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Contents

README

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MS721

Hangzhou Ruimeng Tech · Interface - Specialized · SOP-16

MS721 from Hangzhou Ruimeng Tech, in a SOP-16. Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin Name Type Function
1 BUSL2 bidirectional M-Bus interface port 2, part of ±50V differential pair for modulated half-duplex UART communication in both receive (voltage modulation detection) and transmit (current modulation) modes.
2 VB power_in Rectified bus voltage input from internal bridge rectifier providing DC voltage to internal reference circuits with minimum 9.3V in receive mode.
3 STC passive Supply storage capacitor connection port for 3.3V internal regulator, operating voltage range 3.8V to 6.4V with external capacitor CSTC.
4 RIDD passive External current-setting resistor connection (13kΩ to 80kΩ) that determines supply charging current ISTC for storage capacitor.
5 PF output Power failure signal output; outputs high (VBAT-0.6V to VBAT) when VVST > VSTC+0.6V indicating power good, low when power fails to alert MCU.
6 SC passive Sampling capacitor connection port for dynamic reference level circuit with external capacitor CSC charged at 40× discharge rate ratio (ISCcharge/ISCdischarge = 40).
7 TXI output Inverted UART data output from receive comparator TC3 with voltage levels 0V to 1.5V (low) or VBAT-0.6V to VBAT (high).
8 TX output UART data output from receive comparator TC3 decoded from M-Bus voltage modulation with voltage levels 0V to 1.5V (low) or VBAT-0.6V to VBAT (high).
9 BAT power_in Battery or auxiliary supply voltage input for logic level adjustment, operating range 2.5V to 3.8V recommended or -0.3V to 5.5V absolute maximum.
10 VS power_in Power source selection output synchronized with VDD; outputs VSTC-0.4V when powered from bus or high-impedance (0.3MΩ to 1MΩ) when battery powered to control external switching transistor.
11 VDD power_out Regulated 3.3V power supply output from internal voltage regulator with output voltage 3.1V to 3.4V at 1mA load and 5Ω output impedance.
12 RX input UART data input from microcontroller for slave-to-master transmission, accepts 0V to 0.8V (logic low) or VBAT-0.8V to 5.5V (logic high) levels.
13 RXI input Inverted UART data input from microcontroller for half-duplex M-Bus communication, accepts 0V to 0.8V (logic low) or VBAT-0.8V to 5.5V (logic high) with ECHO feedback to TX/TXI.
14 RIS passive External current-setting resistor connection (100Ω to 1000Ω typical) that determines transmission current source CS3 modulation current IMC of 11.5mA to 19.5mA.
15 GND power_in Ground reference port providing 0V reference point for all voltage measurements and internal circuit return path.
16 BUSL1 bidirectional M-Bus interface port 1, part of ±50V differential pair for modulated half-duplex UART communication in both receive (voltage modulation detection) and transmit (current modulation) modes.

Key specifications

Parameter Value
Manufacturer Hangzhou Ruimeng Tech
Package SOP-16
Category Interface
Pins 16

CAD (KiCad official)

  • Symbol: MS721
  • Footprint: Package_SO:SOIC-16_3.9x9.9mm_P1.27mm
  • 3D model: SOP-16 (KiCad packages3D, STEP)
  • 3D model files: ms721-etched.step / ms721-etched.glb carry the MPN laser-etched on the die in a toggleable Adom.LaserEtch group (Fusion-ready); ms721.step / ms721.glb are the bare package body.

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

  • Datasheet: Hangzhou Ruimeng Tech datasheet (13 pp, sha256 6e4072a947be3631, retrieved 2026-09-22, tier: lcsc)
  • Datasheet language: Chinese. Pin names, descriptions, and specs on this page were extracted and translated to English by ds2sf; the linked PDF is the manufacturer original.
  • Extractor: parts-factory 2.0.0 / extract_pins 0.2, primary claude-haiku-4-5-20251001 (text), consensus claude-sonnet-4-6 (agreed), guards: pin_guards 0.1: passed. Pins are checked against the footprint pad set and their cited datasheet pages before publish.
  • CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF