TP4056 PCB Design Guide: Footprint, Pinout, and Alternatives
1 A single-cell Li-ion linear charger on ubiquitous red and blue modules
The TP4056 is the chip on the red and blue Li-ion charger modules that cost less than a coffee. It is a linear single-cell charger in an ESOP-8 with an exposed thermal pad: constant-current then constant-voltage charging to a fixed 4.2 V ±1%, charge current programmable up to 1000 mA with a single resistor, C/10 termination, and two status outputs for LEDs. The manufacturer is NanJing Top Power ASIC Corp., and the current datasheet (REV 2.3, in Chinese) lives on their toppwr.com site.
Note that widely circulated module lore lags the datasheet. The current-programming formula in REV 2.3 is RPROG = 1100 / IBAT, so the famous 1.2 kΩ resistor on most modules programs about 900 mA, not the 1 A the old app notes promised — 1 A takes 1.1 kΩ. Small difference, but it matters when you are sizing a supply or debugging charge times.
The chip itself is nearly foolproof; the ways people deploy it are not. Powering a load during charge without a load-sharing circuit, TEMP pins disabled at the factory, missing thermal copper, and the absence of any battery-protection functions account for most TP4056 field problems. All five are covered below.
What breaks boards
Never power a load straight off the battery while charging
If a system load hangs directly on the BAT pin during charge, the charger cannot tell load current from charge current: termination is based on the charge current falling to C/10, so the load can hold the current above the threshold forever, or the cell can micro-cycle between recharge and done. The fix is a load-sharing circuit — a P-MOSFET and Schottky diode that route the load to the input supply while it is present and to the battery only when it is not. Chargers with integrated power-path (BQ24074) solve this properly.
Cheap modules ship with the TEMP pin disabled
The datasheet is explicit that connecting the TEMP pin to GND disables battery temperature detection — and that is exactly how most bare modules ship, with the pin strapped low through a resistor. There is then no NTC protection at all: the cell will happily charge frozen or hot. For anything safety-critical or enclosed, wire the pin to a real 10 kΩ NTC thermistor mounted against the cell.
RPROG sets the current — and 1.2 kΩ is 900 mA, not 1 A
Charge current follows RPROG = 1100 / IBAT: the datasheet table runs 30 kΩ → 50 mA, 10 kΩ → 130 mA, 5 kΩ → 250 mA, 2 kΩ → 580 mA, 1.2 kΩ → 900 mA, 1.1 kΩ → 1000 mA. The "1.2 kΩ gives 1 A" figure comes from older datasheet revisions and module folklore; per the current REV 2.3 sheet, a full 1 A needs 1.1 kΩ. Also size the current for the cell: 1 A into a small 400 mAh pouch is a 2.5C abuse.
It is a linear charger — the exposed pad is not optional
The die dissipates (VIN − VBAT) × IBAT: charging a low cell at 3 V from 5 V at 1 A is about 2 W in an 8-pin package. The datasheet requires the bottom heat-sink pad to be soldered to the board with vias in the pad area and a generous copper pour. Skimp on that and nothing dramatic happens — thermal regulation quietly folds the charge current back when the junction reaches its 145 °C limit, and charging just takes mysteriously long. If your "1 A" module charges at 500 mA, check the copper first.
No protection functions, and 4.2 V only
The TP4056 is a charger, not a battery-management system: it has no over-discharge cutoff, no short-circuit protection for the cell, and no over-current limit on discharge. Pair it with a DW01A protector and FS8205A dual MOSFET (the combination on the better modules) or use a protected cell. And the 4.2 V float voltage is fixed — never use it on LiFePO4 (3.65 V chemistry) or on 2S packs, which it can neither balance nor terminate correctly.
Key specifications
| Parameter | Value | Source |
|---|---|---|
| Input range | VCC 4.0 V min / 5 V typ / 8.0 V max (operating); absolute max VCC 8 V | TP4056 REV_2.3 electrical characteristics table (VCC row) and absolute maximum ratings |
| Charge voltage | 4.2 V ±1% (VFLOAT 4.158 / 4.2 / 4.242 V, 0 °C ≤ TA ≤ 85 °C) | TP4056 REV_2.3 electrical characteristics table, VFLOAT row; features list '4.2 V preset charge voltage, ±1% accuracy' |
| Max charge current | 1000 mA programmable (IBAT 850 / 1000 / 1150 mA at RPROG = 1.1 kΩ; BAT pin absolute max 1200 mA) | TP4056 REV_2.3 features ('up to 1000 mA programmable charge current') and IBAT row of electrical characteristics table |
| RPROG to current formula | RPROG (kΩ) = 1100 / IBAT (mA); datasheet table: 30 kΩ → 50 mA, 10 kΩ → 130 mA, 5 kΩ → 250 mA, 2 kΩ → 580 mA, 1.2 kΩ → 900 mA, 1.1 kΩ → 1000 mA | TP4056 REV_2.3 'Setting the charge current' section (formula RPROG = 1100/IBAT) and RPROG/IBAT table |
| Termination threshold (C/10) | Charge terminates when IBAT falls to 1/10 of the programmed value after VFLOAT is reached (VPROG < 100 mV for > tTERM, 1.8 ms typ); ITERM 120/130/140 mA at RPROG = 1.1 kΩ | TP4056 REV_2.3 'Charge termination' section and ITERM / tTERM rows of electrical characteristics table |
| Package thermal pad requirement | Bottom heat-sink pad must be soldered well to the PCB with vias in the pad area and large copper pour (multilayer PCB with ample vias recommended); poor heat-sinking causes thermal regulation (TLIM 145 °C junction) to silently reduce charge current | TP4056 REV_2.3 application notes item 1 (ESOP8/EMSOP8 pad soldering/via guidance) and TLIM row of electrical characteristics table |
Verified against the manufacturer datasheet on 2026-07-09. Confirm the current revision before production use.
Alternatives
- MCP73831 — 500 mA in SOT-23-5 with an English Microchip datasheet — cleaner for small cells where 1 A is too much anyway.
- BQ24074 — TI charger with integrated power-path: load-while-charging done right, no external MOSFET circuit needed.
- TP5100 — the same family's switching charger: 2 A capability and 2S (8.4 V) support, at the cost of an inductor.
Common questions
- What resistor sets the TP4056 charge current?
- RPROG from the PROG pin to ground, with RPROG (kΩ) = 1100 / IBAT (mA) per the current REV 2.3 datasheet. So 1.1 kΩ programs 1 A, the 1.2 kΩ fitted to most modules programs about 900 mA, 2 kΩ gives 580 mA, and 10 kΩ gives 130 mA.
- Can I power my circuit while the TP4056 is charging the battery?
- Not directly from the BAT pin. Load current prevents correct C/10 termination and can micro-cycle the cell. Add a P-MOSFET load-sharing circuit so the load runs from the input supply during charge, or use a charger with built-in power-path such as the BQ24074.
- What does the TP4056 TEMP pin do, and can I tie it to GND?
- TEMP monitors a battery NTC thermistor and suspends charging outside the safe temperature window. The datasheet confirms that connecting TEMP to GND disables temperature detection — which is how most cheap modules ship. Tie it to a 10 kΩ NTC against the cell for anything safety-critical.
- Does the TP4056 include battery protection?
- No. It charges to 4.2 V ±1% and stops; there is no over-discharge, short-circuit, or discharge over-current protection. Use the module variant with the DW01A + FS8205A protection pair, or a protected cell — and never use a TP4056 on LiFePO4 or 2S packs, since the 4.2 V termination is fixed.