Schematic Design Review

Does this have backflow protection
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
R1
Resistance
470 Ω
STAT2
Part Type
LED
R3
Resistance
470 Ω
C1
Capacitance
4.7uF
IC2
Manufacturer Name
Microchip Technology
Manufacturer Part Number
MCP73871-1AAI/ML
PG
5V
R2
Resistance
470 Ω
STAT1
VBAT


MCP73871-1AAI/ML - SUBLAYOUT

MCP73871-1AAI/ML - SUBLAYOUT thumbnail
Lipo battery charger with 3v3 @ 1.8A output.

Properties

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MCP73871-1AAI

Pricing & Availability

Distributor

Qty 1

Digi-Key

$2.46–$2.56

LCSC

$2.02

Mouser

$2.71

Controls