Part of the Day · MCP1700-3302E — SOT-23 3.3V 250mA ultra-low-power LDO regulator (marking CS)

Part of the Day · 2026-11-04

A small CMOS LDO widely used to make 3.3V in devices that stay on for a long time from batteries. Its quiescent current when idle is a very low 1.6µA typical, and it delivers up to 250mA. With only three leads, it has no enable pin. On the SOT-23 version, the first two characters on the chip, CS, indicate 3.3V.

Actual size

↓ Actual size, left edge aligned to 0 on the ruler

One ruler tick = 1mm. On PC this is actual size on a 24-inch FHD monitor at 100% zoom; on iPhone it adjusts automatically. For other screens, use “Calibrate ruler” below.

Enlarged (SOT-23 · top view · approx. 20×)

Pins 1 GND · 2 VOUT (output) · 3 VIN (input) — the side with a single lead is the input

Package SOT-23 · Marking CS

Key specifications

Values are from the Microchip Technology datasheet.

Marking and pins

Marking code CS · Pins 1 GND · 2 VOUT (output) · 3 VIN (input) — the side with a single lead is the input

Typical uses

• 3.3V supply for devices running a long time on 2~3 alkaline cells or one Li-ion cell — only 1.6µA while idle
• Always-on battery devices such as smoke detectors, CO2 detectors and alarms (datasheet application examples)
• Microcontroller power and low-power voltage reference

Companion & similar parts

• MCP1700T-3302E/TT — Order code — T = tape and reel, 330 = 3.3V, 2 = 2% tolerance (standard), E = -40~125℃, /TT = SOT-23
• MCP1700T-1802E/TT · -2502E · -2802E · -5002E — Same series, other output voltages 1.8V · 2.5V · 2.8V · 5.0V — chip markings CM · CP · CQ · CU
• MCP1700-3302E/TO — TO-92 version of the same chip — different pin order (1 GND · 2 VIN · 3 VOUT)
• MCP1700T-3302E/MB — SOT-89 version of the same chip — 104℃/W thermal resistance, handles heat better (1 GND · 2 VIN · 3 VOUT)

The SOT-23 version carries four characters: the first two give the voltage (CS = 3.3V) and the rest is a traceability code (datasheet page 17). Only the 2.9V version starts with GC instead of C. Even for the same chip, the VIN and VOUT pin positions are swapped between SOT-23 and SOT-89/TO-92, so always check the pin table when changing packages. If the output is shorted or too much current is drawn, it repeatedly shuts off briefly and restarts. SOT-23 has a thermal resistance of 212℃/W, so at 40℃ ambient it can only dissipate about 401mW — running 250mA continuously from a 5V input to a 3.3V output (about 0.43W) exceeds that.