Overview

The ME2108 (ME2108A33) is an ultra-low power Pulse-Frequency Modulation (PFM) step-up (boost) DC-DC converter IC manufactured by Nanjing Micro One Electronics (MicroOne). Housed in a tiny 3-pin SOT-23-3, SOT-89-3, or TO-92 package, it steps up single-cell or dual-cell battery voltages (0.9V…3.0V0.9\text{V} \dots 3.0\text{V} AA/AAA/NiMH batteries) to a fixed 3.3V DC output voltage rail.

Drawing an ultra-low quiescent current of just 5.5 μA5.5\ \mu\text{A}, the ME2108 is widely used in low-power microcontroller battery boards, wireless sensor nodes, electronic toys, and handheld meters.

Quick reference

Input Voltage Range (VIN)0.9 V to 5.0 V DC (Startup voltage 0.9 V0.9\text{ V})
Output Voltage (VOUT)Fixed 3.3 V DC (ME2108A33) / Fixed 5.0V (ME2108A50) (±2%\pm 2\% accuracy)
Quiescent Current (IQ)5.5 μA5.5\ \mu\text{A} typical standby drain
Switching ControlPFM (Pulse-Frequency Modulation, up to 180 kHz180\text{ kHz})
Internal SwitchIntegrated N-channel power MOSFET (up to 400 mA400\text{ mA} switch current)
EfficiencyUp to 85%85\% typical
PackageSOT-23-3 / SOT-89-3 / TO-92

Pinout (SOT-23-3 Package)

text
             ┌───┴───┐
       VSS  1│ 1   3 │ LX (Inductor Switch Node)
       OUT  2│       │
             └───────┘
PinNameTypeDescription
1VSSPowerGround Reference (0 V)
2OUTPower / SenseFixed Voltage Output (3.3V DC) & Internal Feedback Sense Pin
3LXOutputInternal N-MOSFET Drain Switch Node (Connect to Inductor & Schottky Diode)

Standard Single-Cell Battery Boost Circuit

text
  Single AA Battery (+1.5V DC) ───[ Inductor 22µH to 47µH ]───┬─── [Pin 3: LX]
                                                               │
                                                       [Schottky Diode 1N5819]
                                                               │
  Regulated Output (+3.3V DC) ◄────────────────────────────────┼─── [Pin 2: OUT]
                                                               │
                                                      [10µF Capacitor to VSS]

Common mistakes

  • Attempting to draw high currents (>150mA> 150\text{mA}) from a 0.9V input: Single 1.5V AA batteries can supply up to 100 mA…150 mA100\text{ mA} \dots 150\text{ mA} at 3.3V. Attempting to draw higher currents collapses the input battery voltage below the 0.9V0.9\text{V} cutoff.
  • Using slow silicon diodes instead of Schottky: The PFM switching frequency (180 kHz180\text{ kHz}) requires a low-forward-voltage Schottky diode (such as 1N5819 or SS14).

Notes

  • ME2108 vs HT7733: ME2108A33 and HT7733A are pin-compatible 3.3V PFM boost regulators designed for single-cell battery applications.

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