Schematic Design Review

charlie-allmon

Does this have backflow protection

Thought for 2 mins 7 sec

flux

Short answer: Yes — the charger IC here, IC2 (MCP73871), integrates reverse/backflow protection.

What the datasheet says (verbatim figures)

Reverse‑blocking protection on input: “provides protection from a faulted or shorted input,” preventing the battery from discharging into the input through internal body diodes (Section 6.1.1.4 Reverse‑Blocking Protection).
Reverse discharge limits:
- UVLO: “battery reverse discharge current is less than 2 μA.”
- Electrical characteristics (Output reverse leakage current, IDISCHARGE): 30–40 μA in Shutdown (various conditions); −6 to −13 μA at Charge Complete.
Power‑path with ideal‑diode operation: Low‑loss power‑path management; when input current is insufficient, the ideal‑diode allows the battery to supplement the system load (this is intended behavior, not a backflow fault).

Schematic note

The anodes of STAT1, STAT2, and PG LEDs are tied to the input net (“Net (CIN - P2)”), so the PG/STAT outputs are not pulled above VIN. The datasheet cautions that PG “must not be pulled up higher than VIN” due to an internal diode path back to VIN; your wiring is consistent with that.

Clarify backflow direction

Check external diode need

Verify leakage expectations

Review my PG pullup

Consider dual-source behavior

Resistance

470 Ω

VBAT

STAT2

Part Type

LED

Resistance

470 Ω

Capacitance

4.7uF

IC2

Manufacturer Name

Microchip Technology

Manufacturer Part Number

MCP73871-1AAI/ML

Resistance

470 Ω

STAT1

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