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| TP4056 battery charger circuit diagram showing USB input, charging IC, protection circuit, MOSFET, battery connections and key components. |
TP4056 Battery Charger Module Circuit Diagram, Pinout, Wiring and Repair Guide
The TP4056 battery charging module is one of the most widely used low-cost solutions for charging a single-cell 3.7V nominal lithium-ion battery. The TP4056 itself is a linear constant-current/constant-voltage (CC/CV) charger IC designed for a single Li-ion cell, with a fixed final charge voltage of approximately 4.2V and a programmable charging current of up to about 1A.
A common protected TP4056 module combines the charger IC with a DW01A battery protection IC and an FS8205A dual MOSFET. This creates two different functions on the same PCB: the TP4056 manages battery charging, while the DW01A and MOSFET section provides battery protection against conditions such as overcharge, over-discharge, overcurrent and short circuit. Not every TP4056 board includes this protection section, so the actual PCB must be checked before assuming that protection is present.
This guide explains the TP4056 circuit diagram, pinout, wiring, charging current setting, DW01A protection circuit, practical testing methods and common repair faults in a way that is useful for electronics troubleshooting rather than simply reproducing a module schematic.
TP4056 Charger Module Specifications
| Parameter | Specification |
|---|---|
| Charger IC | TP4056 |
| Charger Type | Linear Li-ion Battery Charger |
| Battery Configuration | Single-cell Li-ion/LiPo |
| Nominal Battery Voltage | 3.7V |
| Charge Voltage | 4.2V |
| Maximum Programmable Charge Current | Approximately 1A |
| Typical Input Supply | 5V USB |
| Charging Method | Constant Current / Constant Voltage |
| Package | SOP-8 / ESOP-8 variants |
| Temperature Monitoring | TEMP/NTC input |
| Status Outputs | CHRG and STDBY |
| Automatic Recharge | Supported |
| Trickle-Charge Threshold | Approximately 2.9V |
| Thermal Regulation | Integrated |
Different TP4056 silicon versions and manufacturers can have slightly different electrical specifications and package options. The device datasheet should therefore be treated as the final reference when repairing an individual board.
TP4056 Pinout and Pin Functions
The standard TP4056 uses an 8-pin arrangement. Correctly identifying these pins is the first step when diagnosing a dead charging module.
| Pin | Name | Function |
|---|---|---|
| 1 | TEMP | Battery temperature sensing input |
| 2 | PROG | Charge-current programming and monitoring |
| 3 | GND | Ground |
| 4 | VCC | Positive input supply |
| 5 | BAT | Battery positive connection |
| 6 | STDBY | Charge-complete status output |
| 7 | CHRG | Charging-status output |
| 8 | CE | Chip-enable input |
The TEMP pin can be connected to an NTC thermistor in the battery pack. The datasheet describes a temperature-sense window in which charging is suspended when the TEMP voltage falls outside the specified limits. The temperature function can also be disabled by grounding TEMP, although that removes the external temperature-monitoring function.
The CE pin is an enable input, not a passive connection that must always be considered internally tied to VCC. A high CE level enables normal operation, while pulling CE low places the charger into shutdown.
TP4056 Circuit Diagram Explained
A typical protected TP4056 module can be divided into three sections:
USB 5V input → TP4056 charger → battery connection
and, on protected versions:
Battery → DW01A protection IC → FS8205A MOSFET → OUT terminals
This separation is important during repair. A board may still contain a healthy TP4056 charger while the protection MOSFET section is damaged, or the opposite can happen.
USB Input Section
The input is commonly provided through a Micro-USB connector, although newer boards may use USB-C.
The normal USB input path supplies approximately 5V to the charger. The connector's positive supply reaches the TP4056 VCC pin, while ground connects to the circuit ground. The actual charging module should be designed around the input range specified for the particular TP4056 variant; standard TP4056 applications commonly use a 5V source.
A small input capacitor is used to reduce high-frequency noise and help stabilise the supply. In a practical repair, measure the voltage directly at VCC-to-GND on the TP4056 rather than assuming that the voltage present at the USB connector is reaching the IC.
Input Capacitor C3
A capacitor such as 100 nF may be used across the input supply for high-frequency decoupling, while other reference designs use additional bulk capacitance.
Its role is not to increase charging current. It mainly helps reduce supply noise and transient disturbances around the charger IC.
When troubleshooting, inspect the capacitor for cracking or leakage, especially on boards that have been mechanically stressed or exposed to heat.
TP4056 PROG Pin and Charging Current
The PROG pin controls the programmed charging current through an external resistor connected to ground.
A common protected module uses a 1.2 kΩ resistor, and the TP4056 electrical characteristics show approximately 1A charging current at that resistance under the specified conditions. Therefore, the original script value of approximately 833 mA for 1.2 kΩ should not be used as a general TP4056 value.
A practical relationship for the common TP4056 implementation is approximately:
IBAT = 1200 / RPROG
where RPROG is in ohms, and the result is in amperes under the corresponding datasheet conditions.
For example:
RPROG = 1.2 kΩ → approximately 1A
RPROG = 2.4 kΩ → approximately 0.5A
The exact resistor-selection table in the datasheet should be used when changing the charge current.
Practical Tip for Charge-Current Repair
Do not select a smaller PROG resistor simply to obtain faster charging. The battery capacity, cell specification, PCB thermal performance and USB power source must all be suitable for the intended current.
A small charging board that becomes excessively hot while charging at its programmed current may have inadequate thermal dissipation, excessive input-to-battery voltage drop or a damaged component.
BAT Pin and Battery Connection
The BAT pin is the positive charging and battery-sense connection of the TP4056.
On a basic charger board, the battery positive terminal connects directly to BAT and the battery negative terminal connects to GND. On a protected board, the battery and output path are routed through the protection section.
The TP4056 regulates the battery to approximately 4.2V for the standard Li-ion charging configuration.
One important distinction is that BAT+ and OUT+ are not always separate electrically, while the negative side on protection-enabled modules is often switched through the DW01A and MOSFET section. Therefore, always trace the PCB before assuming that B-, OUT-, and GND are identical nodes.
CHRG and STDBY Status LEDs
The TP4056 provides two open-drain status outputs.
CHRG is pulled low while the battery is actively charging.
STDBY is pulled low when the charge cycle is terminated, and the charger enters standby.
Reference circuits commonly connect these outputs to red and green LEDs through current-limiting resistors.
A status LED is useful for diagnosis, but it should not be treated as proof that the battery is receiving the correct charging current. Always confirm the actual battery voltage and charging current with test equipment.
TEMP Pin and Battery Temperature Monitoring
The TEMP pin monitors battery temperature when used with an appropriate NTC thermistor.
The datasheet specifies that charging is suspended when the TEMP voltage falls below approximately 45% or rises above approximately 80% of the supply voltage for the specified duration.
When a module has temperature sensing enabled, and the NTC is disconnected or incorrect, the charger may refuse to charge even though VCC, BAT and the other components appear normal.
This is a useful diagnostic clue when a replacement battery or custom battery pack has been installed.
DW01A Battery Protection Circuit
A protected TP4056 module often includes a DW01A protection IC.
The DW01A does not perform the same job as the TP4056. Its main purpose is battery protection. It monitors the cell voltage and current-related conditions and controls the MOSFET path accordingly.
Typical protection functions include:
Overcharge protection
Over-discharge protection
Overcurrent protection
Short-circuit protection
The DW01A works together with a dual MOSFET such as the FS8205A to disconnect the battery when a protection condition is detected.
FS8205A Dual MOSFET Operation
The FS8205A is a dual N-channel MOSFET commonly used with the DW01A.
The protection IC controls the MOSFET gates so that the battery can be disconnected from the load when an unsafe condition is detected. This is why the MOSFET section should be checked separately from the TP4056 charger section during troubleshooting.
A shorted MOSFET can cause unusual battery behaviour, while an open or poorly soldered MOSFET can interrupt the output path.
Capacitors C1 and C2
The battery-side capacitors help stabilise the power rails and suppress noise.
A module may use values such as 10 µF around the battery and charger nodes, although exact component values vary between boards.
When a TP4056 module has unexplained heating or refuses to charge, checking the BAT-to-GND line for a shorted ceramic capacitor is often worthwhile before replacing the charger IC.
TP4056 Charging Process
Stage 1: Trickle Charging
When the battery voltage is below the TP4056's trickle-charge threshold, the charger starts with a lower current.
The documented threshold is approximately 2.9V, with the trickle current being much lower than the normal programmed charge current.
This prevents a deeply discharged cell from immediately receiving the full programmed charging current.
Stage 2: Constant-Current Charging
After the battery reaches the required threshold, the TP4056 supplies the programmed constant current.
For a typical 1A configuration, the charging current remains near the programmed level while battery voltage continues rising toward the final regulation point.
Stage 3: Constant-Voltage Charging
As the battery approaches 4.2V, the TP4056 changes from constant-current operation to constant-voltage regulation.
Charging current gradually falls during this phase. The charge cycle terminates when the current falls to the TP4056's specified termination level, commonly referred to as C/10 termination.
TP4056 Wiring Guide
For a basic unprotected board, the wiring is straightforward:
USB 5V positive → TP4056 VCC
USB GND → TP4056 GND
Battery positive → TP4056 BAT
Battery negative → TP4056 GND
For a protected module, connect the battery to the B+ / B- terminals and the external load to OUT+ / OUT-, provided those labels are actually present on that particular PCB.
Do not assume every TP4056 module uses identical terminal markings. Some inexpensive boards omit the protection section entirely.
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| TP4056 IC pinout with TEMP, PROG, GND, VCC, BAT, STDBY, CHRG and CE pins for battery charger circuit testing and repair. |
Problem: TP4056 Module Does Not Charge
Check the USB input.
Measure the voltage at VCC and GND.
A nominal 5V USB supply should be present on a typical TP4056 application. If there is no voltage at VCC, inspect the connector, solder joints, PCB trace and any protection component between the USB connector and the IC.
Check BAT voltage.
Measure the battery voltage directly.
If the battery is extremely low, the TP4056 may remain in trickle-charge mode initially. If the battery voltage is abnormal, unstable, or immediately collapses under charging, investigate the battery itself before condemning the module.
Check the PROG resistor.
With power removed, measure the PROG resistor.
A changed, cracked, or incorrectly replaced resistor can produce the wrong charging current. Compare the measured value with the intended design.
Check the TEMP circuit.
If the TEMP function is enabled, inspect the NTC connection.
A disconnected NTC or an incorrect resistance value can cause charging to remain disabled because the charger interprets the temperature-sense voltage as being outside its allowed range.
Problem: Charging LED Is ON, but Battery Voltage Does Not Rise
Check the BAT line.
Measure the voltage directly between BAT and GND while the battery is connected.
Then measure the battery itself.
A significant difference can indicate a damaged track, connector, solder joint or protection-path issue.
Check for a Shorted Battery-Side Capacitor
Disconnect power and inspect the BAT rail for a low-resistance short.
A failed capacitor can pull down the charger output and cause the TP4056 to heat without successfully charging the cell.
Check the Protection MOSFET
On protected modules, inspect the FS8205A and DW01A area.
A damaged MOSFET can interrupt the battery/output path even when the TP4056 is functioning correctly.
Problem: TP4056 IC Becomes Very Hot
The TP4056 is a linear charger, so the voltage difference between the USB input and battery voltage is dissipated as heat inside the IC.
For example, charging a battery around 3.7V from a 5V source at a high current creates significant power dissipation compared with a switching charger.
Check the Charge Current
Verify the PROG resistor and actual charging current.
A board configured for approximately 1A should not be modified for higher current simply by changing the resistor unless the IC variant, thermal design and battery are suitable.
Check for Excessive Input Voltage
Do not treat the TP4056 as a high-voltage charger. The standard device is designed for low-voltage input operation, and the exact absolute maximum rating depends on the particular version. Published TP4056 documentation lists an absolute maximum VCC of about 8V, not 9V or 12V.
A regulated 5V source is the normal practical choice.
Problem: Green LED or STDBY LED Does Not Work
Check the LED, resistor, solder joints and STDBY connection.
Because CHRG and STDBY are open-drain outputs, the LED circuit depends on the correct pull-up arrangement. An LED being off does not always mean that the charger has failed.
Use the battery voltage and charging current as primary diagnostic measurements.
Problem: TP4056 Works but OUT Terminals Have No Output
This problem is common on protection-enabled modules.
First identify whether the board actually contains DW01A + FS8205A.
Then check:
Battery voltage at B+ and B-.
Protection IC supply.
MOSFET solder joints.
OUT+ and OUT- continuity.
Signs of over-discharge or short-circuit protection activation.
A protected module may intentionally disconnect its output under a fault condition. Some boards can still accept charging through the protection arrangement even when discharge is disabled, depending on the specific protection circuit.
Practical TP4056 Circuit Repair Method
A reliable repair usually starts at the power input and moves toward the battery instead of replacing the IC immediately.
Step 1: Inspect the PCB
Look for burnt parts, cracked resistors, damaged USB connectors, lifted pads and solder bridges.
Step 2: Check VCC
Confirm that the TP4056 receives the expected input supply.
Step 3: Check BAT
Measure the battery voltage and inspect the BAT track.
Step 4: Check PROG
Verify the charge-current programming resistor.
Step 5: Check TEMP
Confirm that the temperature-sense circuit is correctly connected.
Step 6: Check Protection Components
On protected boards, test the DW01A and FS8205A section separately.
Step 7: Confirm Actual Charging Current
Do not rely only on the LED. Measure current using an appropriate meter or controlled test setup.
This approach helps distinguish an input fault, charger fault, battery fault and protection-circuit fault before unnecessary component replacement.
Important TP4056 Design Tips
A TP4056 module is simple, but several design choices strongly affect reliability.
The charger should be used with a single Li-ion/LiPo cell designed for a 4.2V charging voltage. A LiFePO4 cell must not be charged with a normal 4.2V TP4056 configuration.
The battery should also be capable of accepting the programmed charging current. A small cell should not automatically be charged at 1A simply because the module is configured for 1A.
For custom designs, keep the charger and battery connections short, use suitable copper width and ensure adequate thermal conduction around the TP4056 package.
TP4056 Applications
The TP4056 is commonly used in:
Single-cell Li-ion battery chargers
DIY electronics projects
Small portable devices
Rechargeable sensor systems
Wearable electronics
Bluetooth accessories
Battery-powered controllers
Small power-bank style projects
USB rechargeable prototypes
The device is especially attractive when a simple USB-powered single-cell charger is required, and the thermal limitations of a linear charger are acceptable.
Official TP4056 Datasheet Reference
For exact electrical limits, pin functions, charge-current programming and package information, use the manufacturer's datasheet for the specific TP4056 device.
TP4056 Datasheet: DigiKey-hosted manufacturer datasheet
UMW TP4056 Datasheet: UMW Semiconductor technical documentation
Note Point: Always verify the exact TP4056 module circuit, battery chemistry, protection section and datasheet before repairing or modifying a lithium-battery charging board.
Disclaimer: This article is for educational and electronics-repair reference; lithium batteries can be hazardous, so use suitable tools, correct components and safe battery-handling procedures.
