This article walks you through the Samsung A03 full charging diagram step-by-step and gives a practical, technician-friendly troubleshooting checklist to solve common charging problems. The diagram being explained is the Samsung A03 Full Charging Diagram.
Samsung A03 - SM-A035F, SM-A037F
The Samsung A03 charging diagram shows the complete charging IC path, the VBUS input, the battery line, and the faulty components used for repair.
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| Samsung A03 Charging Schematic Diagram - Complete Repair and Solution |
☁ Quick overview:
At a glance, the charging diagram maps how external power (charger/cable) reaches the battery and how the phone’s protection and management circuits control charging. The main blocks you’ll see in the diagram are:
1. Charging connector / USB input (VBUS) — where 5V (or fast-charge voltage) enters.
2. Input filter & protection — ESD diodes, small capacitors, sometimes a choke or filter resistor.
3.Fuse / polyfuse / resistor — a protective element that can open or rise in resistance if shorted.
4.Charging/Power Management IC (PMIC) — the brain that negotiates charge current, handles battery charging algorithms, and monitors battery voltage & temperature.
5. Charging MOSFETs / switches — power transistors that direct current into the battery and isolate when needed.
6 . Battery protection/fuel gauge — a small IC or part of PMIC that monitors cell voltage, temperature, and cut-off.
7. Battery pack (Li-ion) — the final destination; typical resting voltage ~3.7V, full ~4.2V.
8 . Indicator circuitry / LEDs / charging LED — shows charging status.
Each of these blocks is visible and labelled in the Samsung A03 charging diagram. If you’re following the PDF diagram, you can trace the charging path from VBUS → protection → PMIC → MOSFETs → battery.
☁ Step-by-step explanation (follow the current):
1. Power arrives at the charging connector (VBUS):
When you plug a charger, 5V (or higher for fast charging) appears on the VBUS pin. The first elements after the jack are usually transient surge protectors (ESD diodes) and small capacitors to smooth spikes.
2. Input filtering and initial protection:
The diagram shows small RC/LC components and sometimes a diode to prevent reverse currents. These absorb spikes and protect the PMIC.
3.Fuse / PTC / resistor stage:
A polyfuse or small SMD fuse sits next. If a short happens downstream, this element opens and isolates. If it’s blown or high-resistance, charging can be intermittent or stop entirely.
4. Power management IC (PMIC) receives VBUS:
The PMIC negotiates the charging current, checks the battery voltage and temperature (via a thermistor), and engages the MOSFETs to allow current into the battery. In the diagram, this block is central — it has pins for VBUS, BAT, PROG (current sense), TEMP, and COMM (data lines).
5. Charging MOSFETs and current sense:
MOSFETs control the heavy current flow. A sense resistor (shunt) may sit in series to measure charging current — the PMIC reads voltage across it to regulate current.
6 . Battery & protection:
The battery connector leads to the cell. If a separate battery protection IC is present, it will cut off charging if the voltage, current, or temperature is out of safe ranges.
7. Status indicators & diagnostics:
LEDs or charging indicators are driven by GPIOs from the PMIC or the MCU. Test points near these allow technicians to read voltages and states.
☁ Expected voltages & test points (what to measure):
VBUS (charger pin): ≈5.0 V when normal USB; could be higher with fast chargers (9V, 12V depending on protocol).
PMIC input pin: same as VBUS (minus a small drop across protection).
BAT pin (when charging): between battery voltage (≈3.7 - 4.2 V) and float voltage (≈4.2 V).
Charging current sense node: small millivolt drops across shunt — interpreted by PMIC.
When diagnosing, always compare to these expected values at labelled test pads in the diagram.
☁ Common symptoms & targeted solutions:
↦ Symptom: Phone shows “Not charging” or very slow charging:
1 . Check the charger & cable first. Use a known good charger and cable. Rule out external causes.
2. Measure VBUS at the onnector. If no 5V appears, replace the cable or charger. If 5V is present but the phone is not charging, continue.
3. Check the input fuse/resistor. Use a multimeter in continuity/ohms mode — a blown fuse or high resistance indicates replacement is needed.
4. Inspect the charging port mechanically. Bent pins or loose port solder joints are common. Reflow or replace the connector if wobbly.
5. If VBUS reaches PMIC but no battery charging: PMIC might be damaged, or battery protection tripped.
↦ Symptom: Charging stops at ~50% or fluctuates:
Possible causes: bad battery cell, faulty battery temperature (thermistor open/short), or PMIC charging algorithm misreading.
Solution: Check battery voltage directly at battery pads; test thermistor resistance (refer to diagram, am temp pin). Replace the battery or PMIC as required.
↦ Symptom: Phone heats while charging:
Likely: excessive current due to shorted MOSFETs or a damaged battery.
Solution: Stop charging immediately. Measure current draw and inspect MOSFETs and the battery. Replace faulty parts.
↦ Symptom: Intermittent charging (plugs/unplugs):
Likely: loose solder joints on the charging port, cracked trace, or bad ground.
Solution: Tinning/reflow the connector pads and inspecting traces shown on the diagram.
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☁ Practical repair checklist:
1. Try a different charger & cable.
2. Clean the port with isopropyl alcohol; inspect the pins.
3. Measure VBUS; verify continuity across the input fuse.
4. Check BAT voltage at battery pads and PMIC BAT pin.
5. Measure thermistor (NTC) values to ensure temperature sensing is correct.
7. If PMIC suspected: compare PMIC input/BAT pins to expected voltages; replace with known good PMIC if confirmed.
8. Replace the battery if the cell fails voltage/holding charge tests.