TP4056 - 1A Single-Cell Li-Ion / LiPo Linear Charge Management IC

What Is the TP4056 and How Does It Work?

Charging a lithium cell safely means following a specific profile, and the TP4056 does it automatically:

1. Trickle charge - if the cell is below about 2.9V (deeply discharged), it charges gently at 1/10 the set current to avoid stressing a weak cell.
2. Constant current (CC) - once above 2.9V, it pushes the full programmed current (say 1A) into the cell while the voltage climbs.
3. Constant voltage (CV) - when the cell reaches 4.2V, it holds that voltage and lets current taper.
4. Termination - when current tapers to 1/10 of the set value, charging stops. It auto-recharges if the cell later drops below ~4.05V.

You set the current with one resistor on the PROG pin. Roughly: 1.2kΩ gives ~1000mA, 2kΩ gives ~580mA, 5kΩ gives ~250mA. Lower current means less heat - remember that number, it comes back.

The chip has a built-in thermal regulation loop: if the die hits about 120°C it automatically reduces charge current to protect itself. That's a safety net, not a design target - if your TP4056 is relying on thermal regulation, you set the current too high.

Position among chargers: the TP4056 is the entry-level 1A linear single-cell charger. Need 2A or better efficiency? That's a switching charger like the TP5000. Need a tiny 500mA charger in SOT-23? That's the MCP73831. Need charging plus load-sharing and power-path? That's an IP5306-class part.

What Are the Specifications of the TP4056?

Pinout (SOP-8)

The Numbers That Bite

• Heat = (Vin − Vbat) × Icharge: this is a linear charger, so it burns the input-to-battery voltage difference as heat inside that little SOP-8. Charge a 3.7V cell at 1A from 5V USB and that's (5.0 − 3.7) × 1.0 = 1.3W in an 8-pin package. That's a lot. The single most effective fix is to lower the charge current - drop to 500mA and you halve the heat. Many cheap boards ship set to the full 1A, which is why "TP4056 overheating" is the top forum complaint.
• The exposed pad is not optional: the SOP-8 has a thermal pad on its belly. If it isn't soldered down to a copper pour, the heat has nowhere to go, thermal regulation kicks in early, and the chip derates the charge current. A board that "charges slowly" often just has a poorly-soldered pad.
• TEMP pin grounded = no battery temperature protection: the TP4056 can monitor cell temperature through an NTC thermistor on pin 1. Most cheap boards tie pin 1 straight to GND, disabling it entirely. If you want real temperature safety, cut that trace and wire a 10kΩ NTC with a 10kΩ divider - a fix documented repeatedly on the Arduino forum and the iSpindel project.

What Is the TP4056 Used For?

DIY and Maker Battery Projects

The default charger for hobby lithium projects - Arduino/ESP32 gadgets, portable sensors, LED projects. Cheap, single-resistor setup, status LEDs built in.

18650 and LiPo Cell Charging

Charging bare 18650 cells or LiPo packs from USB. Critical caveat: pair it with protection (see the 3-chip note below) if the cell is unprotected.

Small Power Banks

Simple USB power banks use the TP4056 for the charge side. Note it doesn't do load-sharing on its own - you can't cleanly charge and power a load from the same board without a power-path fix, which is where the IP5306 wins.

IoT and Battery-Backed Devices

Battery-backed sensor nodes and remote loggers that top up from a small solar panel or USB. Keep the charge current low here - solar input is weak and low current means less heat.

TP4056 vs TP5000 vs MCP73831

Pick TP4056 when: you want the cheapest, simplest single-cell USB charger and your current stays at or below ~500mA. It's the universal hobby default and it's well-documented everywhere.

Pick TP5000 when: the TP4056 runs too hot, you need 2A, or you're charging LiFePO4. Being a switching charger it wastes far less energy as heat - the right upgrade when thermal is your problem.

Pick MCP73831 when: board space is tight. In SOT-23-5 it's tiny, tops out at 500mA, and suits small wearables and compact PCBs where a SOP-8 won't fit.

Why Buy TP4056 from ICMASS?

• Original Nanjing Top Power parts with traceability. There are documented bad batches of TP4056 that draw ~1A from the battery even with USB disconnected and overheat - a latching failure traced to specific lots. Genuine, traceable parts are how you avoid that.
• In stock, ships from Shenzhen, tape-and-reel or cut-tape.
• The switching upgrade (TP5000) and the compact option (MCP73831) are available on the same order if your thermal or space needs change.
• From our experience, most "faulty TP4056" returns are actually a design set to full 1A with an unsoldered thermal pad - we can help you get the current and layout right before production.

Frequently Asked Questions About the TP4056

Q1: Why does my TP4056 get so hot when charging?

A: Because it's a linear charger - it burns the input-to-battery voltage difference as heat. The heat is (Vin − Vbat) × Icharge, so charging a 3.7V cell at 1A from 5V dissipates about 1.3W in the small SOP-8. This is the number-one complaint on the Arduino forum. The fix: lower the charge current by increasing the PROG resistor (a 2kΩ resistor drops you to ~580mA), and make sure the chip's exposed thermal pad is soldered to a copper pour.

Q2: How do I reduce the charge current?

A: Change the PROG resistor (often labeled R3 on modules). Roughly: 1.2kΩ ≈ 1000mA, 2kΩ ≈ 580mA, 2.4kΩ ≈ 500mA, 5kΩ ≈ 250mA. Higher resistance means lower current means less heat. For most hobby projects, 500mA is a good balance of charge speed and temperature.

Q3: Does the TP4056 protect my battery from over-discharge?

A: No. This is the most important thing to know. The TP4056 only charges - it has no over-discharge, over-current, or short-circuit protection for the battery. For that you need the 3-chip board that adds a DW01 protection IC and an FS8205 dual MOSFET. If you're charging bare 18650 or LiPo cells, always use the protected (3-chip) version, or the cell can be over-discharged and damaged.

Q4: Can I charge a battery and power my circuit at the same time?

A: Not cleanly with a plain TP4056. It has no load-sharing / power-path circuitry, so powering a load directly off the battery pin while charging confuses the termination logic and can stress the cell. For simultaneous charge-and-run, use a charger with power-path like the IP5306, or add proper load-sharing circuitry.

Q5: Can I charge from a modern USB-C charger?

A: Often no, on older USB-C modules. Many early USB-C TP4056 boards lack the CC pin pull-down resistors that USB-C chargers require to negotiate power, so a modern USB-C PD charger won't turn on. Use a USB-A-to-USB-C cable, an older charger, or a board with the correct CC resistors.

Q6: My TP4056 overheats even when it's NOT charging. What's happening?

A: This is a rare but documented failure - the chip draws around 1A from the battery with USB disconnected. It's been linked to specific bad batches on StackExchange, and swapping to a genuine part from a different lot resolved it. If you see this, disconnect the battery immediately and replace the chip with a traceable part.

Q7: Is it safe to charge a deeply discharged or damaged cell?

A: Be very careful. A cell that's dropped below ~2.5V or has ever been short-circuited can cause the TP4056 to overheat badly while trying to recover it, with real fire risk. Forum consensus is to dispose of cells that have gone that low - they're permanently damaged. The TP4056's trickle mode helps with mildly flat cells, but it's not a rescue tool for abused ones.

Q8: What do the CHRG and STDBY pins / LEDs mean?

A: CHRG (usually the red LED) is on while charging. STDBY (usually blue or green) comes on when charging is complete. Both are open-drain outputs, which is why they can sink LED current directly. If both are off with a battery connected, the chip is likely disabled (CE low) or in a fault state.

Q9: Why is my module drawing more current than I set, or the current keeps rising?

A: Some modules have been reported drawing ~1.6A instead of a set 0.8A after warming up - usually a faulty module or a wrong PROG resistor value. Verify the actual PROG resistor on the board matches the current you expect. If the behavior persists on a good resistor value, the chip is suspect; consider a switching charger like the TP5000 instead.

Pricing & Availability

Contact ICMASS for current pricing. We stock original TP4056 plus the switching upgrade (TP5000) and the compact SOT-23 option (MCP73831) for the same battery-charging designs.