wick and 300°C soldering iron. Clean thoroughly with Isopropyl Alcohol.
* Always test the external boost coil and Schottky diode before soldering a new IC; if the coil is
discolored or open, replace it alongside PD61.
- Soldering (Installation):
* Apply a microscope-thin layer of flux. Align Pin 1 index dot precisely.
* Apply gentle hot air at 305°C until the solder balls melt and surface tension pulls PD61 into alignment.
* Allow PCB to cool naturally before testing display illumination.
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