Mobile Phone IC For PMI632 (PM902) Original
The PMI632 (often identified in schematics as PM902 in specific device layouts) is a highly versatile, multi-functional Power Management Integrated Circuit (PMIC). Developed by Qualcomm, it serves as a sub-PMIC or companion chip, typically paired with a primary PMIC to offload specific high-current tasks like battery charging, display power, and flash LED management.
Found in dozens of popular mid-range devices from brands like Xiaomi, Samsung, Motorola, and Vivo, it is a cornerstone of the Snapdragon 400 and 600 series power architectures.
Technical Specifications: PMI632
| Feature | Specification Detail |
| Model Number | PMI632 (Variants: 902-00, 502-00) |
| Manufacturer | Qualcomm Technologies, Inc. |
| Package Type | BGA (Ball Grid Array) |
| Input Voltage ($V_{BUS}$) | $3.5\text{V} \text{ to } 12\text{V}$ (Supports Fast Charge) |
| Max Charging Current | $3.0\text{A}$ (Supports Quick Charge 3.0) |
| Display Support | Integrated LCD/OLED Bias Voltage (+/- Rails) |
| WLED Driver | 2-channel or 3-channel high-efficiency driver |
| Communication | SPMI (System Power Management Interface) |
| Flash/Torch Current | Up to $1.5\text{A}$ for Dual-LED configurations |
| Thermal Protection | Integrated over-temperature sensing and shutdown |
| Operating Temp | $-30\degree\text{C} \text{ to } +125\degree\text{C}$ |
Core Functional Blocks
The PMI632 is designed to handle “peripheral” power tasks that require high efficiency and precision.
1. Advanced Battery Charging (SMBC)
The PMI632 houses the Switch-Mode Battery Charger. It intelligently manages the transition between USB input power and battery output. It supports Qualcomm Quick Charge 3.0, utilizing an “intelligent negotiation” for optimum voltage ($INOV$) to minimize heat while maximizing charging speed.
2. Display Bias & Backlight
This IC is critical for visual output.
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LCD Bias: It generates the $V_{SP}$ and $V_{SN}$ (typically $+5\text{V}$ and $-5\text{V}$) required to drive the liquid crystal pixels.
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WLED Driver: It acts as a “boost converter” to jump battery voltage up to the $15\text{V} – 25\text{V}$ range needed to light up the display backlight string.
3. Flash & Haptics
To simplify motherboard design, the PMI632 includes integrated drivers for the Camera Flash and the Vibration Motor. This consolidation reduces the number of external components needed, saving valuable PCB space.
Diagnostic Signs of a Defective PMI632
Because the PMI632 sits between the charging port and the rest of the system, it is often the first component to fail during a power surge.
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“Fake Charging”: The phone shows the charging lightning bolt icon, but the battery percentage never increases or actually drops.
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No Display / No Backlight: If the phone vibrates and receives calls but the screen remains black, the WLED or Bias section of the PMI632 may be shorted.
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Dead Short ($V_{PH\_PWR}$): If a multimeter shows a short to ground on the main power rail, the PMI632 is a primary suspect.
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Boot Stuck at 0.01A: If a USB power meter shows a tiny, frozen current draw, the IC may be failing to hand off power to the main CPU.
Repair & Installation Notes
The PMI632 is a BGA chip that requires professional micro-soldering equipment.
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Alignment: Ensure the “Pin 1” marker on the IC aligns with the board’s corner markings.
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Heat Profile: Use a nozzle temperature of approximately 345°C with low airflow to avoid blowing away tiny surrounding resistors and capacitors.
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Reflow Tip: If a device has display flickering issues, sometimes a “reflow” (gently heating the chip until the solder liquefies and resettles) can fix cold solder joints caused by physical drops.
