Key Specs
| Spec | Value | Condition | Source |
|---|---|---|---|
| Battery Chemistry | Lithium Ion | Digi-Key | |
| Battery Pack Voltage | 4.2V | Digi-Key | |
| Charge Current (Max) | 340mA | Digi-Key | |
| Current Charging | - | Digi-Key | |
| Fault Protection | - | Digi-Key | |
| Interface | USB | Digi-Key | |
| Mounting Type | Surface Mount | Digi-Key | |
| Number Of Cells | 1 | Digi-Key | |
| Operating Temperature Range | -40°C ~ 85°C (TA) | Digi-Key | |
| Package Case | SOT-23-5 Thin, TSOT-23-5 | Digi-Key | |
| Programmable Features | - | Digi-Key | |
| Supplier Device Package | TSOT-23-5 | Digi-Key | |
| Voltage Supply (Max) | 7V | Digi-Key |
When To Use
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USB-powered 1-cell Li-ion charger @ 340mA: The 7V maximum supply voltage and 340mA charge current max match USB 5V input rails and single-cell Li-ion packs perfectly. A generic linear regulator would waste power and risk thermal shutdown; a synchronous buck controller would complicate the design unnecessarily for this low current and single-cell chemistry.
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Compact portable device with SOT-23-5 mounting: The TSOT-23-5 package fits tight board space and low profile requirements, with an operating range down to -40°C for rugged environments. Larger packages or multi-cell chargers either wouldn’t fit or lack the thermal margin, risking overheating or mechanical incompatibility.
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Single-cell Li-ion charger with fixed USB input: The device’s built-in USB interface and 4.2V battery voltage support ensure straightforward integration without external communication or complex programming. Using a programmable charger or multi-phase buck controller here might cause unnecessary complexity and increased BOM cost without benefit.
When Not To Use
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Charging multi-cell Li-ion battery packs: The max battery voltage of 4.2V limits this device to single-cell applications only. Use a multi-phase buck controller designed to balance and charge multiple cells safely.
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High-current fast charging >340mA: The 340mA charge current max is insufficient for higher power needs. Use a high-current synchronous buck with external FETs to handle larger currents efficiently and avoid thermal failure.
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Battery-operated IoT devices with ultra-low standby current: The quiescent current is not optimized for μA-level sleep modes. Use a low-IQ PFM buck to maximize battery life during long standby periods.
Application Notes
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the BAT pin is noise-sensitive; keep battery connection wiring short and low-impedance to prevent voltage spikes during switching transitions.
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The switching node (SW) is internal but closely coupled to the package’s exposed pad; ensure solid ground plane under the IC for thermal dissipation and minimize loop area to reduce EMI.
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USB input pin (VCC) requires stable 5V supply with appropriate bulk and ceramic capacitors placed close to the device to handle transient current demands.
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No external programming pins exist; charge current and voltage are fixed internally—external component selection is limited to input and battery filtering.
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Guard routing or ground stitching is recommended around SW and BAT pins to prevent coupling noise into the battery line and ensure stable charge termination.
Gotchas
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[Assuming stable battery voltage during startup]: Many designs assume the battery voltage will be near 4.2V at power-up. If the battery is deeply discharged (<1V), the charger may enter an undefined state or fail to begin charging properly, showing no current draw on scope.
Fix: Verify battery voltage before enabling charger or include a pre-charge circuit to raise cell voltage into valid range. -
[Neglecting input capacitor ESR and placement]: Using a high-ESR input capacitor or placing it far from VCC pin causes voltage dips during switching, triggering erratic charge current pulsing or oscillation visible on the SW node.
Fix: Use low-ESR ceramic capacitors placed within 5mm of the device’s VCC pin with wide, short traces. -
[Output capacitor ESR too high or missing]: The device relies on the battery as stable output; however, if the battery is disconnected or replaced with a large capacitor with high ESR, the charger can become unstable, causing output ripple and charge current oscillations.
Fix: Always connect a proper Li-ion battery or low-ESR capacitor at BAT pin and avoid large electrolytics alone. -
[Inadequate thermal relief on PCB copper pour]: The TSOT-23-5 package dissipates heat through the PCB; insufficient copper under the device leads to thermal runaway during continuous charge, with junction temperature rising unnoticed on ambient measurement.
Fix: Use thermal vias and at least 1in² of 2oz copper pour under the device connected to ground plane for effective heat spreading.