Single-cell Li-Ion linear charger in a small 8-pin package
The Texas Instruments BQ2057CTSTRG4 is a linear charge-management IC designed for single-cell Lithium Ion or Lithium Polymer battery packs. It targets the charge voltage at 4.2V, the standard termination for one Li-Ion cell, and uses a constant-current / constant-voltage (CC/CV) profile. The charge current is programmable via an external resistor — no I2C or firmware needed, just a resistor value to set the current limit.
The 4.2V battery pack voltage is fixed internally — this part is for single-cell Li-Ion packs only, not for 4.1V or 4.35V chemistries. The programmable charge current (set by a resistor from PROG to GND) lets you match the charge rate to the cell capacity: a 500 mAh cell might charge at 0.5C (250 mA), a 2000 mAh cell at 1C (2 A), but the linear regulator dissipates the voltage drop as heat, so the actual current is limited by thermal management in the 8-TSSOP package. Operating temperature spans -20°C to 70°C, which covers most portable consumer and industrial gear — handheld scanners, medical monitors, IoT sensors — but not automotive under-hood or engine-bay environments. The 15V absolute maximum supply input gives headroom for common 5V or 12V wall adapters.
Active lifecycle — no end-of-life watch needed
No last-time-buy clock is ticking, and no official successor part has been issued.
Surface-mount 8-TSSOP — what to expect on the board
The 8-TSSOP package (0.173" body width, 4.40 mm) is a common small-outline footprint for linear chargers. It is surface-mount only, so rework requires hot air or a reflow oven — not a field-swap part for a technician's kit.